fuse: Trust kernel i_size only

Make fuse think that when writeback is on the inode's i_size is always
up-to-date and not update it with the value received from the userspace.
This is done because the page cache code may update i_size without letting
the FS know.

This assumption implies fixing the previously introduced short-read helper --
when a short read occurs the 'hole' is filled with zeroes.

fuse_file_fallocate() is also fixed because now we should keep i_size up to
date, so it must be updated if FUSE_FALLOCATE request succeeded.

Signed-off-by: Maxim V. Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 1d1292c..c52f143 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -839,6 +839,11 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
                          struct kstat *stat)
 {
        unsigned int blkbits;
+       struct fuse_conn *fc = get_fuse_conn(inode);
+
+       /* see the comment in fuse_change_attributes() */
+       if (fc->writeback_cache && S_ISREG(inode->i_mode))
+               attr->size = i_size_read(inode);
 
        stat->dev = inode->i_sb->s_dev;
        stat->ino = attr->ino;
@@ -1580,6 +1585,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
        struct fuse_setattr_in inarg;
        struct fuse_attr_out outarg;
        bool is_truncate = false;
+       bool is_wb = fc->writeback_cache;
        loff_t oldsize;
        int err;
 
@@ -1651,7 +1657,9 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
        fuse_change_attributes_common(inode, &outarg.attr,
                                      attr_timeout(&outarg));
        oldsize = inode->i_size;
-       i_size_write(inode, outarg.attr.size);
+       /* see the comment in fuse_change_attributes() */
+       if (!is_wb || is_truncate || !S_ISREG(inode->i_mode))
+               i_size_write(inode, outarg.attr.size);
 
        if (is_truncate) {
                /* NOTE: this may release/reacquire fc->lock */
@@ -1663,7 +1671,8 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
         * Only call invalidate_inode_pages2() after removing
         * FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.
         */
-       if (S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
+       if ((is_truncate || !is_wb) &&
+           S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
                truncate_pagecache(inode, outarg.attr.size);
                invalidate_inode_pages2(inode->i_mapping);
        }

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 592d7b4..c091a17 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -675,9 +675,26 @@ static void fuse_short_read(struct fuse_req *req, struct inode *inode,
                            u64 attr_ver)
 {
        size_t num_read = req->out.args[0].size;
+       struct fuse_conn *fc = get_fuse_conn(inode);
+
+       if (fc->writeback_cache) {
+               /*
+                * A hole in a file. Some data after the hole are in page cache,
+                * but have not reached the client fs yet. So, the hole is not
+                * present there.
+                */
+               int i;
+               int start_idx = num_read >> PAGE_CACHE_SHIFT;
+               size_t off = num_read & (PAGE_CACHE_SIZE - 1);
 
-       loff_t pos = page_offset(req->pages[0]) + num_read;
-       fuse_read_update_size(inode, pos, attr_ver);
+               for (i = start_idx; i < req->num_pages; i++) {
+                       zero_user_segment(req->pages[i], off, PAGE_CACHE_SIZE);
+                       off = 0;
+               }
+       } else {
+               loff_t pos = page_offset(req->pages[0]) + num_read;
+               fuse_read_update_size(inode, pos, attr_ver);
+       }
 }
 
 static int fuse_readpage(struct file *file, struct page *page)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index d468643..c668c84 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -197,6 +197,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 {
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);
+       bool is_wb = fc->writeback_cache;
        loff_t oldsize;
        struct timespec old_mtime;
 
@@ -211,10 +212,16 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
        fuse_change_attributes_common(inode, attr, attr_valid);
 
        oldsize = inode->i_size;
-       i_size_write(inode, attr->size);
+       /*
+        * In case of writeback_cache enabled, the cached writes beyond EOF
+        * extend local i_size without keeping userspace server in sync. So,
+        * attr->size coming from server can be stale. We cannot trust it.
+        */
+       if (!is_wb || !S_ISREG(inode->i_mode))
+               i_size_write(inode, attr->size);
        spin_unlock(&fc->lock);
 
-       if (S_ISREG(inode->i_mode)) {
+       if (!is_wb && S_ISREG(inode->i_mode)) {
                bool inval = false;
 
                if (oldsize != attr->size) {