| Message ID | 20240627071521.1557830-1-chao@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 415ea641b020b7bbdf9b70bf241897ccbf7bf41f |
| Headers | show |
| Series | [f2fs-dev,v3] f2fs: fix to avoid racing in between read and OPU dio write | expand |
Hello: This patch was applied to jaegeuk/f2fs.git (dev) by Jaegeuk Kim <jaegeuk@kernel.org>: On Thu, 27 Jun 2024 15:15:21 +0800 you wrote: > 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 > > [...] Here is the summary with links: - [f2fs-dev,v3] f2fs: fix to avoid racing in between read and OPU dio write https://git.kernel.org/jaegeuk/f2fs/c/415ea641b020 You are awesome, thank you!
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 9e171e138943..76a6043caf27 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -4608,6 +4608,10 @@ 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 {
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> --- v3: - wait for direct IO's completion before read IO. fs/f2fs/file.c | 4 ++++ 1 file changed, 4 insertions(+)