On Fri, May 10, 2024 at 10:39:06AM +0800, Chao Yu 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 > Looks like every COW filesystem would meet this situation. What's the solution of other FS? > This patch introduces a new per-inode i_opu_rwsem lock to avoid > such race condition. >
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