Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files

From: Jaegeuk Kim
Date: Tue Sep 10 2019 - 08:09:19 EST

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In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files"
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On 09/10, Chao Yu wrote:
> On 2019/9/10 19:58, Jaegeuk Kim wrote:
> > On 09/10, Chao Yu wrote:
> >> On 2019/9/9 22:34, Jaegeuk Kim wrote:
> >>> On 09/09, Chao Yu wrote:
> >>>> On 2019/9/9 16:38, Jaegeuk Kim wrote:
> >>>>> On 09/09, Chao Yu wrote:
> >>>>>> On 2019/9/9 16:21, Jaegeuk Kim wrote:
> >>>>>>> On 09/09, Chao Yu wrote:
> >>>>>>>> On 2019/9/9 16:01, Jaegeuk Kim wrote:
> >>>>>>>>> On 09/09, Chao Yu wrote:
> >>>>>>>>>> On 2019/9/9 15:30, Jaegeuk Kim wrote:
> >>>>>>>>>>> On 09/09, Chao Yu wrote:
> >>>>>>>>>>>> On 2019/9/9 9:25, Jaegeuk Kim wrote:
> >>>>>>>>>>>>> If committing atomic pages is failed when doing f2fs_do_sync_file(), we can
> >>>>>>>>>>>>> get commited pages but atomic_file being still set like:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> - inmem: 0, atomic IO: 4 (Max. 10), volatile IO: 0 (Max. 0)
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> If GC selects this block, we can get an infinite loop like this:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> >>>>>>>>>>>>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> >>>>>>>>>>>>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> >>>>>>>>>>>>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> >>>>>>>>>>>>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> >>>>>>>>>>>>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> >>>>>>>>>>>>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> >>>>>>>>>>>>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> In that moment, we can observe:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> [Before]
> >>>>>>>>>>>>> Try to move 5084219 blocks (BG: 384508)
> >>>>>>>>>>>>> - data blocks : 4962373 (274483)
> >>>>>>>>>>>>> - node blocks : 121846 (110025)
> >>>>>>>>>>>>> Skipped : atomic write 4534686 (10)
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> [After]
> >>>>>>>>>>>>> Try to move 5088973 blocks (BG: 384508)
> >>>>>>>>>>>>> - data blocks : 4967127 (274483)
> >>>>>>>>>>>>> - node blocks : 121846 (110025)
> >>>>>>>>>>>>> Skipped : atomic write 4539440 (10)
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> >>>>>>>>>>>>> ---
> >>>>>>>>>>>>> fs/f2fs/file.c | 10 +++++-----
> >>>>>>>>>>>>> 1 file changed, 5 insertions(+), 5 deletions(-)
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>>>>>>>>>>>> index 7ae2f3bd8c2f..68b6da734e5f 100644
> >>>>>>>>>>>>> --- a/fs/f2fs/file.c
> >>>>>>>>>>>>> +++ b/fs/f2fs/file.c
> >>>>>>>>>>>>> @@ -1997,11 +1997,11 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
> >>>>>>>>>>>>> goto err_out;
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true);
> >>>>>>>>>>>>> - if (!ret) {
> >>>>>>>>>>>>> - clear_inode_flag(inode, FI_ATOMIC_FILE);
> >>>>>>>>>>>>> - F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
> >>>>>>>>>>>>> - stat_dec_atomic_write(inode);
> >>>>>>>>>>>>> - }
> >>>>>>>>>>>>> +
> >>>>>>>>>>>>> + /* doesn't need to check error */
> >>>>>>>>>>>>> + clear_inode_flag(inode, FI_ATOMIC_FILE);
> >>>>>>>>>>>>> + F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
> >>>>>>>>>>>>> + stat_dec_atomic_write(inode);
> >>>>>>>>>>>>
> >>>>>>>>>>>> If there are still valid atomic write pages linked in .inmem_pages, it may cause
> >>>>>>>>>>>> memory leak when we just clear FI_ATOMIC_FILE flag.
> >>>>>>>>>>>
> >>>>>>>>>>> f2fs_commit_inmem_pages() should have flushed them.
> >>>>>>>>>>
> >>>>>>>>>> Oh, we failed to flush its nodes.
> >>>>>>>>>>
> >>>>>>>>>> However we won't clear such info if we failed to flush inmen pages, it looks
> >>>>>>>>>> inconsistent.
> >>>>>>>>>>
> >>>>>>>>>> Any interface needed to drop inmem pages or clear ATOMIC_FILE flag in that two
> >>>>>>>>>> error path? I'm not very clear how sqlite handle such error.
> >>>>>>>>>
> >>>>>>>>> f2fs_drop_inmem_pages() did that, but not in this case.
> >>>>>>>>
> >>>>>>>> What I mean is, for any error returned from atomic_commit() interface, should
> >>>>>>>> userspace application handle it with consistent way, like trigger
> >>>>>>>> f2fs_drop_inmem_pages(), so we don't need to handle it inside atomic_commit().
> >>>>>>>
> >>>>>>> f2fs_ioc_abort_volatile_write() will be triggered.
> >>>>>>
> >>>>>> If userspace can do this, we can get rid of this patch, or am I missing sth?
> >>>>>
> >>>>> We don't know when that will come. And, other threads are waiting for GC here.
> >>>>
> >>>> Yes, however, even atomic_write won't be called sometimes... that's why we add
> >>>> handling logic in f2fs_gc().
> >>>
> >>> We need to clean this up like:
> >>>
> >>> If committing atomic pages is failed when doing f2fs_do_sync_file(), we can
> >>> get commited pages but atomic_file being still set like:
> >>>
> >>> - inmem: 0, atomic IO: 4 (Max. 10), volatile IO: 0 (Max. 0)
> >>>
> >>> If GC selects this block, we can get an infinite loop like this:
> >>>
> >>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> >>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> >>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> >>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> >>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> >>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> >>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> >>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> >>>
> >>> In that moment, we can observe:
> >>>
> >>> [Before]
> >>> Try to move 5084219 blocks (BG: 384508)
> >>> - data blocks : 4962373 (274483)
> >>> - node blocks : 121846 (110025)
> >>> Skipped : atomic write 4534686 (10)
> >>>
> >>> [After]
> >>> Try to move 5088973 blocks (BG: 384508)
> >>> - data blocks : 4967127 (274483)
> >>> - node blocks : 121846 (110025)
> >>> Skipped : atomic write 4539440 (10)
> >>>
> >>> So, refactor atomic_write flow like this:
> >>> 1. start_atomic_write
> >>> - add inmem_list and set atomic_file
> >>>
> >>> 2. write()
> >>> - register it in inmem_pages
> >>>
> >>> 3. commit_atomic_write
> >>> - if no error, f2fs_drop_inmem_pages()
> >>> - f2fs_commit_inmme_pages() failed
> >>> : __revoked_inmem_pages() was done
> >>> - f2fs_do_sync_file failed
> >>> : abort_atomic_write later
> >>>
> >>> 4. abort_atomic_write
> >>> - f2fs_drop_inmem_pages
> >>>
> >>> 5. f2fs_drop_inmem_pages
> >>> - clear atomic_file
> >>> - remove inmem_list
> >>
> >> Looks good.
> >>
> >>>
> >>> Based on this change, when GC fails to move block in atomic_file,
> >>> f2fs_drop_inmem_pages_all() can call f2fs_drop_inmem_pages().
> >>>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> >>> ---
> >>> fs/f2fs/file.c | 17 +++++++++++------
> >>> fs/f2fs/segment.c | 24 +++++-------------------
> >>> 2 files changed, 16 insertions(+), 25 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>> index 10927a0b8df3..1f499ac13d9a 100644
> >>> --- a/fs/f2fs/file.c
> >>> +++ b/fs/f2fs/file.c
> >>> @@ -1830,6 +1830,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
> >>> {
> >>> struct inode *inode = file_inode(filp);
> >>> int ret;
> >>> + struct f2fs_inode_info *fi = F2FS_I(inode);
> >>>
> >>> if (!inode_owner_or_capable(inode))
> >>> return -EACCES;
> >>> @@ -1871,10 +1872,17 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
> >>> goto out;
> >>> }
> >>>
> >>> - set_inode_flag(inode, FI_ATOMIC_FILE);
> >>> clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> >>> up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >>>
> >>> + spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> >>> + if (list_empty(&fi->inmem_ilist))
> >>> + list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> >>> + spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> >>> +
> >>> + /* add inode in inmem_list first and set atomic_file */
> >>> + set_inode_flag(inode, FI_ATOMIC_FILE);
> >>
> >> Should call up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]) here? Then in f2fs_gc(),
> >> we can check FI_ATOMIC_FILE atomically under i_gc_rwsem.
> >
> > Yup.
> >
> > If committing atomic pages is failed when doing f2fs_do_sync_file(), we can
> > get commited pages but atomic_file being still set like:
> >
> > - inmem: 0, atomic IO: 4 (Max. 10), volatile IO: 0 (Max. 0)
> >
> > If GC selects this block, we can get an infinite loop like this:
> >
> > f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> > f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> > f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> > f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> > f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
> > f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
> > f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
> > f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
> >
> > In that moment, we can observe:
> >
> > [Before]
> > Try to move 5084219 blocks (BG: 384508)
> > - data blocks : 4962373 (274483)
> > - node blocks : 121846 (110025)
> > Skipped : atomic write 4534686 (10)
> >
> > [After]
> > Try to move 5088973 blocks (BG: 384508)
> > - data blocks : 4967127 (274483)
> > - node blocks : 121846 (110025)
> > Skipped : atomic write 4539440 (10)
> >
> > So, refactor atomic_write flow like this:
> > 1. start_atomic_write
> > - add inmem_list and set atomic_file
> >
> > 2. write()
> > - register it in inmem_pages
> >
> > 3. commit_atomic_write
> > - if no error, f2fs_drop_inmem_pages()
> > - f2fs_commit_inmme_pages() failed
> > : __revoked_inmem_pages() was done
> > - f2fs_do_sync_file failed
> > : abort_atomic_write later
> >
> > 4. abort_atomic_write
> > - f2fs_drop_inmem_pages
> >
> > 5. f2fs_drop_inmem_pages
> > - clear atomic_file
> > - remove inmem_list
> >
> > Based on this change, when GC fails to move block in atomic_file,
> > f2fs_drop_inmem_pages_all() can call f2fs_drop_inmem_pages().
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> > fs/f2fs/file.c | 15 ++++++++++-----
> > fs/f2fs/segment.c | 27 ++++++---------------------
> > 2 files changed, 16 insertions(+), 26 deletions(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 10927a0b8df3..fab6e4cf8f06 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -1829,6 +1829,8 @@ static int f2fs_ioc_getversion(struct file *filp, unsigned long arg)
> > static int f2fs_ioc_start_atomic_write(struct file *filp)
> > {
> > struct inode *inode = file_inode(filp);
> > + struct f2fs_inode_info *fi = F2FS_I(inode);
> > + struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > int ret;
> >
> > if (!inode_owner_or_capable(inode))
> > @@ -1871,6 +1873,12 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
> > goto out;
> > }
> >
> > + spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> > + if (list_empty(&fi->inmem_ilist))
> > + list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> > + spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> > +
> > + /* add inode in inmem_list first and set atomic_file */
> > set_inode_flag(inode, FI_ATOMIC_FILE);
> > clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> > up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> > @@ -1912,11 +1920,8 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
> > goto err_out;
> >
> > ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true);
> > - if (!ret) {
> > - clear_inode_flag(inode, FI_ATOMIC_FILE);
> > - F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
> > - stat_dec_atomic_write(inode);
> > - }
> > + if (!ret)
> > + f2fs_drop_inmem_pages(inode);
> > } else {
> > ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false);
> > }
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 18584d4c078a..66343f451d73 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -185,8 +185,6 @@ bool f2fs_need_SSR(struct f2fs_sb_info *sbi)
> >
> > void f2fs_register_inmem_page(struct inode *inode, struct page *page)
> > {
> > - struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > - struct f2fs_inode_info *fi = F2FS_I(inode);
> > struct inmem_pages *new;
> >
> > f2fs_trace_pid(page);
> > @@ -200,15 +198,9 @@ void f2fs_register_inmem_page(struct inode *inode, struct page *page)
> > INIT_LIST_HEAD(&new->list);
> >
> > /* increase reference count with clean state */
> > - mutex_lock(&fi->inmem_lock);
>
> The lock is used to protect F2FS_I(inode)->inmem_pages list... it should be kept?

Urg.. yup. I added.

>
> Thanks,
>
> > get_page(page);
> > - list_add_tail(&new->list, &fi->inmem_pages);
> > - spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> > - if (list_empty(&fi->inmem_ilist))
> > - list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> > - spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> > + list_add_tail(&new->list, &F2FS_I(inode)->inmem_pages);
> > inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
> > - mutex_unlock(&fi->inmem_lock);
> >
> > trace_f2fs_register_inmem_page(page, INMEM);
> > }
> > @@ -330,19 +322,17 @@ void f2fs_drop_inmem_pages(struct inode *inode)
> > mutex_lock(&fi->inmem_lock);
> > __revoke_inmem_pages(inode, &fi->inmem_pages,
> > true, false, true);
> > -
> > - if (list_empty(&fi->inmem_pages)) {
> > - spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> > - if (!list_empty(&fi->inmem_ilist))
> > - list_del_init(&fi->inmem_ilist);
> > - spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> > - }
> > mutex_unlock(&fi->inmem_lock);
> > }
> >
> > clear_inode_flag(inode, FI_ATOMIC_FILE);
> > fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
> > stat_dec_atomic_write(inode);
> > +
> > + spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> > + if (!list_empty(&fi->inmem_ilist))
> > + list_del_init(&fi->inmem_ilist);
> > + spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> > }
> >
> > void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
> > @@ -471,11 +461,6 @@ int f2fs_commit_inmem_pages(struct inode *inode)
> >
> > mutex_lock(&fi->inmem_lock);
> > err = __f2fs_commit_inmem_pages(inode);
> > -
> > - spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> > - if (!list_empty(&fi->inmem_ilist))
> > - list_del_init(&fi->inmem_ilist);
> > - spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> > mutex_unlock(&fi->inmem_lock);
> >
> > clear_inode_flag(inode, FI_ATOMIC_COMMIT);
> >

Next message: Michal Hocko: "Re: [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling"
Previous message: Ardelean, Alexandru: "Re: [PATCH v3 1/2] ethtool: implement Energy Detect Powerdown support via phy-tunable"
In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files"
Next in thread: Chao Yu: "Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files"
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