fix ITER_PIPE interaction with direct_IO

[platform/kernel/linux-exynos.git] / fs / xfs / xfs_file.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_error.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_ioctl.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_icache.h"
#include "xfs_pnfs.h"
#include "xfs_iomap.h"

#include <linux/dcache.h>
#include <linux/falloc.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>

static const struct vm_operations_struct xfs_file_vm_ops;

/*
 * Locking primitives for read and write IO paths to ensure we consistently use
 * and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
 */
static inline void
xfs_rw_ilock(
        struct xfs_inode        *ip,
        int                     type)
{
        if (type & XFS_IOLOCK_EXCL)
                inode_lock(VFS_I(ip));
        xfs_ilock(ip, type);
}

static inline void
xfs_rw_iunlock(
        struct xfs_inode        *ip,
        int                     type)
{
        xfs_iunlock(ip, type);
        if (type & XFS_IOLOCK_EXCL)
                inode_unlock(VFS_I(ip));
}

static inline void
xfs_rw_ilock_demote(
        struct xfs_inode        *ip,
        int                     type)
{
        xfs_ilock_demote(ip, type);
        if (type & XFS_IOLOCK_EXCL)
                inode_unlock(VFS_I(ip));
}

/*
 * Clear the specified ranges to zero through either the pagecache or DAX.
 * Holes and unwritten extents will be left as-is as they already are zeroed.
 */
int
xfs_zero_range(
        struct xfs_inode        *ip,
        xfs_off_t               pos,
        xfs_off_t               count,
        bool                    *did_zero)
{
        return iomap_zero_range(VFS_I(ip), pos, count, NULL, &xfs_iomap_ops);
}

int
xfs_update_prealloc_flags(
        struct xfs_inode        *ip,
        enum xfs_prealloc_flags flags)
{
        struct xfs_trans        *tp;
        int                     error;

        error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_writeid,
                        0, 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

        if (!(flags & XFS_PREALLOC_INVISIBLE)) {
                VFS_I(ip)->i_mode &= ~S_ISUID;
                if (VFS_I(ip)->i_mode & S_IXGRP)
                        VFS_I(ip)->i_mode &= ~S_ISGID;
                xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        }

        if (flags & XFS_PREALLOC_SET)
                ip->i_d.di_flags |= XFS_DIFLAG_PREALLOC;
        if (flags & XFS_PREALLOC_CLEAR)
                ip->i_d.di_flags &= ~XFS_DIFLAG_PREALLOC;

        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
        if (flags & XFS_PREALLOC_SYNC)
                xfs_trans_set_sync(tp);
        return xfs_trans_commit(tp);
}

/*
 * Fsync operations on directories are much simpler than on regular files,
 * as there is no file data to flush, and thus also no need for explicit
 * cache flush operations, and there are no non-transaction metadata updates
 * on directories either.
 */
STATIC int
xfs_dir_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct xfs_inode        *ip = XFS_I(file->f_mapping->host);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_lsn_t               lsn = 0;

        trace_xfs_dir_fsync(ip);

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip))
                lsn = ip->i_itemp->ili_last_lsn;
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        if (!lsn)
                return 0;
        return _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
}

STATIC int
xfs_file_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        int                     error = 0;
        int                     log_flushed = 0;
        xfs_lsn_t               lsn = 0;

        trace_xfs_file_fsync(ip);

        error = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (error)
                return error;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        xfs_iflags_clear(ip, XFS_ITRUNCATED);

        if (mp->m_flags & XFS_MOUNT_BARRIER) {
                /*
                 * If we have an RT and/or log subvolume we need to make sure
                 * to flush the write cache the device used for file data
                 * first.  This is to ensure newly written file data make
                 * it to disk before logging the new inode size in case of
                 * an extending write.
                 */
                if (XFS_IS_REALTIME_INODE(ip))
                        xfs_blkdev_issue_flush(mp->m_rtdev_targp);
                else if (mp->m_logdev_targp != mp->m_ddev_targp)
                        xfs_blkdev_issue_flush(mp->m_ddev_targp);
        }

        /*
         * All metadata updates are logged, which means that we just have to
         * flush the log up to the latest LSN that touched the inode. If we have
         * concurrent fsync/fdatasync() calls, we need them to all block on the
         * log force before we clear the ili_fsync_fields field. This ensures
         * that we don't get a racing sync operation that does not wait for the
         * metadata to hit the journal before returning. If we race with
         * clearing the ili_fsync_fields, then all that will happen is the log
         * force will do nothing as the lsn will already be on disk. We can't
         * race with setting ili_fsync_fields because that is done under
         * XFS_ILOCK_EXCL, and that can't happen because we hold the lock shared
         * until after the ili_fsync_fields is cleared.
         */
        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip)) {
                if (!datasync ||
                    (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
                        lsn = ip->i_itemp->ili_last_lsn;
        }

        if (lsn) {
                error = _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);
                ip->i_itemp->ili_fsync_fields = 0;
        }
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        /*
         * If we only have a single device, and the log force about was
         * a no-op we might have to flush the data device cache here.
         * This can only happen for fdatasync/O_DSYNC if we were overwriting
         * an already allocated file and thus do not have any metadata to
         * commit.
         */
        if ((mp->m_flags & XFS_MOUNT_BARRIER) &&
            mp->m_logdev_targp == mp->m_ddev_targp &&
            !XFS_IS_REALTIME_INODE(ip) &&
            !log_flushed)
                xfs_blkdev_issue_flush(mp->m_ddev_targp);

        return error;
}

STATIC ssize_t
xfs_file_dio_aio_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct address_space    *mapping = iocb->ki_filp->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        loff_t                  isize = i_size_read(inode);
        size_t                  count = iov_iter_count(to);
        struct iov_iter         data;
        struct xfs_buftarg      *target;
        ssize_t                 ret = 0;

        trace_xfs_file_direct_read(ip, count, iocb->ki_pos);

        if (!count)
                return 0; /* skip atime */

        if (XFS_IS_REALTIME_INODE(ip))
                target = ip->i_mount->m_rtdev_targp;
        else
                target = ip->i_mount->m_ddev_targp;

        /* DIO must be aligned to device logical sector size */
        if ((iocb->ki_pos | count) & target->bt_logical_sectormask) {
                if (iocb->ki_pos == isize)
                        return 0;
                return -EINVAL;
        }

        /*
         * Locking is a bit tricky here. If we take an exclusive lock for direct
         * IO, we effectively serialise all new concurrent read IO to this file
         * and block it behind IO that is currently in progress because IO in
         * progress holds the IO lock shared. We only need to hold the lock
         * exclusive to blow away the page cache, so only take lock exclusively
         * if the page cache needs invalidation. This allows the normal direct
         * IO case of no page cache pages to proceeed concurrently without
         * serialisation.
         */
        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
        if (mapping->nrpages) {
                xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
                xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);

                /*
                 * The generic dio code only flushes the range of the particular
                 * I/O. Because we take an exclusive lock here, this whole
                 * sequence is considerably more expensive for us. This has a
                 * noticeable performance impact for any file with cached pages,
                 * even when outside of the range of the particular I/O.
                 *
                 * Hence, amortize the cost of the lock against a full file
                 * flush and reduce the chances of repeated iolock cycles going
                 * forward.
                 */
                if (mapping->nrpages) {
                        ret = filemap_write_and_wait(mapping);
                        if (ret) {
                                xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
                                return ret;
                        }

                        /*
                         * Invalidate whole pages. This can return an error if
                         * we fail to invalidate a page, but this should never
                         * happen on XFS. Warn if it does fail.
                         */
                        ret = invalidate_inode_pages2(mapping);
                        WARN_ON_ONCE(ret);
                        ret = 0;
                }
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
        }

        data = *to;
        ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
                        xfs_get_blocks_direct, NULL, NULL, 0);
        if (ret >= 0) {
                iocb->ki_pos += ret;
                iov_iter_advance(to, ret);
        }
        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);

        file_accessed(iocb->ki_filp);
        return ret;
}

static noinline ssize_t
xfs_file_dax_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct address_space    *mapping = iocb->ki_filp->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct iov_iter         data = *to;
        size_t                  count = iov_iter_count(to);
        ssize_t                 ret = 0;

        trace_xfs_file_dax_read(ip, count, iocb->ki_pos);

        if (!count)
                return 0; /* skip atime */

        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
        ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct, NULL, 0);
        if (ret > 0) {
                iocb->ki_pos += ret;
                iov_iter_advance(to, ret);
        }
        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);

        file_accessed(iocb->ki_filp);
        return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct xfs_inode        *ip = XFS_I(file_inode(iocb->ki_filp));
        ssize_t                 ret;

        trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos);

        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
        ret = generic_file_read_iter(iocb, to);
        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);

        return ret;
}

STATIC ssize_t
xfs_file_read_iter(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct inode            *inode = file_inode(iocb->ki_filp);
        struct xfs_mount        *mp = XFS_I(inode)->i_mount;
        ssize_t                 ret = 0;

        XFS_STATS_INC(mp, xs_read_calls);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        if (IS_DAX(inode))
                ret = xfs_file_dax_read(iocb, to);
        else if (iocb->ki_flags & IOCB_DIRECT)
                ret = xfs_file_dio_aio_read(iocb, to);
        else
                ret = xfs_file_buffered_aio_read(iocb, to);

        if (ret > 0)
                XFS_STATS_ADD(mp, xs_read_bytes, ret);
        return ret;
}

/*
 * Zero any on disk space between the current EOF and the new, larger EOF.
 *
 * This handles the normal case of zeroing the remainder of the last block in
 * the file and the unusual case of zeroing blocks out beyond the size of the
 * file.  This second case only happens with fixed size extents and when the
 * system crashes before the inode size was updated but after blocks were
 * allocated.
 *
 * Expects the iolock to be held exclusive, and will take the ilock internally.
 */
int                                     /* error (positive) */
xfs_zero_eof(
        struct xfs_inode        *ip,
        xfs_off_t               offset,         /* starting I/O offset */
        xfs_fsize_t             isize,          /* current inode size */
        bool                    *did_zeroing)
{
        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(offset > isize);

        trace_xfs_zero_eof(ip, isize, offset - isize);
        return xfs_zero_range(ip, isize, offset - isize, did_zeroing);
}

/*
 * Common pre-write limit and setup checks.
 *
 * Called with the iolocked held either shared and exclusive according to
 * @iolock, and returns with it held.  Might upgrade the iolock to exclusive
 * if called for a direct write beyond i_size.
 */
STATIC ssize_t
xfs_file_aio_write_checks(
        struct kiocb            *iocb,
        struct iov_iter         *from,
        int                     *iolock)
{
        struct file             *file = iocb->ki_filp;
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 error = 0;
        size_t                  count = iov_iter_count(from);
        bool                    drained_dio = false;

restart:
        error = generic_write_checks(iocb, from);
        if (error <= 0)
                return error;

        error = xfs_break_layouts(inode, iolock, true);
        if (error)
                return error;

        /* For changing security info in file_remove_privs() we need i_mutex */
        if (*iolock == XFS_IOLOCK_SHARED && !IS_NOSEC(inode)) {
                xfs_rw_iunlock(ip, *iolock);
                *iolock = XFS_IOLOCK_EXCL;
                xfs_rw_ilock(ip, *iolock);
                goto restart;
        }
        /*
         * If the offset is beyond the size of the file, we need to zero any
         * blocks that fall between the existing EOF and the start of this
         * write.  If zeroing is needed and we are currently holding the
         * iolock shared, we need to update it to exclusive which implies
         * having to redo all checks before.
         *
         * We need to serialise against EOF updates that occur in IO
         * completions here. We want to make sure that nobody is changing the
         * size while we do this check until we have placed an IO barrier (i.e.
         * hold the XFS_IOLOCK_EXCL) that prevents new IO from being dispatched.
         * The spinlock effectively forms a memory barrier once we have the
         * XFS_IOLOCK_EXCL so we are guaranteed to see the latest EOF value
         * and hence be able to correctly determine if we need to run zeroing.
         */
        spin_lock(&ip->i_flags_lock);
        if (iocb->ki_pos > i_size_read(inode)) {
                bool    zero = false;

                spin_unlock(&ip->i_flags_lock);
                if (!drained_dio) {
                        if (*iolock == XFS_IOLOCK_SHARED) {
                                xfs_rw_iunlock(ip, *iolock);
                                *iolock = XFS_IOLOCK_EXCL;
                                xfs_rw_ilock(ip, *iolock);
                                iov_iter_reexpand(from, count);
                        }
                        /*
                         * We now have an IO submission barrier in place, but
                         * AIO can do EOF updates during IO completion and hence
                         * we now need to wait for all of them to drain. Non-AIO
                         * DIO will have drained before we are given the
                         * XFS_IOLOCK_EXCL, and so for most cases this wait is a
                         * no-op.
                         */
                        inode_dio_wait(inode);
                        drained_dio = true;
                        goto restart;
                }
                error = xfs_zero_eof(ip, iocb->ki_pos, i_size_read(inode), &zero);
                if (error)
                        return error;
        } else
                spin_unlock(&ip->i_flags_lock);

        /*
         * Updating the timestamps will grab the ilock again from
         * xfs_fs_dirty_inode, so we have to call it after dropping the
         * lock above.  Eventually we should look into a way to avoid
         * the pointless lock roundtrip.
         */
        if (likely(!(file->f_mode & FMODE_NOCMTIME))) {
                error = file_update_time(file);
                if (error)
                        return error;
        }

        /*
         * If we're writing the file then make sure to clear the setuid and
         * setgid bits if the process is not being run by root.  This keeps
         * people from modifying setuid and setgid binaries.
         */
        if (!IS_NOSEC(inode))
                return file_remove_privs(file);
        return 0;
}

/*
 * xfs_file_dio_aio_write - handle direct IO writes
 *
 * Lock the inode appropriately to prepare for and issue a direct IO write.
 * By separating it from the buffered write path we remove all the tricky to
 * follow locking changes and looping.
 *
 * If there are cached pages or we're extending the file, we need IOLOCK_EXCL
 * until we're sure the bytes at the new EOF have been zeroed and/or the cached
 * pages are flushed out.
 *
 * In most cases the direct IO writes will be done holding IOLOCK_SHARED
 * allowing them to be done in parallel with reads and other direct IO writes.
 * However, if the IO is not aligned to filesystem blocks, the direct IO layer
 * needs to do sub-block zeroing and that requires serialisation against other
 * direct IOs to the same block. In this case we need to serialise the
 * submission of the unaligned IOs so that we don't get racing block zeroing in
 * the dio layer.  To avoid the problem with aio, we also need to wait for
 * outstanding IOs to complete so that unwritten extent conversion is completed
 * before we try to map the overlapping block. This is currently implemented by
 * hitting it with a big hammer (i.e. inode_dio_wait()).
 *
 * Returns with locks held indicated by @iolock and errors indicated by
 * negative return values.
 */
STATIC ssize_t
xfs_file_dio_aio_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        ssize_t                 ret = 0;
        int                     unaligned_io = 0;
        int                     iolock;
        size_t                  count = iov_iter_count(from);
        loff_t                  end;
        struct iov_iter         data;
        struct xfs_buftarg      *target = XFS_IS_REALTIME_INODE(ip) ?
                                        mp->m_rtdev_targp : mp->m_ddev_targp;

        /* DIO must be aligned to device logical sector size */
        if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
                return -EINVAL;

        /* "unaligned" here means not aligned to a filesystem block */
        if ((iocb->ki_pos & mp->m_blockmask) ||
            ((iocb->ki_pos + count) & mp->m_blockmask))
                unaligned_io = 1;

        /*
         * We don't need to take an exclusive lock unless there page cache needs
         * to be invalidated or unaligned IO is being executed. We don't need to
         * consider the EOF extension case here because
         * xfs_file_aio_write_checks() will relock the inode as necessary for
         * EOF zeroing cases and fill out the new inode size as appropriate.
         */
        if (unaligned_io || mapping->nrpages)
                iolock = XFS_IOLOCK_EXCL;
        else
                iolock = XFS_IOLOCK_SHARED;
        xfs_rw_ilock(ip, iolock);

        /*
         * Recheck if there are cached pages that need invalidate after we got
         * the iolock to protect against other threads adding new pages while
         * we were waiting for the iolock.
         */
        if (mapping->nrpages && iolock == XFS_IOLOCK_SHARED) {
                xfs_rw_iunlock(ip, iolock);
                iolock = XFS_IOLOCK_EXCL;
                xfs_rw_ilock(ip, iolock);
        }

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;
        count = iov_iter_count(from);
        end = iocb->ki_pos + count - 1;

        /*
         * See xfs_file_dio_aio_read() for why we do a full-file flush here.
         */
        if (mapping->nrpages) {
                ret = filemap_write_and_wait(VFS_I(ip)->i_mapping);
                if (ret)
                        goto out;
                /*
                 * Invalidate whole pages. This can return an error if we fail
                 * to invalidate a page, but this should never happen on XFS.
                 * Warn if it does fail.
                 */
                ret = invalidate_inode_pages2(VFS_I(ip)->i_mapping);
                WARN_ON_ONCE(ret);
                ret = 0;
        }

        /*
         * If we are doing unaligned IO, wait for all other IO to drain,
         * otherwise demote the lock if we had to flush cached pages
         */
        if (unaligned_io)
                inode_dio_wait(inode);
        else if (iolock == XFS_IOLOCK_EXCL) {
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
                iolock = XFS_IOLOCK_SHARED;
        }

        trace_xfs_file_direct_write(ip, count, iocb->ki_pos);

        data = *from;
        ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
                        xfs_get_blocks_direct, xfs_end_io_direct_write,
                        NULL, DIO_ASYNC_EXTEND);

        /* see generic_file_direct_write() for why this is necessary */
        if (mapping->nrpages) {
                invalidate_inode_pages2_range(mapping,
                                              iocb->ki_pos >> PAGE_SHIFT,
                                              end >> PAGE_SHIFT);
        }

        if (ret > 0) {
                iocb->ki_pos += ret;
                iov_iter_advance(from, ret);
        }
out:
        xfs_rw_iunlock(ip, iolock);

        /*
         * No fallback to buffered IO on errors for XFS, direct IO will either
         * complete fully or fail.
         */
        ASSERT(ret < 0 || ret == count);
        return ret;
}

static noinline ssize_t
xfs_file_dax_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct address_space    *mapping = iocb->ki_filp->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        ssize_t                 ret = 0;
        int                     unaligned_io = 0;
        int                     iolock;
        struct iov_iter         data;

        /* "unaligned" here means not aligned to a filesystem block */
        if ((iocb->ki_pos & mp->m_blockmask) ||
            ((iocb->ki_pos + iov_iter_count(from)) & mp->m_blockmask)) {
                unaligned_io = 1;
                iolock = XFS_IOLOCK_EXCL;
        } else if (mapping->nrpages) {
                iolock = XFS_IOLOCK_EXCL;
        } else {
                iolock = XFS_IOLOCK_SHARED;
        }
        xfs_rw_ilock(ip, iolock);

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;

        /*
         * Yes, even DAX files can have page cache attached to them:  A zeroed
         * page is inserted into the pagecache when we have to serve a write
         * fault on a hole.  It should never be dirtied and can simply be
         * dropped from the pagecache once we get real data for the page.
         *
         * XXX: This is racy against mmap, and there's nothing we can do about
         * it. dax_do_io() should really do this invalidation internally as
         * it will know if we've allocated over a holei for this specific IO and
         * if so it needs to update the mapping tree and invalidate existing
         * PTEs over the newly allocated range. Remove this invalidation when
         * dax_do_io() is fixed up.
         */
        if (mapping->nrpages) {
                loff_t end = iocb->ki_pos + iov_iter_count(from) - 1;

                ret = invalidate_inode_pages2_range(mapping,
                                                    iocb->ki_pos >> PAGE_SHIFT,
                                                    end >> PAGE_SHIFT);
                WARN_ON_ONCE(ret);
        }

        if (iolock == XFS_IOLOCK_EXCL && !unaligned_io) {
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
                iolock = XFS_IOLOCK_SHARED;
        }

        trace_xfs_file_dax_write(ip, iov_iter_count(from), iocb->ki_pos);

        data = *from;
        ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct,
                        xfs_end_io_direct_write, 0);
        if (ret > 0) {
                iocb->ki_pos += ret;
                iov_iter_advance(from, ret);
        }
out:
        xfs_rw_iunlock(ip, iolock);
        return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        int                     enospc = 0;
        int                     iolock = XFS_IOLOCK_EXCL;

        xfs_rw_ilock(ip, iolock);

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;

        /* We can write back this queue in page reclaim */
        current->backing_dev_info = inode_to_bdi(inode);

write_retry:
        trace_xfs_file_buffered_write(ip, iov_iter_count(from), iocb->ki_pos);
        ret = iomap_file_buffered_write(iocb, from, &xfs_iomap_ops);
        if (likely(ret >= 0))
                iocb->ki_pos += ret;

        /*
         * If we hit a space limit, try to free up some lingering preallocated
         * space before returning an error. In the case of ENOSPC, first try to
         * write back all dirty inodes to free up some of the excess reserved
         * metadata space. This reduces the chances that the eofblocks scan
         * waits on dirty mappings. Since xfs_flush_inodes() is serialized, this
         * also behaves as a filter to prevent too many eofblocks scans from
         * running at the same time.
         */
        if (ret == -EDQUOT && !enospc) {
                enospc = xfs_inode_free_quota_eofblocks(ip);
                if (enospc)
                        goto write_retry;
        } else if (ret == -ENOSPC && !enospc) {
                struct xfs_eofblocks eofb = {0};

                enospc = 1;
                xfs_flush_inodes(ip->i_mount);
                eofb.eof_scan_owner = ip->i_ino; /* for locking */
                eofb.eof_flags = XFS_EOF_FLAGS_SYNC;
                xfs_icache_free_eofblocks(ip->i_mount, &eofb);
                goto write_retry;
        }

        current->backing_dev_info = NULL;
out:
        xfs_rw_iunlock(ip, iolock);
        return ret;
}

STATIC ssize_t
xfs_file_write_iter(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        size_t                  ocount = iov_iter_count(from);

        XFS_STATS_INC(ip->i_mount, xs_write_calls);

        if (ocount == 0)
                return 0;

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        if (IS_DAX(inode))
                ret = xfs_file_dax_write(iocb, from);
        else if (iocb->ki_flags & IOCB_DIRECT)
                ret = xfs_file_dio_aio_write(iocb, from);
        else
                ret = xfs_file_buffered_aio_write(iocb, from);

        if (ret > 0) {
                XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);

                /* Handle various SYNC-type writes */
                ret = generic_write_sync(iocb, ret);
        }
        return ret;
}

#define XFS_FALLOC_FL_SUPPORTED                                         \
                (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |           \
                 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |      \
                 FALLOC_FL_INSERT_RANGE)

STATIC long
xfs_file_fallocate(
        struct file             *file,
        int                     mode,
        loff_t                  offset,
        loff_t                  len)
{
        struct inode            *inode = file_inode(file);
        struct xfs_inode        *ip = XFS_I(inode);
        long                    error;
        enum xfs_prealloc_flags flags = 0;
        uint                    iolock = XFS_IOLOCK_EXCL;
        loff_t                  new_size = 0;
        bool                    do_file_insert = 0;

        if (!S_ISREG(inode->i_mode))
                return -EINVAL;
        if (mode & ~XFS_FALLOC_FL_SUPPORTED)
                return -EOPNOTSUPP;

        xfs_ilock(ip, iolock);
        error = xfs_break_layouts(inode, &iolock, false);
        if (error)
                goto out_unlock;

        xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
        iolock |= XFS_MMAPLOCK_EXCL;

        if (mode & FALLOC_FL_PUNCH_HOLE) {
                error = xfs_free_file_space(ip, offset, len);
                if (error)
                        goto out_unlock;
        } else if (mode & FALLOC_FL_COLLAPSE_RANGE) {
                unsigned blksize_mask = (1 << inode->i_blkbits) - 1;

                if (offset & blksize_mask || len & blksize_mask) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                /*
                 * There is no need to overlap collapse range with EOF,
                 * in which case it is effectively a truncate operation
                 */
                if (offset + len >= i_size_read(inode)) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                new_size = i_size_read(inode) - len;

                error = xfs_collapse_file_space(ip, offset, len);
                if (error)
                        goto out_unlock;
        } else if (mode & FALLOC_FL_INSERT_RANGE) {
                unsigned blksize_mask = (1 << inode->i_blkbits) - 1;

                new_size = i_size_read(inode) + len;
                if (offset & blksize_mask || len & blksize_mask) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                /* check the new inode size does not wrap through zero */
                if (new_size > inode->i_sb->s_maxbytes) {
                        error = -EFBIG;
                        goto out_unlock;
                }

                /* Offset should be less than i_size */
                if (offset >= i_size_read(inode)) {
                        error = -EINVAL;
                        goto out_unlock;
                }
                do_file_insert = 1;
        } else {
                flags |= XFS_PREALLOC_SET;

                if (!(mode & FALLOC_FL_KEEP_SIZE) &&
                    offset + len > i_size_read(inode)) {
                        new_size = offset + len;
                        error = inode_newsize_ok(inode, new_size);
                        if (error)
                                goto out_unlock;
                }

                if (mode & FALLOC_FL_ZERO_RANGE)
                        error = xfs_zero_file_space(ip, offset, len);
                else
                        error = xfs_alloc_file_space(ip, offset, len,
                                                     XFS_BMAPI_PREALLOC);
                if (error)
                        goto out_unlock;
        }

        if (file->f_flags & O_DSYNC)
                flags |= XFS_PREALLOC_SYNC;

        error = xfs_update_prealloc_flags(ip, flags);
        if (error)
                goto out_unlock;

        /* Change file size if needed */
        if (new_size) {
                struct iattr iattr;

                iattr.ia_valid = ATTR_SIZE;
                iattr.ia_size = new_size;
                error = xfs_setattr_size(ip, &iattr);
                if (error)
                        goto out_unlock;
        }

        /*
         * Perform hole insertion now that the file size has been
         * updated so that if we crash during the operation we don't
         * leave shifted extents past EOF and hence losing access to
         * the data that is contained within them.
         */
        if (do_file_insert)
                error = xfs_insert_file_space(ip, offset, len);

out_unlock:
        xfs_iunlock(ip, iolock);
        return error;
}


STATIC int
xfs_file_open(
        struct inode    *inode,
        struct file     *file)
{
        if (!(file->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
                return -EFBIG;
        if (XFS_FORCED_SHUTDOWN(XFS_M(inode->i_sb)))
                return -EIO;
        return 0;
}

STATIC int
xfs_dir_open(
        struct inode    *inode,
        struct file     *file)
{
        struct xfs_inode *ip = XFS_I(inode);
        int             mode;
        int             error;

        error = xfs_file_open(inode, file);
        if (error)
                return error;

        /*
         * If there are any blocks, read-ahead block 0 as we're almost
         * certain to have the next operation be a read there.
         */
        mode = xfs_ilock_data_map_shared(ip);
        if (ip->i_d.di_nextents > 0)
                xfs_dir3_data_readahead(ip, 0, -1);
        xfs_iunlock(ip, mode);
        return 0;
}

STATIC int
xfs_file_release(
        struct inode    *inode,
        struct file     *filp)
{
        return xfs_release(XFS_I(inode));
}

STATIC int
xfs_file_readdir(
        struct file     *file,
        struct dir_context *ctx)
{
        struct inode    *inode = file_inode(file);
        xfs_inode_t     *ip = XFS_I(inode);
        size_t          bufsize;

        /*
         * The Linux API doesn't pass down the total size of the buffer
         * we read into down to the filesystem.  With the filldir concept
         * it's not needed for correct information, but the XFS dir2 leaf
         * code wants an estimate of the buffer size to calculate it's
         * readahead window and size the buffers used for mapping to
         * physical blocks.
         *
         * Try to give it an estimate that's good enough, maybe at some
         * point we can change the ->readdir prototype to include the
         * buffer size.  For now we use the current glibc buffer size.
         */
        bufsize = (size_t)min_t(loff_t, 32768, ip->i_d.di_size);

        return xfs_readdir(ip, ctx, bufsize);
}

/*
 * This type is designed to indicate the type of offset we would like
 * to search from page cache for xfs_seek_hole_data().
 */
enum {
        HOLE_OFF = 0,
        DATA_OFF,
};

/*
 * Lookup the desired type of offset from the given page.
 *
 * On success, return true and the offset argument will point to the
 * start of the region that was found.  Otherwise this function will
 * return false and keep the offset argument unchanged.
 */
STATIC bool
xfs_lookup_buffer_offset(
        struct page             *page,
        loff_t                  *offset,
        unsigned int            type)
{
        loff_t                  lastoff = page_offset(page);
        bool                    found = false;
        struct buffer_head      *bh, *head;

        bh = head = page_buffers(page);
        do {
                /*
                 * Unwritten extents that have data in the page
                 * cache covering them can be identified by the
                 * BH_Unwritten state flag.  Pages with multiple
                 * buffers might have a mix of holes, data and
                 * unwritten extents - any buffer with valid
                 * data in it should have BH_Uptodate flag set
                 * on it.
                 */
                if (buffer_unwritten(bh) ||
                    buffer_uptodate(bh)) {
                        if (type == DATA_OFF)
                                found = true;
                } else {
                        if (type == HOLE_OFF)
                                found = true;
                }

                if (found) {
                        *offset = lastoff;
                        break;
                }
                lastoff += bh->b_size;
        } while ((bh = bh->b_this_page) != head);

        return found;
}

/*
 * This routine is called to find out and return a data or hole offset
 * from the page cache for unwritten extents according to the desired
 * type for xfs_seek_hole_data().
 *
 * The argument offset is used to tell where we start to search from the
 * page cache.  Map is used to figure out the end points of the range to
 * lookup pages.
 *
 * Return true if the desired type of offset was found, and the argument
 * offset is filled with that address.  Otherwise, return false and keep
 * offset unchanged.
 */
STATIC bool
xfs_find_get_desired_pgoff(
        struct inode            *inode,
        struct xfs_bmbt_irec    *map,
        unsigned int            type,
        loff_t                  *offset)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct pagevec          pvec;
        pgoff_t                 index;
        pgoff_t                 end;
        loff_t                  endoff;
        loff_t                  startoff = *offset;
        loff_t                  lastoff = startoff;
        bool                    found = false;

        pagevec_init(&pvec, 0);

        index = startoff >> PAGE_SHIFT;
        endoff = XFS_FSB_TO_B(mp, map->br_startoff + map->br_blockcount);
        end = endoff >> PAGE_SHIFT;
        do {
                int             want;
                unsigned        nr_pages;
                unsigned int    i;

                want = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
                nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
                                          want);
                /*
                 * No page mapped into given range.  If we are searching holes
                 * and if this is the first time we got into the loop, it means
                 * that the given offset is landed in a hole, return it.
                 *
                 * If we have already stepped through some block buffers to find
                 * holes but they all contains data.  In this case, the last
                 * offset is already updated and pointed to the end of the last
                 * mapped page, if it does not reach the endpoint to search,
                 * that means there should be a hole between them.
                 */
                if (nr_pages == 0) {
                        /* Data search found nothing */
                        if (type == DATA_OFF)
                                break;

                        ASSERT(type == HOLE_OFF);
                        if (lastoff == startoff || lastoff < endoff) {
                                found = true;
                                *offset = lastoff;
                        }
                        break;
                }

                /*
                 * At lease we found one page.  If this is the first time we
                 * step into the loop, and if the first page index offset is
                 * greater than the given search offset, a hole was found.
                 */
                if (type == HOLE_OFF && lastoff == startoff &&
                    lastoff < page_offset(pvec.pages[0])) {
                        found = true;
                        break;
                }

                for (i = 0; i < nr_pages; i++) {
                        struct page     *page = pvec.pages[i];
                        loff_t          b_offset;

                        /*
                         * At this point, the page may be truncated or
                         * invalidated (changing page->mapping to NULL),
                         * or even swizzled back from swapper_space to tmpfs
                         * file mapping. However, page->index will not change
                         * because we have a reference on the page.
                         *
                         * Searching done if the page index is out of range.
                         * If the current offset is not reaches the end of
                         * the specified search range, there should be a hole
                         * between them.
                         */
                        if (page->index > end) {
                                if (type == HOLE_OFF && lastoff < endoff) {
                                        *offset = lastoff;
                                        found = true;
                                }
                                goto out;
                        }

                        lock_page(page);
                        /*
                         * Page truncated or invalidated(page->mapping == NULL).
                         * We can freely skip it and proceed to check the next
                         * page.
                         */
                        if (unlikely(page->mapping != inode->i_mapping)) {
                                unlock_page(page);
                                continue;
                        }

                        if (!page_has_buffers(page)) {
                                unlock_page(page);
                                continue;
                        }

                        found = xfs_lookup_buffer_offset(page, &b_offset, type);
                        if (found) {
                                /*
                                 * The found offset may be less than the start
                                 * point to search if this is the first time to
                                 * come here.
                                 */
                                *offset = max_t(loff_t, startoff, b_offset);
                                unlock_page(page);
                                goto out;
                        }

                        /*
                         * We either searching data but nothing was found, or
                         * searching hole but found a data buffer.  In either
                         * case, probably the next page contains the desired
                         * things, update the last offset to it so.
                         */
                        lastoff = page_offset(page) + PAGE_SIZE;
                        unlock_page(page);
                }

                /*
                 * The number of returned pages less than our desired, search
                 * done.  In this case, nothing was found for searching data,
                 * but we found a hole behind the last offset.
                 */
                if (nr_pages < want) {
                        if (type == HOLE_OFF) {
                                *offset = lastoff;
                                found = true;
                        }
                        break;
                }

                index = pvec.pages[i - 1]->index + 1;
                pagevec_release(&pvec);
        } while (index <= end);

out:
        pagevec_release(&pvec);
        return found;
}

/*
 * caller must lock inode with xfs_ilock_data_map_shared,
 * can we craft an appropriate ASSERT?
 *
 * end is because the VFS-level lseek interface is defined such that any
 * offset past i_size shall return -ENXIO, but we use this for quota code
 * which does not maintain i_size, and we want to SEEK_DATA past i_size.
 */
loff_t
__xfs_seek_hole_data(
        struct inode            *inode,
        loff_t                  start,
        loff_t                  end,
        int                     whence)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        loff_t                  uninitialized_var(offset);
        xfs_fileoff_t           fsbno;
        xfs_filblks_t           lastbno;
        int                     error;

        if (start >= end) {
                error = -ENXIO;
                goto out_error;
        }

        /*
         * Try to read extents from the first block indicated
         * by fsbno to the end block of the file.
         */
        fsbno = XFS_B_TO_FSBT(mp, start);
        lastbno = XFS_B_TO_FSB(mp, end);

        for (;;) {
                struct xfs_bmbt_irec    map[2];
                int                     nmap = 2;
                unsigned int            i;

                error = xfs_bmapi_read(ip, fsbno, lastbno - fsbno, map, &nmap,
                                       XFS_BMAPI_ENTIRE);
                if (error)
                        goto out_error;

                /* No extents at given offset, must be beyond EOF */
                if (nmap == 0) {
                        error = -ENXIO;
                        goto out_error;
                }

                for (i = 0; i < nmap; i++) {
                        offset = max_t(loff_t, start,
                                       XFS_FSB_TO_B(mp, map[i].br_startoff));

                        /* Landed in the hole we wanted? */
                        if (whence == SEEK_HOLE &&
                            map[i].br_startblock == HOLESTARTBLOCK)
                                goto out;

                        /* Landed in the data extent we wanted? */
                        if (whence == SEEK_DATA &&
                            (map[i].br_startblock == DELAYSTARTBLOCK ||
                             (map[i].br_state == XFS_EXT_NORM &&
                              !isnullstartblock(map[i].br_startblock))))
                                goto out;

                        /*
                         * Landed in an unwritten extent, try to search
                         * for hole or data from page cache.
                         */
                        if (map[i].br_state == XFS_EXT_UNWRITTEN) {
                                if (xfs_find_get_desired_pgoff(inode, &map[i],
                                      whence == SEEK_HOLE ? HOLE_OFF : DATA_OFF,
                                                        &offset))
                                        goto out;
                        }
                }

                /*
                 * We only received one extent out of the two requested. This
                 * means we've hit EOF and didn't find what we are looking for.
                 */
                if (nmap == 1) {
                        /*
                         * If we were looking for a hole, set offset to
                         * the end of the file (i.e., there is an implicit
                         * hole at the end of any file).
                         */
                        if (whence == SEEK_HOLE) {
                                offset = end;
                                break;
                        }
                        /*
                         * If we were looking for data, it's nowhere to be found
                         */
                        ASSERT(whence == SEEK_DATA);
                        error = -ENXIO;
                        goto out_error;
                }

                ASSERT(i > 1);

                /*
                 * Nothing was found, proceed to the next round of search
                 * if the next reading offset is not at or beyond EOF.
                 */
                fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
                start = XFS_FSB_TO_B(mp, fsbno);
                if (start >= end) {
                        if (whence == SEEK_HOLE) {
                                offset = end;
                                break;
                        }
                        ASSERT(whence == SEEK_DATA);
                        error = -ENXIO;
                        goto out_error;
                }
        }

out:
        /*
         * If at this point we have found the hole we wanted, the returned
         * offset may be bigger than the file size as it may be aligned to
         * page boundary for unwritten extents.  We need to deal with this
         * situation in particular.
         */
        if (whence == SEEK_HOLE)
                offset = min_t(loff_t, offset, end);

        return offset;

out_error:
        return error;
}

STATIC loff_t
xfs_seek_hole_data(
        struct file             *file,
        loff_t                  start,
        int                     whence)
{
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        uint                    lock;
        loff_t                  offset, end;
        int                     error = 0;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        lock = xfs_ilock_data_map_shared(ip);

        end = i_size_read(inode);
        offset = __xfs_seek_hole_data(inode, start, end, whence);
        if (offset < 0) {
                error = offset;
                goto out_unlock;
        }

        offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);

out_unlock:
        xfs_iunlock(ip, lock);

        if (error)
                return error;
        return offset;
}

STATIC loff_t
xfs_file_llseek(
        struct file     *file,
        loff_t          offset,
        int             whence)
{
        switch (whence) {
        case SEEK_END:
        case SEEK_CUR:
        case SEEK_SET:
                return generic_file_llseek(file, offset, whence);
        case SEEK_HOLE:
        case SEEK_DATA:
                return xfs_seek_hole_data(file, offset, whence);
        default:
                return -EINVAL;
        }
}

/*
 * Locking for serialisation of IO during page faults. This results in a lock
 * ordering of:
 *
 * mmap_sem (MM)
 *   sb_start_pagefault(vfs, freeze)
 *     i_mmaplock (XFS - truncate serialisation)
 *       page_lock (MM)
 *         i_lock (XFS - extent map serialisation)
 */

/*
 * mmap()d file has taken write protection fault and is being made writable. We
 * can set the page state up correctly for a writable page, which means we can
 * do correct delalloc accounting (ENOSPC checking!) and unwritten extent
 * mapping.
 */
STATIC int
xfs_filemap_page_mkwrite(
        struct vm_area_struct   *vma,
        struct vm_fault         *vmf)
{
        struct inode            *inode = file_inode(vma->vm_file);
        int                     ret;

        trace_xfs_filemap_page_mkwrite(XFS_I(inode));

        sb_start_pagefault(inode->i_sb);
        file_update_time(vma->vm_file);
        xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);

        if (IS_DAX(inode)) {
                ret = dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault);
        } else {
                ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
                ret = block_page_mkwrite_return(ret);
        }

        xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
        sb_end_pagefault(inode->i_sb);

        return ret;
}

STATIC int
xfs_filemap_fault(
        struct vm_area_struct   *vma,
        struct vm_fault         *vmf)
{
        struct inode            *inode = file_inode(vma->vm_file);
        int                     ret;

        trace_xfs_filemap_fault(XFS_I(inode));

        /* DAX can shortcut the normal fault path on write faults! */
        if ((vmf->flags & FAULT_FLAG_WRITE) && IS_DAX(inode))
                return xfs_filemap_page_mkwrite(vma, vmf);

        xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
        if (IS_DAX(inode)) {
                /*
                 * we do not want to trigger unwritten extent conversion on read
                 * faults - that is unnecessary overhead and would also require
                 * changes to xfs_get_blocks_direct() to map unwritten extent
                 * ioend for conversion on read-only mappings.
                 */
                ret = dax_fault(vma, vmf, xfs_get_blocks_dax_fault);
        } else
                ret = filemap_fault(vma, vmf);
        xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);

        return ret;
}

/*
 * Similar to xfs_filemap_fault(), the DAX fault path can call into here on
 * both read and write faults. Hence we need to handle both cases. There is no
 * ->pmd_mkwrite callout for huge pages, so we have a single function here to
 * handle both cases here. @flags carries the information on the type of fault
 * occuring.
 */
STATIC int
xfs_filemap_pmd_fault(
        struct vm_area_struct   *vma,
        unsigned long           addr,
        pmd_t                   *pmd,
        unsigned int            flags)
{
        struct inode            *inode = file_inode(vma->vm_file);
        struct xfs_inode        *ip = XFS_I(inode);
        int                     ret;

        if (!IS_DAX(inode))
                return VM_FAULT_FALLBACK;

        trace_xfs_filemap_pmd_fault(ip);

        if (flags & FAULT_FLAG_WRITE) {
                sb_start_pagefault(inode->i_sb);
                file_update_time(vma->vm_file);
        }

        xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
        ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
        xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);

        if (flags & FAULT_FLAG_WRITE)
                sb_end_pagefault(inode->i_sb);

        return ret;
}

/*
 * pfn_mkwrite was originally inteneded to ensure we capture time stamp
 * updates on write faults. In reality, it's need to serialise against
 * truncate similar to page_mkwrite. Hence we cycle the XFS_MMAPLOCK_SHARED
 * to ensure we serialise the fault barrier in place.
 */
static int
xfs_filemap_pfn_mkwrite(
        struct vm_area_struct   *vma,
        struct vm_fault         *vmf)
{

        struct inode            *inode = file_inode(vma->vm_file);
        struct xfs_inode        *ip = XFS_I(inode);
        int                     ret = VM_FAULT_NOPAGE;
        loff_t                  size;

        trace_xfs_filemap_pfn_mkwrite(ip);

        sb_start_pagefault(inode->i_sb);
        file_update_time(vma->vm_file);

        /* check if the faulting page hasn't raced with truncate */
        xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
        if (vmf->pgoff >= size)
                ret = VM_FAULT_SIGBUS;
        else if (IS_DAX(inode))
                ret = dax_pfn_mkwrite(vma, vmf);
        xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
        sb_end_pagefault(inode->i_sb);
        return ret;

}

static const struct vm_operations_struct xfs_file_vm_ops = {
        .fault          = xfs_filemap_fault,
        .pmd_fault      = xfs_filemap_pmd_fault,
        .map_pages      = filemap_map_pages,
        .page_mkwrite   = xfs_filemap_page_mkwrite,
        .pfn_mkwrite    = xfs_filemap_pfn_mkwrite,
};

STATIC int
xfs_file_mmap(
        struct file     *filp,
        struct vm_area_struct *vma)
{
        file_accessed(filp);
        vma->vm_ops = &xfs_file_vm_ops;
        if (IS_DAX(file_inode(filp)))
                vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
        return 0;
}

const struct file_operations xfs_file_operations = {
        .llseek         = xfs_file_llseek,
        .read_iter      = xfs_file_read_iter,
        .write_iter     = xfs_file_write_iter,
        .splice_read    = generic_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .mmap           = xfs_file_mmap,
        .open           = xfs_file_open,
        .release        = xfs_file_release,
        .fsync          = xfs_file_fsync,
        .fallocate      = xfs_file_fallocate,
};

const struct file_operations xfs_dir_file_operations = {
        .open           = xfs_dir_open,
        .read           = generic_read_dir,
        .iterate_shared = xfs_file_readdir,
        .llseek         = generic_file_llseek,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .fsync          = xfs_dir_fsync,
};