On 04/10, Chao Yu wrote: > On 2023/4/6 11:18, Jaegeuk Kim wrote: > > On 04/06, Chao Yu wrote: > > > On 2023/4/6 0:39, Jaegeuk Kim wrote: > > > > On 03/27, Matthew Wilcox wrote: > > > > > On Mon, Mar 27, 2023 at 08:30:33AM -0700, 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@xxxxxxxxxxxxxxx> > > > > > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> > > > > > > > > --- > > > > > > > > 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? > > > > > > > > > > > > > > > > > > > > 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? > > > > > > > > > > There's a lot of comments in the bug ... hard to come into this one > > > > > cold. > > > > > > > > > > I did notice this one (#119): > > > > > : Interestingly, ref count is 514, which looks suspiciously as a binary > > > > > : flag 1000000010. Is it possible that during 5.17/5.18 implementation > > > > > : of a "pin", somehow binary flag was written to ref count, or something > > > > > : like '1 << ...' happens? > > > > > > > > > > That indicates to me that somehow you've got hold of a THP that is in > > > > > the page cache. Probably shmem/tmpfs. That indicate to me a refcount > > > > > problem that looks something like this: > > > > > > > > > > f2fs allocates a page > > > > > f2fs adds the page to the page cache > > > > > f2fs puts the reference to the page without removing it from the > > > > > page cache (how?) > > > > > > > > Is it somewhat related to setting a bit in private field? > > > > > > IIUC, it looks the page reference is added/removed as pair. > > > > > > > > > > > When we migrate the blocks, we do: > > > > 1) get_lock_page() > > > > > > - f2fs_grab_cache_page > > > - pagecache_get_page > > > - __filemap_get_folio > > > - no_page -> filemap_alloc_folio page_ref = 1 (referenced by caller) > > > - filemap_add_folio page_ref = 2 (referenced by radix tree) > > > > > > > 2) submit read > > > > 3) lock_page() > > > > 3) set_page_dirty() > > > > 4) set_page_private_gcing(page) > > > > > > page_ref = 3 (reference by private data) > > > > > > > > > > > --- in fs/f2fs/f2fs.h > > > > 1409 #define PAGE_PRIVATE_SET_FUNC(name, flagname) \ > > > > 1410 static inline void set_page_private_##name(struct page *page) \ > > > > 1411 { \ > > > > 1412 if (!PagePrivate(page)) { \ > > > > 1413 get_page(page); \ > > > > 1414 SetPagePrivate(page); \ > > > > 1415 set_page_private(page, 0); \ > > > > 1416 } \ > > > > 1417 set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); \ > > > > 1418 set_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \ > > > > 1419 } > > > > > > > > > > > > 5) set_page_writebac() > > > > 6) submit write > > > > 7) unlock_page() > > > > 8) put_page(page) > > > > > > page_ref = 2 (ref by caller was removed) > > > > > > > > > > > Later, f2fs_invalidate_folio will do put_page again by: > > > > clear_page_private_gcing(&folio->page); > > > > > > page_ref = 1 (ref by private was removed, and the last left ref is hold by radix tree) > > > > > > > > > > > --- in fs/f2fs/f2fs.h > > > > 1421 #define PAGE_PRIVATE_CLEAR_FUNC(name, flagname) \ > > > > 1422 static inline void clear_page_private_##name(struct page *page) \ > > > > 1423 { \ > > > > 1424 clear_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \ > > > > 1425 if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) { \ > > > > 1426 set_page_private(page, 0); \ > > > > 1427 if (PagePrivate(page)) { \ > > > > 1428 ClearPagePrivate(page); \ > > > > > > Since PagePrivate was cleared, so folio_detach_private in > > > f2fs_invalidate_folio()/f2fs_release_folio will just skip drop reference. > > > > > > static inline void *folio_detach_private(struct folio *folio) > > > { > > > void *data = folio_get_private(folio); > > > > > > if (!folio_test_private(folio)) > > > return NULL; > > > folio_clear_private(folio); > > > folio->private = NULL; > > > folio_put(folio); > > > > > > return data; > > > } > > > > > > Or am I missing something? > > > > Ah, I missed folio_test_private() tho, can we really expect get_page(), > > SetPagePrivate(), and set_page_private() is in pair with folio_detach_private()? > > I guess we are trying to maintain PagePrivate and page_private w/ > inner {set,clear}_page_private_* functions, if they are called in paired correctly, > we don't need to call folio_detach_private() additionally in .release_folio and > .invalid_folio, right? Otherwise there must be a bug. Agreed. > > In this patch, I use bug_on to instead folio_detach_private(). > https://lore.kernel.org/linux-f2fs-devel/20230410022418.1843178-1-chao@xxxxxxxxxx/ > > In this patch, I use {attach,detach}_page_private() to clean up openned codes. > https://lore.kernel.org/linux-f2fs-devel/20230410022418.1843178-2-chao@xxxxxxxxxx/ Looks like it doesn't need to apply two patches, and missed f2fs_delete_entry case as well. >From 3fb0f570681dcd1c6c2f3e18ee7ff41428820b35 Mon Sep 17 00:00:00 2001 From: Chao Yu <chao@xxxxxxxxxx> Date: Mon, 10 Apr 2023 10:24:17 +0800 Subject: [PATCH] f2fs: remove folio_detach_private() in .invalidate_folio and .release_folio We have maintain PagePrivate and page_private and page reference w/ {set,clear}_page_private_*, it doesn't need to call folio_detach_private() in the end of .invalidate_folio and .release_folio, remove it and use f2fs_bug_on instead. Signed-off-by: Chao Yu <chao@xxxxxxxxxx> [Jaegeuk Kim: cover f2fs_delete_entry case] Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> --- fs/f2fs/data.c | 4 ++-- fs/f2fs/dir.c | 5 ++--- fs/f2fs/f2fs.h | 32 ++++++++------------------------ 3 files changed, 12 insertions(+), 29 deletions(-) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 5a3636b70f48..8870ff630409 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -3734,7 +3734,7 @@ void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length) inode->i_ino == F2FS_COMPRESS_INO(sbi)) clear_page_private_data(&folio->page); - folio_detach_private(folio); + f2fs_bug_on(sbi, page_private(&folio->page)); } bool f2fs_release_folio(struct folio *folio, gfp_t wait) @@ -3756,7 +3756,7 @@ bool f2fs_release_folio(struct folio *folio, gfp_t wait) clear_page_private_reference(&folio->page); clear_page_private_gcing(&folio->page); - folio_detach_private(folio); + f2fs_bug_on(sbi, page_private(&folio->page)); return true; } diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index d6dd8327e82d..cea179dec3b6 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -906,13 +906,12 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page, clear_page_dirty_for_io(page); ClearPageUptodate(page); + clear_page_private_reference(page); clear_page_private_gcing(page); + f2fs_bug_on(F2FS_I_SB(dir), page_private(page)); inode_dec_dirty_pages(dir); f2fs_remove_dirty_inode(dir); - - detach_page_private(page); - set_page_private(page, 0); } f2fs_put_page(page, 1); diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 68eadc1ac130..1b1df9e33028 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -1408,11 +1408,8 @@ static inline bool page_private_##name(struct page *page) \ #define PAGE_PRIVATE_SET_FUNC(name, flagname) \ static inline void set_page_private_##name(struct page *page) \ { \ - if (!PagePrivate(page)) { \ - get_page(page); \ - SetPagePrivate(page); \ - set_page_private(page, 0); \ - } \ + if (!PagePrivate(page)) \ + attach_page_private(page, (void *)0); \ set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); \ set_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \ } @@ -1421,13 +1418,8 @@ static inline void set_page_private_##name(struct page *page) \ static inline void clear_page_private_##name(struct page *page) \ { \ clear_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \ - if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) { \ - set_page_private(page, 0); \ - if (PagePrivate(page)) { \ - ClearPagePrivate(page); \ - put_page(page); \ - }\ - } \ + if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) \ + detach_page_private(page); \ } PAGE_PRIVATE_GET_FUNC(nonpointer, NOT_POINTER); @@ -1456,11 +1448,8 @@ static inline unsigned long get_page_private_data(struct page *page) static inline void set_page_private_data(struct page *page, unsigned long data) { - if (!PagePrivate(page)) { - get_page(page); - SetPagePrivate(page); - set_page_private(page, 0); - } + if (!PagePrivate(page)) + attach_page_private(page, (void *)0); set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); page_private(page) |= data << PAGE_PRIVATE_MAX; } @@ -1468,13 +1457,8 @@ static inline void set_page_private_data(struct page *page, unsigned long data) static inline void clear_page_private_data(struct page *page) { page_private(page) &= GENMASK(PAGE_PRIVATE_MAX - 1, 0); - if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) { - set_page_private(page, 0); - if (PagePrivate(page)) { - ClearPagePrivate(page); - put_page(page); - } - } + if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) + detach_page_private(page); } /* For compression */ -- 2.40.0.577.gac1e443424-goog > > With above two patches, I didn't hit any panic or use-after-free issue when testing > xfstest until now. > > Thanks, > > > > I feel attach/detach_page_private would look better? > > > > > > > > Thanks, > > > > > > > 1429 put_page(page); \ > > > > 1430 }\ > > > > 1431 } \ > > > > 1432 } > > > > > > > > > page is now free, gets reallocated into a THP > > > > > lookup from the f2fs file finds the new THP > > > > > things explode messily > > > > > > > > > > Checking page->mapping is going to avoid the messy explosion, but > > > > > you'll still have a page in the page cache which doesn't actually > > > > > belong to you, and that's going to lead to subtle data corruption. > > > > > > > > > > This should be caught by page_expected_state(), called from > > > > > free_page_is_bad(), called from free_pages_prepare(). Do your testers > > > > > have CONFIG_DEBUG_VM enabled? That might give you a fighting chance at > > > > > finding the last place which called put_page(). It won't necessarily be > > > > > the _wrong_ place to call put_page() (that may have happened earlier), > > > > > but it may give you a clue. > > > > > > > > > > > > > > > > > > > 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); > > > > > > > > }
