Messages in this thread | | | Date | Thu, 30 Mar 2023 21:23:29 +0800 | From | Chao Yu <> | Subject | Re: [f2fs-dev] [PATCH] f2fs: get out of a repeat loop when getting a locked data page |
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On 2023/3/27 23:30, Jaegeuk Kim wrote: > On 03/26, Chao Yu wrote: >> On 2023/3/24 5:39, Jaegeuk Kim wrote: >>> https://bugzilla.kernel.org/show_bug.cgi?id=216050 >>> >>> Somehow we're getting a page which has a different mapping. >>> Let's avoid the infinite loop. >>> >>> Cc: <stable@vger.kernel.org> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> >>> --- >>> fs/f2fs/data.c | 8 ++------ >>> 1 file changed, 2 insertions(+), 6 deletions(-) >>> >>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>> index bf51e6e4eb64..80702c93e885 100644 >>> --- a/fs/f2fs/data.c >>> +++ b/fs/f2fs/data.c >>> @@ -1329,18 +1329,14 @@ struct page *f2fs_get_lock_data_page(struct inode *inode, pgoff_t index, >>> { >>> struct address_space *mapping = inode->i_mapping; >>> struct page *page; >>> -repeat: >>> + >>> page = f2fs_get_read_data_page(inode, index, 0, for_write, NULL); >>> if (IS_ERR(page)) >>> return page; >>> /* wait for read completion */ >>> lock_page(page); >>> - if (unlikely(page->mapping != mapping)) { >> >> How about using such logic only for move_data_page() to limit affect for >> other paths? > > Why move_data_page() only? If this happens, we'll fall into a loop in anywhere?
Actually, we only suffer dead loop from foreground GC path, right? I suspect the bug was triggered in this path only.
It looks there are a lot of cases in where we repeat triggering read once two mappings are mismatched, e.g. - __get_meta_page - __get_node_page - f2fs_write_begin - f2fs_quota_read
Thanks,
> >> >> Jaegeuk, any thoughts about why mapping is mismatch in between page's one and >> inode->i_mapping? > >> >> After several times code review, I didn't get any clue about why f2fs always >> get the different mapping in a loop. > > I couldn't find the path to happen this. So weird. Please check the history in the > bug. > >> >> Maybe we can loop MM guys to check whether below folio_file_page() may return >> page which has different mapping? > > Matthew may have some idea on this? > >> >> struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, >> int fgp_flags, gfp_t gfp) >> { >> struct folio *folio; >> >> folio = __filemap_get_folio(mapping, index, fgp_flags, gfp); >> if (IS_ERR(folio)) >> return NULL; >> return folio_file_page(folio, index); >> } >> >> Thanks, >> >>> - f2fs_put_page(page, 1); >>> - goto repeat; >>> - } >>> - if (unlikely(!PageUptodate(page))) { >>> + if (unlikely(page->mapping != mapping || !PageUptodate(page))) { >>> f2fs_put_page(page, 1); >>> return ERR_PTR(-EIO); >>> }
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