| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <3b98678e-70e9-4af9-3067-bcb2820364bc@kernel.org>
Date: Tue, 11 Apr 2023 16:49:01 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, stable@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH] f2fs: get out of a repeat loop when getting a
locked data page
On 2023/4/11 7:24, Jaegeuk Kim wrote:
> 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@...r.kernel.org>
>>>>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.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?
>>>>>>>
>>>>>>>>
>>>>>>>> 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@kernel.org/
>>
>> 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@kernel.org/
>
> Looks like it doesn't need to apply two patches,
Agreed,
> and missed f2fs_delete_entry case as well.
Good catch, I have another patch that only clean up set_page_private(),
but I guess your below implementation covers all cases, thanks! :)
Thanks,
>
> From 3fb0f570681dcd1c6c2f3e18ee7ff41428820b35 Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao@...nel.org>
> 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@...nel.org>
> [Jaegeuk Kim: cover f2fs_delete_entry case]
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
> 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 */
Powered by blists - more mailing lists