xfs: pull up iolock from xfs_free_eofblocks()

xfs_free_eofblocks() requires the IOLOCK_EXCL lock, but is called from
different contexts where the lock may or may not be held. The
need_iolock parameter exists for this reason, to indicate whether
xfs_free_eofblocks() must acquire the iolock itself before it can
proceed.

This is ugly and confusing. Simplify the semantics of
xfs_free_eofblocks() to require the caller to acquire the iolock
appropriately and kill the need_iolock parameter. While here, the mp
param can be removed as well as the xfs_mount is accessible from the
xfs_inode structure. This patch does not change behavior.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index c141791..9319ee9 100644 (file)
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -917,17 +917,18 @@ xfs_can_free_eofblocks(struct xfs_inode *ip, bool force)
  */
 int
 xfs_free_eofblocks(
-       xfs_mount_t     *mp,
-       xfs_inode_t     *ip,
-       bool            need_iolock)
+       struct xfs_inode        *ip)
 {
-       xfs_trans_t     *tp;
-       int             error;
-       xfs_fileoff_t   end_fsb;
-       xfs_fileoff_t   last_fsb;
-       xfs_filblks_t   map_len;
-       int             nimaps;
-       xfs_bmbt_irec_t imap;
+       struct xfs_trans        *tp;
+       int                     error;
+       xfs_fileoff_t           end_fsb;
+       xfs_fileoff_t           last_fsb;
+       xfs_filblks_t           map_len;
+       int                     nimaps;
+       struct xfs_bmbt_irec    imap;
+       struct xfs_mount        *mp = ip->i_mount;
+
+       ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
 
        /*
         * Figure out if there are any blocks beyond the end
@@ -944,6 +945,10 @@ xfs_free_eofblocks(
        error = xfs_bmapi_read(ip, end_fsb, map_len, &imap, &nimaps, 0);
        xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
+       /*
+        * If there are blocks after the end of file, truncate the file to its
+        * current size to free them up.
+        */
        if (!error && (nimaps != 0) &&
            (imap.br_startblock != HOLESTARTBLOCK ||
             ip->i_delayed_blks)) {
@@ -954,22 +959,10 @@ xfs_free_eofblocks(
                if (error)
                        return error;
 
-               /*
-                * There are blocks after the end of file.
-                * Free them up now by truncating the file to
-                * its current size.
-                */
-               if (need_iolock) {
-                       if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL))
-                               return -EAGAIN;
-               }
-
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0,
                                &tp);
                if (error) {
                        ASSERT(XFS_FORCED_SHUTDOWN(mp));
-                       if (need_iolock)
-                               xfs_iunlock(ip, XFS_IOLOCK_EXCL);
                        return error;
                }
 
@@ -997,8 +990,6 @@ xfs_free_eofblocks(
                }
 
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
-               if (need_iolock)
-                       xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        }
        return error;
 }
@@ -1415,7 +1406,7 @@ xfs_shift_file_space(
         * into the accessible region of the file.
         */
        if (xfs_can_free_eofblocks(ip, true)) {
-               error = xfs_free_eofblocks(mp, ip, false);
+               error = xfs_free_eofblocks(ip);
                if (error)
                        return error;
        }

diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
index 68a621a..f100539 100644 (file)
--- a/fs/xfs/xfs_bmap_util.h
+++ b/fs/xfs/xfs_bmap_util.h
@@ -63,8 +63,7 @@ int   xfs_insert_file_space(struct xfs_inode *, xfs_off_t offset,
 
 /* EOF block manipulation functions */
 bool   xfs_can_free_eofblocks(struct xfs_inode *ip, bool force);
-int    xfs_free_eofblocks(struct xfs_mount *mp, struct xfs_inode *ip,
-                          bool need_iolock);
+int    xfs_free_eofblocks(struct xfs_inode *ip);
 
 int    xfs_swap_extents(struct xfs_inode *ip, struct xfs_inode *tip,
                         struct xfs_swapext *sx);

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 70ca4f6..c6b698f 100644 (file)
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1322,7 +1322,7 @@ xfs_inode_free_eofblocks(
        int                     flags,
        void                    *args)
 {
-       int ret;
+       int ret = 0;
        struct xfs_eofblocks *eofb = args;
        bool need_iolock = true;
        int match;
@@ -1358,19 +1358,25 @@ xfs_inode_free_eofblocks(
                        return 0;
 
                /*
-                * A scan owner implies we already hold the iolock. Skip it in
-                * xfs_free_eofblocks() to avoid deadlock. This also eliminates
-                * the possibility of EAGAIN being returned.
+                * A scan owner implies we already hold the iolock. Skip it here
+                * to avoid deadlock.
                 */
                if (eofb->eof_scan_owner == ip->i_ino)
                        need_iolock = false;
        }
 
-       ret = xfs_free_eofblocks(ip->i_mount, ip, need_iolock);
-
-       /* don't revisit the inode if we're not waiting */
-       if (ret == -EAGAIN && !(flags & SYNC_WAIT))
-               ret = 0;
+       /*
+        * If the caller is waiting, return -EAGAIN to keep the background
+        * scanner moving and revisit the inode in a subsequent pass.
+        */
+       if (need_iolock && !xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
+               if (flags & SYNC_WAIT)
+                       ret = -EAGAIN;
+               return ret;
+       }
+       ret = xfs_free_eofblocks(ip);
+       if (need_iolock)
+               xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 
        return ret;
 }

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index de32f0f..edfa6a5 100644 (file)
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1692,32 +1692,34 @@ xfs_release(
        if (xfs_can_free_eofblocks(ip, false)) {
 
                /*
+                * Check if the inode is being opened, written and closed
+                * frequently and we have delayed allocation blocks outstanding
+                * (e.g. streaming writes from the NFS server), truncating the
+                * blocks past EOF will cause fragmentation to occur.
+                *
+                * In this case don't do the truncation, but we have to be
+                * careful how we detect this case. Blocks beyond EOF show up as
+                * i_delayed_blks even when the inode is clean, so we need to
+                * truncate them away first before checking for a dirty release.
+                * Hence on the first dirty close we will still remove the
+                * speculative allocation, but after that we will leave it in
+                * place.
+                */
+               if (xfs_iflags_test(ip, XFS_IDIRTY_RELEASE))
+                       return 0;
+               /*
                 * If we can't get the iolock just skip truncating the blocks
                 * past EOF because we could deadlock with the mmap_sem
-                * otherwise.  We'll get another chance to drop them once the
+                * otherwise. We'll get another chance to drop them once the
                 * last reference to the inode is dropped, so we'll never leak
                 * blocks permanently.
-                *
-                * Further, check if the inode is being opened, written and
-                * closed frequently and we have delayed allocation blocks
-                * outstanding (e.g. streaming writes from the NFS server),
-                * truncating the blocks past EOF will cause fragmentation to
-                * occur.
-                *
-                * In this case don't do the truncation, either, but we have to
-                * be careful how we detect this case. Blocks beyond EOF show
-                * up as i_delayed_blks even when the inode is clean, so we
-                * need to truncate them away first before checking for a dirty
-                * release. Hence on the first dirty close we will still remove
-                * the speculative allocation, but after that we will leave it
-                * in place.
                 */
-               if (xfs_iflags_test(ip, XFS_IDIRTY_RELEASE))
-                       return 0;
-
-               error = xfs_free_eofblocks(mp, ip, true);
-               if (error && error != -EAGAIN)
-                       return error;
+               if (xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
+                       error = xfs_free_eofblocks(ip);
+                       xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+                       if (error)
+                               return error;
+               }
 
                /* delalloc blocks after truncation means it really is dirty */
                if (ip->i_delayed_blks)
@@ -1904,8 +1906,11 @@ xfs_inactive(
                 * cache. Post-eof blocks must be freed, lest we end up with
                 * broken free space accounting.
                 */
-               if (xfs_can_free_eofblocks(ip, true))
-                       xfs_free_eofblocks(mp, ip, false);
+               if (xfs_can_free_eofblocks(ip, true)) {
+                       xfs_ilock(ip, XFS_IOLOCK_EXCL);
+                       xfs_free_eofblocks(ip);
+                       xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+               }
 
                return;
        }