From: Zhang Yi FALLOC_FL_WRITE_ZEROES requires that all blocks in the requested range end up as written extents with zeroed content. For unaligned edges that were partial-zeroed in dirty unwritten or delalloc state, the buffer is left dirty while the underlying extent may not yet be converted to written. As a result, a subsequent SYNC write to this range would still trigger metadata changes, which violates the semantics of WRITE_ZEROES. Fix this by calling filemap_write_and_wait_range() for partial-zeroed edges to flush out the zeroed data and ensure the extent conversion is complete. Fixes: f4265b8d32c4 ("ext4: add FALLOC_FL_WRITE_ZEROES support") Cc: stable@vger.kernel.org Signed-off-by: Zhang Yi Reviewed-by: Jan Kara --- fs/ext4/extents.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index c34505765521..c083703bf704 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4791,7 +4791,15 @@ static long ext4_zero_range(struct file *file, loff_t offset, if (IS_ALIGNED(offset | end, blocksize)) return ret; - if (((file->f_flags & O_SYNC) || IS_SYNC(inode)) && partial_zeroed) { + /* + * In FALLOC_FL_WRITE_ZEROES mode, edges that have been partially + * zeroed must be written back to ensure the entire zeroed range + * is converted to the written state. In SYNC mode, writeback is + * also required to persist the zeroed data to disk. + */ + if (partial_zeroed && + ((mode & FALLOC_FL_WRITE_ZEROES) || + (file->f_flags & O_SYNC) || IS_SYNC(inode))) { ret = filemap_write_and_wait_range(inode->i_mapping, offset, end - 1); if (ret) -- 2.52.0