4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Goldwyn Rodrigues <[email protected]> commit 0b34c261e235a5c74dcf78bd305845bd15fe2b42 upstream. While free'ing qgroup->reserved resources, we much check if the page has not been invalidated by a truncate operation by checking if the page is still dirty before reducing the qgroup resources. Resources in such a case are free'd when the entire extent is released by delayed_ref. This fixes a double accounting while releasing resources in case of truncating a file, reproduced by the following testcase. SCRATCH_DEV=/dev/vdb SCRATCH_MNT=/mnt mkfs.btrfs -f $SCRATCH_DEV mount -t btrfs $SCRATCH_DEV $SCRATCH_MNT cd $SCRATCH_MNT btrfs quota enable $SCRATCH_MNT btrfs subvolume create a btrfs qgroup limit 500m a $SCRATCH_MNT sync for c in {1..15}; do dd if=/dev/zero bs=1M count=40 of=$SCRATCH_MNT/a/file; done sleep 10 sync sleep 5 touch $SCRATCH_MNT/a/newfile echo "Removing file" rm $SCRATCH_MNT/a/file Fixes: b9d0b38928 ("btrfs: Add handler for invalidate page") Signed-off-by: Goldwyn Rodrigues <[email protected]> Reviewed-by: Qu Wenruo <[email protected]> Signed-off-by: David Sterba <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/btrfs/inode.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8915,9 +8915,14 @@ again: * So even we call qgroup_free_data(), it won't decrease reserved * space. * 2) Not written to disk - * This means the reserved space should be freed here. + * This means the reserved space should be freed here. However, + * if a truncate invalidates the page (by clearing PageDirty) + * and the page is accounted for while allocating extent + * in btrfs_check_data_free_space() we let delayed_ref to + * free the entire extent. */ - btrfs_qgroup_free_data(inode, page_start, PAGE_SIZE); + if (PageDirty(page)) + btrfs_qgroup_free_data(inode, page_start, PAGE_SIZE); if (!inode_evicting) { clear_extent_bit(tree, page_start, page_end, EXTENT_LOCKED | EXTENT_DIRTY |
