* [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() @ 2020-02-12 10:34 Sahitya Tummala 2020-02-14 2:26 ` Chao Yu 0 siblings, 1 reply; 4+ messages in thread From: Sahitya Tummala @ 2020-02-12 10:34 UTC (permalink / raw) To: Jaegeuk Kim, Chao Yu, linux-f2fs-devel; +Cc: linux-kernel There could be a scenario where f2fs_sync_meta_pages() will not ensure that all F2FS_DIRTY_META pages are submitted for IO. Thus, resulting in the below panic in do_checkpoint() - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && !f2fs_cp_error(sbi)); This can happen in a low-memory condition, where shrinker could also be doing the writepage operation (stack shown below) at the same time when checkpoint is running on another core. schedule down_write f2fs_submit_page_write -> by this time, this page in page cache is tagged as PAGECACHE_TAG_WRITEBACK and PAGECACHE_TAG_DIRTY is cleared, due to which f2fs_sync_meta_pages() cannot sync this page in do_checkpoint() path. f2fs_do_write_meta_page __f2fs_write_meta_page f2fs_write_meta_page shrink_page_list shrink_inactive_list shrink_node_memcg shrink_node kswapd Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> --- fs/f2fs/checkpoint.c | 16 ++++++++-------- fs/f2fs/f2fs.h | 2 +- fs/f2fs/super.c | 2 +- 3 files changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c index ffdaba0..2b651a3 100644 --- a/fs/f2fs/checkpoint.c +++ b/fs/f2fs/checkpoint.c @@ -1250,14 +1250,14 @@ static void unblock_operations(struct f2fs_sb_info *sbi) f2fs_unlock_all(sbi); } -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type) { DEFINE_WAIT(wait); for (;;) { prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE); - if (!get_pages(sbi, F2FS_WB_CP_DATA)) + if (!get_pages(sbi, type)) break; if (unlikely(f2fs_cp_error(sbi))) @@ -1384,8 +1384,8 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) /* Flush all the NAT/SIT pages */ f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && - !f2fs_cp_error(sbi)); + /* Wait for all dirty meta pages to be submitted for IO */ + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); /* * modify checkpoint @@ -1493,11 +1493,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) /* Here, we have one bio having CP pack except cp pack 2 page */ f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && - !f2fs_cp_error(sbi)); + /* Wait for all dirty meta pages to be submitted for IO */ + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); /* wait for previous submitted meta pages writeback */ - f2fs_wait_on_all_pages_writeback(sbi); + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); /* flush all device cache */ err = f2fs_flush_device_cache(sbi); @@ -1506,7 +1506,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) /* barrier and flush checkpoint cp pack 2 page if it can */ commit_checkpoint(sbi, ckpt, start_blk); - f2fs_wait_on_all_pages_writeback(sbi); + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); /* * invalidate intermediate page cache borrowed from meta inode diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 5a888a0..b0e0535 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -3196,7 +3196,7 @@ bool f2fs_is_dirty_device(struct f2fs_sb_info *sbi, nid_t ino, void f2fs_update_dirty_page(struct inode *inode, struct page *page); void f2fs_remove_dirty_inode(struct inode *inode); int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type); -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi); +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type); int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc); void f2fs_init_ino_entry_info(struct f2fs_sb_info *sbi); int __init f2fs_create_checkpoint_caches(void); diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 5111e1f..084633b 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -1105,7 +1105,7 @@ static void f2fs_put_super(struct super_block *sb) /* our cp_error case, we can wait for any writeback page */ f2fs_flush_merged_writes(sbi); - f2fs_wait_on_all_pages_writeback(sbi); + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); f2fs_bug_on(sbi, sbi->fsync_node_num); -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() 2020-02-12 10:34 [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() Sahitya Tummala @ 2020-02-14 2:26 ` Chao Yu [not found] ` <20200214035425.GA20234@codeaurora.org> 0 siblings, 1 reply; 4+ messages in thread From: Chao Yu @ 2020-02-14 2:26 UTC (permalink / raw) To: Sahitya Tummala, Jaegeuk Kim, linux-f2fs-devel; +Cc: linux-kernel Hi Sahitya, On 2020/2/12 18:34, Sahitya Tummala wrote: > There could be a scenario where f2fs_sync_meta_pages() will not > ensure that all F2FS_DIRTY_META pages are submitted for IO. Thus, > resulting in the below panic in do_checkpoint() - > > f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && > !f2fs_cp_error(sbi)); > > This can happen in a low-memory condition, where shrinker could > also be doing the writepage operation (stack shown below) > at the same time when checkpoint is running on another core. > > schedule > down_write > f2fs_submit_page_write -> by this time, this page in page cache is tagged > as PAGECACHE_TAG_WRITEBACK and PAGECACHE_TAG_DIRTY > is cleared, due to which f2fs_sync_meta_pages() > cannot sync this page in do_checkpoint() path. > f2fs_do_write_meta_page > __f2fs_write_meta_page > f2fs_write_meta_page > shrink_page_list > shrink_inactive_list > shrink_node_memcg > shrink_node > kswapd IMO, there may be one more simple fix here: - f2fs_do_write_meta_page(sbi, page, io_type); dec_page_count(sbi, F2FS_DIRTY_META); + f2fs_do_write_meta_page(sbi, page, io_type); If we can remove F2FS_DIRTY_META reference count before we clear PAGECACHE_TAG_DIRTY, we can avoid this race condition. - dec_page_count(sbi, F2FS_DIRTY_META); - f2fs_do_write_meta_page - set_page_writeback - __test_set_page_writeback - xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); Thoughts? > > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> > --- > fs/f2fs/checkpoint.c | 16 ++++++++-------- > fs/f2fs/f2fs.h | 2 +- > fs/f2fs/super.c | 2 +- > 3 files changed, 10 insertions(+), 10 deletions(-) > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > index ffdaba0..2b651a3 100644 > --- a/fs/f2fs/checkpoint.c > +++ b/fs/f2fs/checkpoint.c > @@ -1250,14 +1250,14 @@ static void unblock_operations(struct f2fs_sb_info *sbi) > f2fs_unlock_all(sbi); > } > > -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) > +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type) > { > DEFINE_WAIT(wait); > > for (;;) { > prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE); > > - if (!get_pages(sbi, F2FS_WB_CP_DATA)) > + if (!get_pages(sbi, type)) > break; > > if (unlikely(f2fs_cp_error(sbi))) > @@ -1384,8 +1384,8 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) > > /* Flush all the NAT/SIT pages */ > f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); > - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && > - !f2fs_cp_error(sbi)); > + /* Wait for all dirty meta pages to be submitted for IO */ > + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); I'm afraid calling f2fs_wait_on_all_pages() after we call f2fs_sync_meta_pages() is low efficient, as we only want to write out dirty meta pages instead of wait for writebacking them to device cache. Thanks, > > /* > * modify checkpoint > @@ -1493,11 +1493,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) > > /* Here, we have one bio having CP pack except cp pack 2 page */ > f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); > - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && > - !f2fs_cp_error(sbi)); > + /* Wait for all dirty meta pages to be submitted for IO */ > + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); > > /* wait for previous submitted meta pages writeback */ > - f2fs_wait_on_all_pages_writeback(sbi); > + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); > > /* flush all device cache */ > err = f2fs_flush_device_cache(sbi); > @@ -1506,7 +1506,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) > > /* barrier and flush checkpoint cp pack 2 page if it can */ > commit_checkpoint(sbi, ckpt, start_blk); > - f2fs_wait_on_all_pages_writeback(sbi); > + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); > > /* > * invalidate intermediate page cache borrowed from meta inode > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 5a888a0..b0e0535 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -3196,7 +3196,7 @@ bool f2fs_is_dirty_device(struct f2fs_sb_info *sbi, nid_t ino, > void f2fs_update_dirty_page(struct inode *inode, struct page *page); > void f2fs_remove_dirty_inode(struct inode *inode); > int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type); > -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi); > +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type); > int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc); > void f2fs_init_ino_entry_info(struct f2fs_sb_info *sbi); > int __init f2fs_create_checkpoint_caches(void); > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > index 5111e1f..084633b 100644 > --- a/fs/f2fs/super.c > +++ b/fs/f2fs/super.c > @@ -1105,7 +1105,7 @@ static void f2fs_put_super(struct super_block *sb) > /* our cp_error case, we can wait for any writeback page */ > f2fs_flush_merged_writes(sbi); > > - f2fs_wait_on_all_pages_writeback(sbi); > + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); > > f2fs_bug_on(sbi, sbi->fsync_node_num); > > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ^ permalink raw reply [flat|nested] 4+ messages in thread
[parent not found: <20200214035425.GA20234@codeaurora.org>]
* Re: [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() [not found] ` <20200214035425.GA20234@codeaurora.org> @ 2020-02-14 7:16 ` Chao Yu 2020-02-14 7:35 ` Chao Yu 0 siblings, 1 reply; 4+ messages in thread From: Chao Yu @ 2020-02-14 7:16 UTC (permalink / raw) To: Sahitya Tummala; +Cc: Jaegeuk Kim, linux-kernel, linux-f2fs-devel Hi Sahitya, On 2020/2/14 11:54, Sahitya Tummala wrote: > Hi Chao, > > On Fri, Feb 14, 2020 at 10:26:18AM +0800, Chao Yu wrote: >> Hi Sahitya, >> >> On 2020/2/12 18:34, Sahitya Tummala wrote: >>> There could be a scenario where f2fs_sync_meta_pages() will not >>> ensure that all F2FS_DIRTY_META pages are submitted for IO. Thus, >>> resulting in the below panic in do_checkpoint() - >>> >>> f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>> !f2fs_cp_error(sbi)); >>> >>> This can happen in a low-memory condition, where shrinker could >>> also be doing the writepage operation (stack shown below) >>> at the same time when checkpoint is running on another core. >>> >>> schedule >>> down_write >>> f2fs_submit_page_write -> by this time, this page in page cache is tagged >>> as PAGECACHE_TAG_WRITEBACK and PAGECACHE_TAG_DIRTY >>> is cleared, due to which f2fs_sync_meta_pages() >>> cannot sync this page in do_checkpoint() path. >>> f2fs_do_write_meta_page >>> __f2fs_write_meta_page >>> f2fs_write_meta_page >>> shrink_page_list >>> shrink_inactive_list >>> shrink_node_memcg >>> shrink_node >>> kswapd >> >> IMO, there may be one more simple fix here: >> >> - f2fs_do_write_meta_page(sbi, page, io_type); >> dec_page_count(sbi, F2FS_DIRTY_META); >> >> + f2fs_do_write_meta_page(sbi, page, io_type); >> >> If we can remove F2FS_DIRTY_META reference count before we clear >> PAGECACHE_TAG_DIRTY, we can avoid this race condition. >> >> - dec_page_count(sbi, F2FS_DIRTY_META); >> - f2fs_do_write_meta_page >> - set_page_writeback >> - __test_set_page_writeback >> - xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); >> >> Thoughts? > > I believe it will be a problem because let's say the shrinker path is > still in the below stack - > > f2fs_submit_page_write(); > ->down_write(&io->io_rwsem); > > Then, the current f2fs_wait_on_all_pages_writeback() will not wait for > that page as it is not yet tagged as F2FS_WB_CP_DATA. Hence, the checkpoint > may proceed without waiting for this meta page to be written to disk. Oh, you're right. It looks the race can happen for data/node pages? like in fsync() procedure. > >> >>> >>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> >>> --- >>> fs/f2fs/checkpoint.c | 16 ++++++++-------- >>> fs/f2fs/f2fs.h | 2 +- >>> fs/f2fs/super.c | 2 +- >>> 3 files changed, 10 insertions(+), 10 deletions(-) >>> >>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c >>> index ffdaba0..2b651a3 100644 >>> --- a/fs/f2fs/checkpoint.c >>> +++ b/fs/f2fs/checkpoint.c >>> @@ -1250,14 +1250,14 @@ static void unblock_operations(struct f2fs_sb_info *sbi) >>> f2fs_unlock_all(sbi); >>> } >>> >>> -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) >>> +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type) >>> { >>> DEFINE_WAIT(wait); >>> >>> for (;;) { >>> prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE); >>> >>> - if (!get_pages(sbi, F2FS_WB_CP_DATA)) >>> + if (!get_pages(sbi, type)) >>> break; >>> >>> if (unlikely(f2fs_cp_error(sbi))) >>> @@ -1384,8 +1384,8 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>> >>> /* Flush all the NAT/SIT pages */ >>> f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); >>> - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>> - !f2fs_cp_error(sbi)); >>> + /* Wait for all dirty meta pages to be submitted for IO */ >>> + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); >> >> I'm afraid calling f2fs_wait_on_all_pages() after we call >> f2fs_sync_meta_pages() is low efficient, as we only want to write out >> dirty meta pages instead of wait for writebacking them to device cache. >> > > I have modified the existing function f2fs_wait_on_all_pages_writeback() to > a generic one f2fs_wait_on_all_pages(), where it will wait according to the > requested type. In this case, it will only wait for dirty F2FS_DIRTY_META pages > but not for the writeback to device cache. Oh, I see, as last dirty reference count decreaser won't wake up waiter, we need to wait for timeout, right? Can we decrease timeout count, maybe HZ/50 as we did for congestion. io_schedule_timeout(5*HZ); Thanks, > > Thanks, > >> Thanks, >> >>> >>> /* >>> * modify checkpoint >>> @@ -1493,11 +1493,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>> >>> /* Here, we have one bio having CP pack except cp pack 2 page */ >>> f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); >>> - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>> - !f2fs_cp_error(sbi)); >>> + /* Wait for all dirty meta pages to be submitted for IO */ >>> + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); >>> >>> /* wait for previous submitted meta pages writeback */ >>> - f2fs_wait_on_all_pages_writeback(sbi); >>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>> >>> /* flush all device cache */ >>> err = f2fs_flush_device_cache(sbi); >>> @@ -1506,7 +1506,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>> >>> /* barrier and flush checkpoint cp pack 2 page if it can */ >>> commit_checkpoint(sbi, ckpt, start_blk); >>> - f2fs_wait_on_all_pages_writeback(sbi); >>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>> >>> /* >>> * invalidate intermediate page cache borrowed from meta inode >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>> index 5a888a0..b0e0535 100644 >>> --- a/fs/f2fs/f2fs.h >>> +++ b/fs/f2fs/f2fs.h >>> @@ -3196,7 +3196,7 @@ bool f2fs_is_dirty_device(struct f2fs_sb_info *sbi, nid_t ino, >>> void f2fs_update_dirty_page(struct inode *inode, struct page *page); >>> void f2fs_remove_dirty_inode(struct inode *inode); >>> int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type); >>> -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi); >>> +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type); >>> int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc); >>> void f2fs_init_ino_entry_info(struct f2fs_sb_info *sbi); >>> int __init f2fs_create_checkpoint_caches(void); >>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>> index 5111e1f..084633b 100644 >>> --- a/fs/f2fs/super.c >>> +++ b/fs/f2fs/super.c >>> @@ -1105,7 +1105,7 @@ static void f2fs_put_super(struct super_block *sb) >>> /* our cp_error case, we can wait for any writeback page */ >>> f2fs_flush_merged_writes(sbi); >>> >>> - f2fs_wait_on_all_pages_writeback(sbi); >>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>> >>> f2fs_bug_on(sbi, sbi->fsync_node_num); >>> >>> > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() 2020-02-14 7:16 ` Chao Yu @ 2020-02-14 7:35 ` Chao Yu 0 siblings, 0 replies; 4+ messages in thread From: Chao Yu @ 2020-02-14 7:35 UTC (permalink / raw) To: Sahitya Tummala; +Cc: Jaegeuk Kim, linux-kernel, linux-f2fs-devel On 2020/2/14 15:16, Chao Yu wrote: > Hi Sahitya, > > On 2020/2/14 11:54, Sahitya Tummala wrote: >> Hi Chao, >> >> On Fri, Feb 14, 2020 at 10:26:18AM +0800, Chao Yu wrote: >>> Hi Sahitya, >>> >>> On 2020/2/12 18:34, Sahitya Tummala wrote: >>>> There could be a scenario where f2fs_sync_meta_pages() will not >>>> ensure that all F2FS_DIRTY_META pages are submitted for IO. Thus, >>>> resulting in the below panic in do_checkpoint() - >>>> >>>> f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>>> !f2fs_cp_error(sbi)); >>>> >>>> This can happen in a low-memory condition, where shrinker could >>>> also be doing the writepage operation (stack shown below) >>>> at the same time when checkpoint is running on another core. >>>> >>>> schedule >>>> down_write >>>> f2fs_submit_page_write -> by this time, this page in page cache is tagged >>>> as PAGECACHE_TAG_WRITEBACK and PAGECACHE_TAG_DIRTY >>>> is cleared, due to which f2fs_sync_meta_pages() >>>> cannot sync this page in do_checkpoint() path. >>>> f2fs_do_write_meta_page >>>> __f2fs_write_meta_page >>>> f2fs_write_meta_page >>>> shrink_page_list >>>> shrink_inactive_list >>>> shrink_node_memcg >>>> shrink_node >>>> kswapd >>> >>> IMO, there may be one more simple fix here: >>> >>> - f2fs_do_write_meta_page(sbi, page, io_type); >>> dec_page_count(sbi, F2FS_DIRTY_META); >>> >>> + f2fs_do_write_meta_page(sbi, page, io_type); >>> >>> If we can remove F2FS_DIRTY_META reference count before we clear >>> PAGECACHE_TAG_DIRTY, we can avoid this race condition. >>> >>> - dec_page_count(sbi, F2FS_DIRTY_META); >>> - f2fs_do_write_meta_page >>> - set_page_writeback >>> - __test_set_page_writeback >>> - xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); >>> >>> Thoughts? >> >> I believe it will be a problem because let's say the shrinker path is >> still in the below stack - >> >> f2fs_submit_page_write(); >> ->down_write(&io->io_rwsem); >> >> Then, the current f2fs_wait_on_all_pages_writeback() will not wait for >> that page as it is not yet tagged as F2FS_WB_CP_DATA. Hence, the checkpoint >> may proceed without waiting for this meta page to be written to disk. > > Oh, you're right. > > It looks the race can happen for data/node pages? like in fsync() procedure. I mean something like this: - fsync() - shrink - f2fs_do_sync_file - __write_node_page - set_page_writeback(page#0) : remove DIRTY/TOWRITE flag - f2fs_fsync_node_pages : won't find page #0 as TOWRITE flag was removeD - f2fs_wait_on_node_pages_writeback : wont' wait page #0 writeback as it was not in fsync_node_list list. - f2fs_add_fsync_node_entry Thanks, > >> >>> >>>> >>>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> >>>> --- >>>> fs/f2fs/checkpoint.c | 16 ++++++++-------- >>>> fs/f2fs/f2fs.h | 2 +- >>>> fs/f2fs/super.c | 2 +- >>>> 3 files changed, 10 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c >>>> index ffdaba0..2b651a3 100644 >>>> --- a/fs/f2fs/checkpoint.c >>>> +++ b/fs/f2fs/checkpoint.c >>>> @@ -1250,14 +1250,14 @@ static void unblock_operations(struct f2fs_sb_info *sbi) >>>> f2fs_unlock_all(sbi); >>>> } >>>> >>>> -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) >>>> +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type) >>>> { >>>> DEFINE_WAIT(wait); >>>> >>>> for (;;) { >>>> prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE); >>>> >>>> - if (!get_pages(sbi, F2FS_WB_CP_DATA)) >>>> + if (!get_pages(sbi, type)) >>>> break; >>>> >>>> if (unlikely(f2fs_cp_error(sbi))) >>>> @@ -1384,8 +1384,8 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>>> >>>> /* Flush all the NAT/SIT pages */ >>>> f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); >>>> - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>>> - !f2fs_cp_error(sbi)); >>>> + /* Wait for all dirty meta pages to be submitted for IO */ >>>> + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); >>> >>> I'm afraid calling f2fs_wait_on_all_pages() after we call >>> f2fs_sync_meta_pages() is low efficient, as we only want to write out >>> dirty meta pages instead of wait for writebacking them to device cache. >>> >> >> I have modified the existing function f2fs_wait_on_all_pages_writeback() to >> a generic one f2fs_wait_on_all_pages(), where it will wait according to the >> requested type. In this case, it will only wait for dirty F2FS_DIRTY_META pages >> but not for the writeback to device cache. > > Oh, I see, as last dirty reference count decreaser won't wake up waiter, we need > to wait for timeout, right? Can we decrease timeout count, maybe HZ/50 as we did > for congestion. > > io_schedule_timeout(5*HZ); > > Thanks, > >> >> Thanks, >> >>> Thanks, >>> >>>> >>>> /* >>>> * modify checkpoint >>>> @@ -1493,11 +1493,11 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>>> >>>> /* Here, we have one bio having CP pack except cp pack 2 page */ >>>> f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO); >>>> - f2fs_bug_on(sbi, get_pages(sbi, F2FS_DIRTY_META) && >>>> - !f2fs_cp_error(sbi)); >>>> + /* Wait for all dirty meta pages to be submitted for IO */ >>>> + f2fs_wait_on_all_pages(sbi, F2FS_DIRTY_META); >>>> >>>> /* wait for previous submitted meta pages writeback */ >>>> - f2fs_wait_on_all_pages_writeback(sbi); >>>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>>> >>>> /* flush all device cache */ >>>> err = f2fs_flush_device_cache(sbi); >>>> @@ -1506,7 +1506,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc) >>>> >>>> /* barrier and flush checkpoint cp pack 2 page if it can */ >>>> commit_checkpoint(sbi, ckpt, start_blk); >>>> - f2fs_wait_on_all_pages_writeback(sbi); >>>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>>> >>>> /* >>>> * invalidate intermediate page cache borrowed from meta inode >>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>>> index 5a888a0..b0e0535 100644 >>>> --- a/fs/f2fs/f2fs.h >>>> +++ b/fs/f2fs/f2fs.h >>>> @@ -3196,7 +3196,7 @@ bool f2fs_is_dirty_device(struct f2fs_sb_info *sbi, nid_t ino, >>>> void f2fs_update_dirty_page(struct inode *inode, struct page *page); >>>> void f2fs_remove_dirty_inode(struct inode *inode); >>>> int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type); >>>> -void f2fs_wait_on_all_pages_writeback(struct f2fs_sb_info *sbi); >>>> +void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type); >>>> int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc); >>>> void f2fs_init_ino_entry_info(struct f2fs_sb_info *sbi); >>>> int __init f2fs_create_checkpoint_caches(void); >>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>>> index 5111e1f..084633b 100644 >>>> --- a/fs/f2fs/super.c >>>> +++ b/fs/f2fs/super.c >>>> @@ -1105,7 +1105,7 @@ static void f2fs_put_super(struct super_block *sb) >>>> /* our cp_error case, we can wait for any writeback page */ >>>> f2fs_flush_merged_writes(sbi); >>>> >>>> - f2fs_wait_on_all_pages_writeback(sbi); >>>> + f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA); >>>> >>>> f2fs_bug_on(sbi, sbi->fsync_node_num); >>>> >>>> >> > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > . > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-02-14 7:35 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-02-12 10:34 [f2fs-dev] [PATCH] f2fs: fix the panic in do_checkpoint() Sahitya Tummala
2020-02-14 2:26 ` Chao Yu
[not found] ` <20200214035425.GA20234@codeaurora.org>
2020-02-14 7:16 ` Chao Yu
2020-02-14 7:35 ` Chao Yu
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