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authorJosef Bacik <josef@redhat.com>2012-06-19 10:59:00 -0400
committerChris Mason <chris.mason@fusionio.com>2012-07-02 15:36:23 -0400
commitc3473e830074ef04f974f2829690942dd8580619 (patch)
tree21e5e5117bffcf4cdb01e6985346747aeccd331e /fs/btrfs/file.c
parent597a60fadedf9a40fdff8735054bf772b3dafd57 (diff)
Btrfs: fix dio write vs buffered read race
Miao pointed out there's a problem with mixing dio writes and buffered reads. If the read happens between us invalidating the page range and actually locking the extent we can bring in pages into page cache. Then once the write finishes if somebody tries to read again it will just find uptodate pages and we'll read stale data. So we need to lock the extent and check for uptodate bits in the range. If there are uptodate bits we need to unlock and invalidate again. This will keep this race from happening since we will hold the extent locked until we create the ordered extent, and then teh read side always waits for ordered extents. There was also a race in how we updated i_size, previously we were relying on the generic DIO stuff to adjust the i_size after the DIO had completed, but this happens outside of the extent lock which means reads could come in and not see the updated i_size. So instead move this work into where we create the extents, and then this way the update ordered i_size stuff works properly in the endio handlers. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
Diffstat (limited to 'fs/btrfs/file.c')
-rw-r--r--fs/btrfs/file.c13
1 files changed, 0 insertions, 13 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 876cddd6b2f0..248d20265249 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1334,7 +1334,6 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,
loff_t *ppos, size_t count, size_t ocount)
{
struct file *file = iocb->ki_filp;
- struct inode *inode = fdentry(file)->d_inode;
struct iov_iter i;
ssize_t written;
ssize_t written_buffered;
@@ -1344,18 +1343,6 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,
written = generic_file_direct_write(iocb, iov, &nr_segs, pos, ppos,
count, ocount);
- /*
- * the generic O_DIRECT will update in-memory i_size after the
- * DIOs are done. But our endio handlers that update the on
- * disk i_size never update past the in memory i_size. So we
- * need one more update here to catch any additions to the
- * file
- */
- if (inode->i_size != BTRFS_I(inode)->disk_i_size) {
- btrfs_ordered_update_i_size(inode, inode->i_size, NULL);
- mark_inode_dirty(inode);
- }
-
if (written < 0 || written == count)
return written;