6.6-stable review patch. If anyone has any objections, please let me know.
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From: Chao Yu chao@kernel.org
[ Upstream commit 0cac51185e65dc2a20686184e02f3cafc99eb202 ]
If lfs mode is on, buffered read may race w/ OPU dio write as below, it may cause buffered read hits unwritten data unexpectly, and for dio read, the race condition exists as well.
Thread A Thread B - f2fs_file_write_iter - f2fs_dio_write_iter - __iomap_dio_rw - f2fs_iomap_begin - f2fs_map_blocks - __allocate_data_block - allocated blkaddr #x - iomap_dio_submit_bio - f2fs_file_read_iter - filemap_read - f2fs_read_data_folio - f2fs_mpage_readpages - f2fs_map_blocks : get blkaddr #x - f2fs_submit_read_bio IRQ - f2fs_read_end_io : read IO on blkaddr #x complete IRQ - iomap_dio_bio_end_io : direct write IO on blkaddr #x complete
In LFS mode, if there is inflight dio, let's wait for its completion, this policy won't cover all race cases, however it is a tradeoff which avoids abusing lock around IO paths.
Fixes: f847c699cff3 ("f2fs: allow out-place-update for direct IO in LFS mode") Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/f2fs/file.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 81e342bd993c2..8c4c5c6c1ac64 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -4541,6 +4541,10 @@ static ssize_t f2fs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) f2fs_trace_rw_file_path(iocb->ki_filp, iocb->ki_pos, iov_iter_count(to), READ);
+ /* In LFS mode, if there is inflight dio, wait for its completion */ + if (f2fs_lfs_mode(F2FS_I_SB(inode))) + inode_dio_wait(inode); + if (f2fs_should_use_dio(inode, iocb, to)) { ret = f2fs_dio_read_iter(iocb, to); } else {