* [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-26 10:45 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-26 10:45 UTC (permalink / raw) To: jaegeuk; +Cc: linux-f2fs-devel, linux-kernel, chao, Chao Yu Thread A Background GC - f2fs_zero_range - truncate_pagecache_range - gc_data_segment - get_read_data_page - move_data_page - set_page_dirty - set_cold_data - f2fs_do_zero_range - dn->data_blkaddr = NEW_ADDR; - f2fs_set_data_blkaddr Actually, we don't need to set dirty & checked flag on the page, since all valid data in the page should be zeroed by zero_range(). Use i_gc_rwsem[WRITE] to avoid such race condition. Signed-off-by: Chao Yu <yuchao0@huawei.com> --- fs/f2fs/file.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 267ec3794e1e..7bd2412a8c37 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, if (ret) return ret; + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); down_write(&F2FS_I(inode)->i_mmap_sem); ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); if (ret) @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, } out_sem: up_write(&F2FS_I(inode)->i_mmap_sem); + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); return ret; } -- 2.18.0.rc1 ^ permalink raw reply related [flat|nested] 15+ messages in thread
* [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-26 10:45 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-26 10:45 UTC (permalink / raw) To: jaegeuk; +Cc: linux-f2fs-devel, linux-kernel, chao, Chao Yu Thread A Background GC - f2fs_zero_range - truncate_pagecache_range - gc_data_segment - get_read_data_page - move_data_page - set_page_dirty - set_cold_data - f2fs_do_zero_range - dn->data_blkaddr = NEW_ADDR; - f2fs_set_data_blkaddr Actually, we don't need to set dirty & checked flag on the page, since all valid data in the page should be zeroed by zero_range(). Use i_gc_rwsem[WRITE] to avoid such race condition. Signed-off-by: Chao Yu <yuchao0@huawei.com> --- fs/f2fs/file.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 267ec3794e1e..7bd2412a8c37 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, if (ret) return ret; + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); down_write(&F2FS_I(inode)->i_mmap_sem); ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); if (ret) @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, } out_sem: up_write(&F2FS_I(inode)->i_mmap_sem); + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); return ret; } -- 2.18.0.rc1 ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-26 10:45 ` Chao Yu (?) @ 2018-07-27 10:29 ` Jaegeuk Kim 2018-07-27 12:16 ` Chao Yu -1 siblings, 1 reply; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-27 10:29 UTC (permalink / raw) To: Chao Yu; +Cc: linux-f2fs-devel, linux-kernel, chao On 07/26, Chao Yu wrote: > Thread A Background GC > - f2fs_zero_range > - truncate_pagecache_range > - gc_data_segment > - get_read_data_page > - move_data_page > - set_page_dirty > - set_cold_data > - f2fs_do_zero_range > - dn->data_blkaddr = NEW_ADDR; > - f2fs_set_data_blkaddr > > Actually, we don't need to set dirty & checked flag on the page, since > all valid data in the page should be zeroed by zero_range(). But, it doesn't matter too much, right? > Use i_gc_rwsem[WRITE] to avoid such race condition. Hope to avoid abusing i_gc_rwsem[] tho. > > Signed-off-by: Chao Yu <yuchao0@huawei.com> > --- > fs/f2fs/file.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 267ec3794e1e..7bd2412a8c37 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > if (ret) > return ret; > > + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > down_write(&F2FS_I(inode)->i_mmap_sem); > ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > if (ret) > @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > } > out_sem: > up_write(&F2FS_I(inode)->i_mmap_sem); > + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > return ret; > } > -- > 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-27 10:29 ` Jaegeuk Kim @ 2018-07-27 12:16 ` Chao Yu 2018-07-29 2:02 ` Jaegeuk Kim 0 siblings, 1 reply; 15+ messages in thread From: Chao Yu @ 2018-07-27 12:16 UTC (permalink / raw) To: Jaegeuk Kim, Chao Yu; +Cc: linux-f2fs-devel, linux-kernel On 2018/7/27 18:29, Jaegeuk Kim wrote: > On 07/26, Chao Yu wrote: >> Thread A Background GC >> - f2fs_zero_range >> - truncate_pagecache_range >> - gc_data_segment >> - get_read_data_page >> - move_data_page >> - set_page_dirty >> - set_cold_data >> - f2fs_do_zero_range >> - dn->data_blkaddr = NEW_ADDR; >> - f2fs_set_data_blkaddr >> >> Actually, we don't need to set dirty & checked flag on the page, since >> all valid data in the page should be zeroed by zero_range(). > > But, it doesn't matter too much, right? No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of zero_range() should be wrong, as zeroed page contains valid user data. > >> Use i_gc_rwsem[WRITE] to avoid such race condition. > > Hope to avoid abusing i_gc_rwsem[] tho. Agreed, let's try avoiding until we have to use it. Thanks, > >> >> Signed-off-by: Chao Yu <yuchao0@huawei.com> >> --- >> fs/f2fs/file.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 267ec3794e1e..7bd2412a8c37 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >> if (ret) >> return ret; >> >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> down_write(&F2FS_I(inode)->i_mmap_sem); >> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >> if (ret) >> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >> } >> out_sem: >> up_write(&F2FS_I(inode)->i_mmap_sem); >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> >> return ret; >> } >> -- >> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-27 12:16 ` Chao Yu @ 2018-07-29 2:02 ` Jaegeuk Kim 0 siblings, 0 replies; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-29 2:02 UTC (permalink / raw) To: Chao Yu; +Cc: Chao Yu, linux-f2fs-devel, linux-kernel On 07/27, Chao Yu wrote: > On 2018/7/27 18:29, Jaegeuk Kim wrote: > > On 07/26, Chao Yu wrote: > >> Thread A Background GC > >> - f2fs_zero_range > >> - truncate_pagecache_range > >> - gc_data_segment > >> - get_read_data_page > >> - move_data_page > >> - set_page_dirty > >> - set_cold_data > >> - f2fs_do_zero_range > >> - dn->data_blkaddr = NEW_ADDR; > >> - f2fs_set_data_blkaddr > >> > >> Actually, we don't need to set dirty & checked flag on the page, since > >> all valid data in the page should be zeroed by zero_range(). > > > > But, it doesn't matter too much, right? > > No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > zero_range() should be wrong, as zeroed page contains valid user data. How about truncating page caches after block address change or doing it twice before and after? > > > > >> Use i_gc_rwsem[WRITE] to avoid such race condition. > > > > Hope to avoid abusing i_gc_rwsem[] tho. > > Agreed, let's try avoiding until we have to use it. > > Thanks, > > > > >> > >> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >> --- > >> fs/f2fs/file.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >> index 267ec3794e1e..7bd2412a8c37 100644 > >> --- a/fs/f2fs/file.c > >> +++ b/fs/f2fs/file.c > >> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >> if (ret) > >> return ret; > >> > >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >> down_write(&F2FS_I(inode)->i_mmap_sem); > >> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > >> if (ret) > >> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >> } > >> out_sem: > >> up_write(&F2FS_I(inode)->i_mmap_sem); > >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >> > >> return ret; > >> } > >> -- > >> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-29 2:02 ` Jaegeuk Kim 0 siblings, 0 replies; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-29 2:02 UTC (permalink / raw) To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel On 07/27, Chao Yu wrote: > On 2018/7/27 18:29, Jaegeuk Kim wrote: > > On 07/26, Chao Yu wrote: > >> Thread A Background GC > >> - f2fs_zero_range > >> - truncate_pagecache_range > >> - gc_data_segment > >> - get_read_data_page > >> - move_data_page > >> - set_page_dirty > >> - set_cold_data > >> - f2fs_do_zero_range > >> - dn->data_blkaddr = NEW_ADDR; > >> - f2fs_set_data_blkaddr > >> > >> Actually, we don't need to set dirty & checked flag on the page, since > >> all valid data in the page should be zeroed by zero_range(). > > > > But, it doesn't matter too much, right? > > No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > zero_range() should be wrong, as zeroed page contains valid user data. How about truncating page caches after block address change or doing it twice before and after? > > > > >> Use i_gc_rwsem[WRITE] to avoid such race condition. > > > > Hope to avoid abusing i_gc_rwsem[] tho. > > Agreed, let's try avoiding until we have to use it. > > Thanks, > > > > >> > >> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >> --- > >> fs/f2fs/file.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >> index 267ec3794e1e..7bd2412a8c37 100644 > >> --- a/fs/f2fs/file.c > >> +++ b/fs/f2fs/file.c > >> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >> if (ret) > >> return ret; > >> > >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >> down_write(&F2FS_I(inode)->i_mmap_sem); > >> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > >> if (ret) > >> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >> } > >> out_sem: > >> up_write(&F2FS_I(inode)->i_mmap_sem); > >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >> > >> return ret; > >> } > >> -- > >> 2.18.0.rc1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-29 2:02 ` Jaegeuk Kim (?) @ 2018-07-29 2:53 ` Chao Yu 2018-07-29 2:59 ` Jaegeuk Kim -1 siblings, 1 reply; 15+ messages in thread From: Chao Yu @ 2018-07-29 2:53 UTC (permalink / raw) To: Jaegeuk Kim; +Cc: Chao Yu, linux-f2fs-devel, linux-kernel On 2018/7/29 10:02, Jaegeuk Kim wrote: > On 07/27, Chao Yu wrote: >> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>> On 07/26, Chao Yu wrote: >>>> Thread A Background GC >>>> - f2fs_zero_range >>>> - truncate_pagecache_range >>>> - gc_data_segment >>>> - get_read_data_page >>>> - move_data_page >>>> - set_page_dirty >>>> - set_cold_data >>>> - f2fs_do_zero_range >>>> - dn->data_blkaddr = NEW_ADDR; >>>> - f2fs_set_data_blkaddr >>>> >>>> Actually, we don't need to set dirty & checked flag on the page, since >>>> all valid data in the page should be zeroed by zero_range(). >>> >>> But, it doesn't matter too much, right? >> >> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >> zero_range() should be wrong, as zeroed page contains valid user data. > > How about truncating page caches after block address change or doing it twice > before and after? Thread A Background GC - f2fs_zero_range - truncate_pagecache_range - gc_data_segment - get_read_data_page - move_data_page - set_page_dirty - set_cold_data - f2fs_do_zero_range - dn->data_blkaddr = NEW_ADDR; - f2fs_set_data_blkaddr bdi-flusher - __write_data_page - f2fs_update_data_blkaddr : data_blkaddr has been updated here. - truncate_pagecache_range : data & dnode has been writebacked before page cache truncation? How about this case? Thanks, > >> >>> >>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>> >>> Hope to avoid abusing i_gc_rwsem[] tho. >> >> Agreed, let's try avoiding until we have to use it. >> >> Thanks, >> >>> >>>> >>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>> --- >>>> fs/f2fs/file.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>> --- a/fs/f2fs/file.c >>>> +++ b/fs/f2fs/file.c >>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>> if (ret) >>>> return ret; >>>> >>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>> if (ret) >>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>> } >>>> out_sem: >>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>> >>>> return ret; >>>> } >>>> -- >>>> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-29 2:53 ` Chao Yu @ 2018-07-29 2:59 ` Jaegeuk Kim 2018-07-29 3:03 ` Chao Yu 0 siblings, 1 reply; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-29 2:59 UTC (permalink / raw) To: Chao Yu; +Cc: Chao Yu, linux-f2fs-devel, linux-kernel On 07/29, Chao Yu wrote: > On 2018/7/29 10:02, Jaegeuk Kim wrote: > > On 07/27, Chao Yu wrote: > >> On 2018/7/27 18:29, Jaegeuk Kim wrote: > >>> On 07/26, Chao Yu wrote: > >>>> Thread A Background GC > >>>> - f2fs_zero_range > >>>> - truncate_pagecache_range > >>>> - gc_data_segment > >>>> - get_read_data_page > >>>> - move_data_page > >>>> - set_page_dirty > >>>> - set_cold_data > >>>> - f2fs_do_zero_range > >>>> - dn->data_blkaddr = NEW_ADDR; > >>>> - f2fs_set_data_blkaddr > >>>> > >>>> Actually, we don't need to set dirty & checked flag on the page, since > >>>> all valid data in the page should be zeroed by zero_range(). > >>> > >>> But, it doesn't matter too much, right? > >> > >> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > >> zero_range() should be wrong, as zeroed page contains valid user data. > > > > How about truncating page caches after block address change or doing it twice > > before and after? > > Thread A Background GC > - f2fs_zero_range > - truncate_pagecache_range > - gc_data_segment > - get_read_data_page > - move_data_page > - set_page_dirty > - set_cold_data > - f2fs_do_zero_range > - dn->data_blkaddr = NEW_ADDR; > - f2fs_set_data_blkaddr > bdi-flusher > - __write_data_page > - f2fs_update_data_blkaddr > : data_blkaddr has been updated here. > - truncate_pagecache_range > : data & dnode has been writebacked before page cache truncation? > > How about this case? So, truncating pages under dnode lock can address it? > > Thanks, > > > > >> > >>> > >>>> Use i_gc_rwsem[WRITE] to avoid such race condition. > >>> > >>> Hope to avoid abusing i_gc_rwsem[] tho. > >> > >> Agreed, let's try avoiding until we have to use it. > >> > >> Thanks, > >> > >>> > >>>> > >>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >>>> --- > >>>> fs/f2fs/file.c | 2 ++ > >>>> 1 file changed, 2 insertions(+) > >>>> > >>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >>>> index 267ec3794e1e..7bd2412a8c37 100644 > >>>> --- a/fs/f2fs/file.c > >>>> +++ b/fs/f2fs/file.c > >>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>> if (ret) > >>>> return ret; > >>>> > >>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>> down_write(&F2FS_I(inode)->i_mmap_sem); > >>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > >>>> if (ret) > >>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>> } > >>>> out_sem: > >>>> up_write(&F2FS_I(inode)->i_mmap_sem); > >>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>> > >>>> return ret; > >>>> } > >>>> -- > >>>> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-29 2:59 ` Jaegeuk Kim @ 2018-07-29 3:03 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-29 3:03 UTC (permalink / raw) To: Jaegeuk Kim; +Cc: Chao Yu, linux-f2fs-devel, linux-kernel On 2018/7/29 10:59, Jaegeuk Kim wrote: > On 07/29, Chao Yu wrote: >> On 2018/7/29 10:02, Jaegeuk Kim wrote: >>> On 07/27, Chao Yu wrote: >>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>>>> On 07/26, Chao Yu wrote: >>>>>> Thread A Background GC >>>>>> - f2fs_zero_range >>>>>> - truncate_pagecache_range >>>>>> - gc_data_segment >>>>>> - get_read_data_page >>>>>> - move_data_page >>>>>> - set_page_dirty >>>>>> - set_cold_data >>>>>> - f2fs_do_zero_range >>>>>> - dn->data_blkaddr = NEW_ADDR; >>>>>> - f2fs_set_data_blkaddr >>>>>> >>>>>> Actually, we don't need to set dirty & checked flag on the page, since >>>>>> all valid data in the page should be zeroed by zero_range(). >>>>> >>>>> But, it doesn't matter too much, right? >>>> >>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >>>> zero_range() should be wrong, as zeroed page contains valid user data. >>> >>> How about truncating page caches after block address change or doing it twice >>> before and after? >> >> Thread A Background GC >> - f2fs_zero_range >> - truncate_pagecache_range >> - gc_data_segment >> - get_read_data_page >> - move_data_page >> - set_page_dirty >> - set_cold_data >> - f2fs_do_zero_range >> - dn->data_blkaddr = NEW_ADDR; >> - f2fs_set_data_blkaddr >> bdi-flusher >> - __write_data_page >> - f2fs_update_data_blkaddr >> : data_blkaddr has been updated here. >> - truncate_pagecache_range >> : data & dnode has been writebacked before page cache truncation? >> >> How about this case? > > So, truncating pages under dnode lock can address it? Normally, our lock dependency is ->writepage() lock data page -> lock dnode page here lock dnode page -> truncate_pagecache_range::lock data page Will easily cause deadlock? Thanks, > >> >> Thanks, >> >>> >>>> >>>>> >>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>>>> >>>>> Hope to avoid abusing i_gc_rwsem[] tho. >>>> >>>> Agreed, let's try avoiding until we have to use it. >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>>>> --- >>>>>> fs/f2fs/file.c | 2 ++ >>>>>> 1 file changed, 2 insertions(+) >>>>>> >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>>>> --- a/fs/f2fs/file.c >>>>>> +++ b/fs/f2fs/file.c >>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>> if (ret) >>>>>> return ret; >>>>>> >>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>>>> if (ret) >>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>> } >>>>>> out_sem: >>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>> >>>>>> return ret; >>>>>> } >>>>>> -- >>>>>> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-29 3:03 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-29 3:03 UTC (permalink / raw) To: Jaegeuk Kim; +Cc: linux-kernel, linux-f2fs-devel On 2018/7/29 10:59, Jaegeuk Kim wrote: > On 07/29, Chao Yu wrote: >> On 2018/7/29 10:02, Jaegeuk Kim wrote: >>> On 07/27, Chao Yu wrote: >>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>>>> On 07/26, Chao Yu wrote: >>>>>> Thread A Background GC >>>>>> - f2fs_zero_range >>>>>> - truncate_pagecache_range >>>>>> - gc_data_segment >>>>>> - get_read_data_page >>>>>> - move_data_page >>>>>> - set_page_dirty >>>>>> - set_cold_data >>>>>> - f2fs_do_zero_range >>>>>> - dn->data_blkaddr = NEW_ADDR; >>>>>> - f2fs_set_data_blkaddr >>>>>> >>>>>> Actually, we don't need to set dirty & checked flag on the page, since >>>>>> all valid data in the page should be zeroed by zero_range(). >>>>> >>>>> But, it doesn't matter too much, right? >>>> >>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >>>> zero_range() should be wrong, as zeroed page contains valid user data. >>> >>> How about truncating page caches after block address change or doing it twice >>> before and after? >> >> Thread A Background GC >> - f2fs_zero_range >> - truncate_pagecache_range >> - gc_data_segment >> - get_read_data_page >> - move_data_page >> - set_page_dirty >> - set_cold_data >> - f2fs_do_zero_range >> - dn->data_blkaddr = NEW_ADDR; >> - f2fs_set_data_blkaddr >> bdi-flusher >> - __write_data_page >> - f2fs_update_data_blkaddr >> : data_blkaddr has been updated here. >> - truncate_pagecache_range >> : data & dnode has been writebacked before page cache truncation? >> >> How about this case? > > So, truncating pages under dnode lock can address it? Normally, our lock dependency is ->writepage() lock data page -> lock dnode page here lock dnode page -> truncate_pagecache_range::lock data page Will easily cause deadlock? Thanks, > >> >> Thanks, >> >>> >>>> >>>>> >>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>>>> >>>>> Hope to avoid abusing i_gc_rwsem[] tho. >>>> >>>> Agreed, let's try avoiding until we have to use it. >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>>>> --- >>>>>> fs/f2fs/file.c | 2 ++ >>>>>> 1 file changed, 2 insertions(+) >>>>>> >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>>>> --- a/fs/f2fs/file.c >>>>>> +++ b/fs/f2fs/file.c >>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>> if (ret) >>>>>> return ret; >>>>>> >>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>>>> if (ret) >>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>> } >>>>>> out_sem: >>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>> >>>>>> return ret; >>>>>> } >>>>>> -- >>>>>> 2.18.0.rc1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-29 3:03 ` Chao Yu @ 2018-07-29 5:14 ` Jaegeuk Kim -1 siblings, 0 replies; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-29 5:14 UTC (permalink / raw) To: Chao Yu; +Cc: Chao Yu, linux-f2fs-devel, linux-kernel On 07/29, Chao Yu wrote: > On 2018/7/29 10:59, Jaegeuk Kim wrote: > > On 07/29, Chao Yu wrote: > >> On 2018/7/29 10:02, Jaegeuk Kim wrote: > >>> On 07/27, Chao Yu wrote: > >>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: > >>>>> On 07/26, Chao Yu wrote: > >>>>>> Thread A Background GC > >>>>>> - f2fs_zero_range > >>>>>> - truncate_pagecache_range > >>>>>> - gc_data_segment > >>>>>> - get_read_data_page > >>>>>> - move_data_page > >>>>>> - set_page_dirty > >>>>>> - set_cold_data > >>>>>> - f2fs_do_zero_range > >>>>>> - dn->data_blkaddr = NEW_ADDR; > >>>>>> - f2fs_set_data_blkaddr > >>>>>> > >>>>>> Actually, we don't need to set dirty & checked flag on the page, since > >>>>>> all valid data in the page should be zeroed by zero_range(). > >>>>> > >>>>> But, it doesn't matter too much, right? > >>>> > >>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > >>>> zero_range() should be wrong, as zeroed page contains valid user data. > >>> > >>> How about truncating page caches after block address change or doing it twice > >>> before and after? > >> > >> Thread A Background GC > >> - f2fs_zero_range > >> - truncate_pagecache_range > >> - gc_data_segment > >> - get_read_data_page > >> - move_data_page > >> - set_page_dirty > >> - set_cold_data > >> - f2fs_do_zero_range > >> - dn->data_blkaddr = NEW_ADDR; > >> - f2fs_set_data_blkaddr > >> bdi-flusher > >> - __write_data_page > >> - f2fs_update_data_blkaddr > >> : data_blkaddr has been updated here. > >> - truncate_pagecache_range > >> : data & dnode has been writebacked before page cache truncation? > >> > >> How about this case? > > > > So, truncating pages under dnode lock can address it? > > Normally, our lock dependency is > > ->writepage() > lock data page -> lock dnode page > > here > lock dnode page -> truncate_pagecache_range::lock data page > > Will easily cause deadlock? Yeah. Can we add an inode flag to bypass GC in this case, then? > > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>>> > >>>>> > >>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. > >>>>> > >>>>> Hope to avoid abusing i_gc_rwsem[] tho. > >>>> > >>>> Agreed, let's try avoiding until we have to use it. > >>>> > >>>> Thanks, > >>>> > >>>>> > >>>>>> > >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >>>>>> --- > >>>>>> fs/f2fs/file.c | 2 ++ > >>>>>> 1 file changed, 2 insertions(+) > >>>>>> > >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >>>>>> index 267ec3794e1e..7bd2412a8c37 100644 > >>>>>> --- a/fs/f2fs/file.c > >>>>>> +++ b/fs/f2fs/file.c > >>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>>>> if (ret) > >>>>>> return ret; > >>>>>> > >>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); > >>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > >>>>>> if (ret) > >>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>>>> } > >>>>>> out_sem: > >>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); > >>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>>>> > >>>>>> return ret; > >>>>>> } > >>>>>> -- > >>>>>> 2.18.0.rc1 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-29 5:14 ` Jaegeuk Kim 0 siblings, 0 replies; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-29 5:14 UTC (permalink / raw) To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel On 07/29, Chao Yu wrote: > On 2018/7/29 10:59, Jaegeuk Kim wrote: > > On 07/29, Chao Yu wrote: > >> On 2018/7/29 10:02, Jaegeuk Kim wrote: > >>> On 07/27, Chao Yu wrote: > >>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: > >>>>> On 07/26, Chao Yu wrote: > >>>>>> Thread A Background GC > >>>>>> - f2fs_zero_range > >>>>>> - truncate_pagecache_range > >>>>>> - gc_data_segment > >>>>>> - get_read_data_page > >>>>>> - move_data_page > >>>>>> - set_page_dirty > >>>>>> - set_cold_data > >>>>>> - f2fs_do_zero_range > >>>>>> - dn->data_blkaddr = NEW_ADDR; > >>>>>> - f2fs_set_data_blkaddr > >>>>>> > >>>>>> Actually, we don't need to set dirty & checked flag on the page, since > >>>>>> all valid data in the page should be zeroed by zero_range(). > >>>>> > >>>>> But, it doesn't matter too much, right? > >>>> > >>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > >>>> zero_range() should be wrong, as zeroed page contains valid user data. > >>> > >>> How about truncating page caches after block address change or doing it twice > >>> before and after? > >> > >> Thread A Background GC > >> - f2fs_zero_range > >> - truncate_pagecache_range > >> - gc_data_segment > >> - get_read_data_page > >> - move_data_page > >> - set_page_dirty > >> - set_cold_data > >> - f2fs_do_zero_range > >> - dn->data_blkaddr = NEW_ADDR; > >> - f2fs_set_data_blkaddr > >> bdi-flusher > >> - __write_data_page > >> - f2fs_update_data_blkaddr > >> : data_blkaddr has been updated here. > >> - truncate_pagecache_range > >> : data & dnode has been writebacked before page cache truncation? > >> > >> How about this case? > > > > So, truncating pages under dnode lock can address it? > > Normally, our lock dependency is > > ->writepage() > lock data page -> lock dnode page > > here > lock dnode page -> truncate_pagecache_range::lock data page > > Will easily cause deadlock? Yeah. Can we add an inode flag to bypass GC in this case, then? > > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>>> > >>>>> > >>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. > >>>>> > >>>>> Hope to avoid abusing i_gc_rwsem[] tho. > >>>> > >>>> Agreed, let's try avoiding until we have to use it. > >>>> > >>>> Thanks, > >>>> > >>>>> > >>>>>> > >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >>>>>> --- > >>>>>> fs/f2fs/file.c | 2 ++ > >>>>>> 1 file changed, 2 insertions(+) > >>>>>> > >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >>>>>> index 267ec3794e1e..7bd2412a8c37 100644 > >>>>>> --- a/fs/f2fs/file.c > >>>>>> +++ b/fs/f2fs/file.c > >>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>>>> if (ret) > >>>>>> return ret; > >>>>>> > >>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); > >>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > >>>>>> if (ret) > >>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > >>>>>> } > >>>>>> out_sem: > >>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); > >>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>>>> > >>>>>> return ret; > >>>>>> } > >>>>>> -- > >>>>>> 2.18.0.rc1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-29 5:14 ` Jaegeuk Kim (?) @ 2018-07-30 1:38 ` Jaegeuk Kim 2018-07-30 1:55 ` Chao Yu -1 siblings, 1 reply; 15+ messages in thread From: Jaegeuk Kim @ 2018-07-30 1:38 UTC (permalink / raw) To: Chao Yu; +Cc: linux-kernel, linux-f2fs-devel On 07/28, Jaegeuk Kim wrote: > On 07/29, Chao Yu wrote: > > On 2018/7/29 10:59, Jaegeuk Kim wrote: > > > On 07/29, Chao Yu wrote: > > >> On 2018/7/29 10:02, Jaegeuk Kim wrote: > > >>> On 07/27, Chao Yu wrote: > > >>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: > > >>>>> On 07/26, Chao Yu wrote: > > >>>>>> Thread A Background GC > > >>>>>> - f2fs_zero_range > > >>>>>> - truncate_pagecache_range > > >>>>>> - gc_data_segment > > >>>>>> - get_read_data_page > > >>>>>> - move_data_page > > >>>>>> - set_page_dirty > > >>>>>> - set_cold_data > > >>>>>> - f2fs_do_zero_range > > >>>>>> - dn->data_blkaddr = NEW_ADDR; > > >>>>>> - f2fs_set_data_blkaddr > > >>>>>> > > >>>>>> Actually, we don't need to set dirty & checked flag on the page, since > > >>>>>> all valid data in the page should be zeroed by zero_range(). > > >>>>> > > >>>>> But, it doesn't matter too much, right? > > >>>> > > >>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of > > >>>> zero_range() should be wrong, as zeroed page contains valid user data. > > >>> > > >>> How about truncating page caches after block address change or doing it twice > > >>> before and after? > > >> > > >> Thread A Background GC > > >> - f2fs_zero_range > > >> - truncate_pagecache_range > > >> - gc_data_segment > > >> - get_read_data_page > > >> - move_data_page > > >> - set_page_dirty > > >> - set_cold_data > > >> - f2fs_do_zero_range > > >> - dn->data_blkaddr = NEW_ADDR; > > >> - f2fs_set_data_blkaddr > > >> bdi-flusher > > >> - __write_data_page > > >> - f2fs_update_data_blkaddr > > >> : data_blkaddr has been updated here. > > >> - truncate_pagecache_range > > >> : data & dnode has been writebacked before page cache truncation? > > >> > > >> How about this case? > > > > > > So, truncating pages under dnode lock can address it? > > > > Normally, our lock dependency is > > > > ->writepage() > > lock data page -> lock dnode page > > > > here > > lock dnode page -> truncate_pagecache_range::lock data page > > > > Will easily cause deadlock? > > Yeah. Can we add an inode flag to bypass GC in this case, then? Hmm, BTW, how about using i_gc_rwsem[WRITE] in a very narrow scope? for (index = pg_start; index < pg_end;) { f2fs_lock_op(); down_write(i_gc_rwsem[WRITE]); truncate_page_cache_range(index, index + 4k); f2fs_do_zero_range(&dn, index, end); up_write(i_gc_rwsem[WRITE]); f2fs_unlock_op(); f2fs_balance_fs(); } > > > > > Thanks, > > > > > > > >> > > >> Thanks, > > >> > > >>> > > >>>> > > >>>>> > > >>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. > > >>>>> > > >>>>> Hope to avoid abusing i_gc_rwsem[] tho. > > >>>> > > >>>> Agreed, let's try avoiding until we have to use it. > > >>>> > > >>>> Thanks, > > >>>> > > >>>>> > > >>>>>> > > >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> > > >>>>>> --- > > >>>>>> fs/f2fs/file.c | 2 ++ > > >>>>>> 1 file changed, 2 insertions(+) > > >>>>>> > > >>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > >>>>>> index 267ec3794e1e..7bd2412a8c37 100644 > > >>>>>> --- a/fs/f2fs/file.c > > >>>>>> +++ b/fs/f2fs/file.c > > >>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > > >>>>>> if (ret) > > >>>>>> return ret; > > >>>>>> > > >>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > >>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); > > >>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); > > >>>>>> if (ret) > > >>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, > > >>>>>> } > > >>>>>> out_sem: > > >>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); > > >>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > >>>>>> > > >>>>>> return ret; > > >>>>>> } > > >>>>>> -- > > >>>>>> 2.18.0.rc1 > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > 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] 15+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: avoid race between zero_range and background GC 2018-07-30 1:38 ` [f2fs-dev] " Jaegeuk Kim @ 2018-07-30 1:55 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-30 1:55 UTC (permalink / raw) To: Jaegeuk Kim, Chao Yu; +Cc: linux-kernel, linux-f2fs-devel On 2018/7/30 9:38, Jaegeuk Kim wrote: > On 07/28, Jaegeuk Kim wrote: >> On 07/29, Chao Yu wrote: >>> On 2018/7/29 10:59, Jaegeuk Kim wrote: >>>> On 07/29, Chao Yu wrote: >>>>> On 2018/7/29 10:02, Jaegeuk Kim wrote: >>>>>> On 07/27, Chao Yu wrote: >>>>>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>>>>>>> On 07/26, Chao Yu wrote: >>>>>>>>> Thread A Background GC >>>>>>>>> - f2fs_zero_range >>>>>>>>> - truncate_pagecache_range >>>>>>>>> - gc_data_segment >>>>>>>>> - get_read_data_page >>>>>>>>> - move_data_page >>>>>>>>> - set_page_dirty >>>>>>>>> - set_cold_data >>>>>>>>> - f2fs_do_zero_range >>>>>>>>> - dn->data_blkaddr = NEW_ADDR; >>>>>>>>> - f2fs_set_data_blkaddr >>>>>>>>> >>>>>>>>> Actually, we don't need to set dirty & checked flag on the page, since >>>>>>>>> all valid data in the page should be zeroed by zero_range(). >>>>>>>> >>>>>>>> But, it doesn't matter too much, right? >>>>>>> >>>>>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >>>>>>> zero_range() should be wrong, as zeroed page contains valid user data. >>>>>> >>>>>> How about truncating page caches after block address change or doing it twice >>>>>> before and after? >>>>> >>>>> Thread A Background GC >>>>> - f2fs_zero_range >>>>> - truncate_pagecache_range >>>>> - gc_data_segment >>>>> - get_read_data_page >>>>> - move_data_page >>>>> - set_page_dirty >>>>> - set_cold_data >>>>> - f2fs_do_zero_range >>>>> - dn->data_blkaddr = NEW_ADDR; >>>>> - f2fs_set_data_blkaddr >>>>> bdi-flusher >>>>> - __write_data_page >>>>> - f2fs_update_data_blkaddr >>>>> : data_blkaddr has been updated here. >>>>> - truncate_pagecache_range >>>>> : data & dnode has been writebacked before page cache truncation? >>>>> >>>>> How about this case? >>>> >>>> So, truncating pages under dnode lock can address it? >>> >>> Normally, our lock dependency is >>> >>> ->writepage() >>> lock data page -> lock dnode page >>> >>> here >>> lock dnode page -> truncate_pagecache_range::lock data page >>> >>> Will easily cause deadlock? >> >> Yeah. Can we add an inode flag to bypass GC in this case, then? > > Hmm, BTW, how about using i_gc_rwsem[WRITE] in a very narrow scope? Oh, I can see that you submitted a patch to change lock dependency to: f2fs_lock_op() -> down_write(i_gc_rwsem[WRITE]) At a glance, I haven't see any place can cause deadlock now. > > for (index = pg_start; index < pg_end;) { > f2fs_lock_op(); > down_write(i_gc_rwsem[WRITE]); > truncate_page_cache_range(index, index + 4k); > f2fs_do_zero_range(&dn, index, end); > up_write(i_gc_rwsem[WRITE]); > f2fs_unlock_op(); > f2fs_balance_fs(); > } Let me update the patch as you suggested. Thanks, > >> >>> >>> Thanks, >>> >>>> >>>>> >>>>> Thanks, >>>>> >>>>>> >>>>>>> >>>>>>>> >>>>>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>>>>>>> >>>>>>>> Hope to avoid abusing i_gc_rwsem[] tho. >>>>>>> >>>>>>> Agreed, let's try avoiding until we have to use it. >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>>>>>>> --- >>>>>>>>> fs/f2fs/file.c | 2 ++ >>>>>>>>> 1 file changed, 2 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>>>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>>>>>>> --- a/fs/f2fs/file.c >>>>>>>>> +++ b/fs/f2fs/file.c >>>>>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>>>>> if (ret) >>>>>>>>> return ret; >>>>>>>>> >>>>>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>>>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>>>>>>> if (ret) >>>>>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>>>>> } >>>>>>>>> out_sem: >>>>>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>>>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>>>>> >>>>>>>>> return ret; >>>>>>>>> } >>>>>>>>> -- >>>>>>>>> 2.18.0.rc1 >> >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot >> _______________________________________________ >> 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] 15+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: avoid race between zero_range and background GC @ 2018-07-30 1:55 ` Chao Yu 0 siblings, 0 replies; 15+ messages in thread From: Chao Yu @ 2018-07-30 1:55 UTC (permalink / raw) To: Jaegeuk Kim, Chao Yu; +Cc: linux-kernel, linux-f2fs-devel On 2018/7/30 9:38, Jaegeuk Kim wrote: > On 07/28, Jaegeuk Kim wrote: >> On 07/29, Chao Yu wrote: >>> On 2018/7/29 10:59, Jaegeuk Kim wrote: >>>> On 07/29, Chao Yu wrote: >>>>> On 2018/7/29 10:02, Jaegeuk Kim wrote: >>>>>> On 07/27, Chao Yu wrote: >>>>>>> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>>>>>>> On 07/26, Chao Yu wrote: >>>>>>>>> Thread A Background GC >>>>>>>>> - f2fs_zero_range >>>>>>>>> - truncate_pagecache_range >>>>>>>>> - gc_data_segment >>>>>>>>> - get_read_data_page >>>>>>>>> - move_data_page >>>>>>>>> - set_page_dirty >>>>>>>>> - set_cold_data >>>>>>>>> - f2fs_do_zero_range >>>>>>>>> - dn->data_blkaddr = NEW_ADDR; >>>>>>>>> - f2fs_set_data_blkaddr >>>>>>>>> >>>>>>>>> Actually, we don't need to set dirty & checked flag on the page, since >>>>>>>>> all valid data in the page should be zeroed by zero_range(). >>>>>>>> >>>>>>>> But, it doesn't matter too much, right? >>>>>>> >>>>>>> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >>>>>>> zero_range() should be wrong, as zeroed page contains valid user data. >>>>>> >>>>>> How about truncating page caches after block address change or doing it twice >>>>>> before and after? >>>>> >>>>> Thread A Background GC >>>>> - f2fs_zero_range >>>>> - truncate_pagecache_range >>>>> - gc_data_segment >>>>> - get_read_data_page >>>>> - move_data_page >>>>> - set_page_dirty >>>>> - set_cold_data >>>>> - f2fs_do_zero_range >>>>> - dn->data_blkaddr = NEW_ADDR; >>>>> - f2fs_set_data_blkaddr >>>>> bdi-flusher >>>>> - __write_data_page >>>>> - f2fs_update_data_blkaddr >>>>> : data_blkaddr has been updated here. >>>>> - truncate_pagecache_range >>>>> : data & dnode has been writebacked before page cache truncation? >>>>> >>>>> How about this case? >>>> >>>> So, truncating pages under dnode lock can address it? >>> >>> Normally, our lock dependency is >>> >>> ->writepage() >>> lock data page -> lock dnode page >>> >>> here >>> lock dnode page -> truncate_pagecache_range::lock data page >>> >>> Will easily cause deadlock? >> >> Yeah. Can we add an inode flag to bypass GC in this case, then? > > Hmm, BTW, how about using i_gc_rwsem[WRITE] in a very narrow scope? Oh, I can see that you submitted a patch to change lock dependency to: f2fs_lock_op() -> down_write(i_gc_rwsem[WRITE]) At a glance, I haven't see any place can cause deadlock now. > > for (index = pg_start; index < pg_end;) { > f2fs_lock_op(); > down_write(i_gc_rwsem[WRITE]); > truncate_page_cache_range(index, index + 4k); > f2fs_do_zero_range(&dn, index, end); > up_write(i_gc_rwsem[WRITE]); > f2fs_unlock_op(); > f2fs_balance_fs(); > } Let me update the patch as you suggested. Thanks, > >> >>> >>> Thanks, >>> >>>> >>>>> >>>>> Thanks, >>>>> >>>>>> >>>>>>> >>>>>>>> >>>>>>>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>>>>>>> >>>>>>>> Hope to avoid abusing i_gc_rwsem[] tho. >>>>>>> >>>>>>> Agreed, let's try avoiding until we have to use it. >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> >>>>>>>>> --- >>>>>>>>> fs/f2fs/file.c | 2 ++ >>>>>>>>> 1 file changed, 2 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>>>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>>>>>>> --- a/fs/f2fs/file.c >>>>>>>>> +++ b/fs/f2fs/file.c >>>>>>>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>>>>> if (ret) >>>>>>>>> return ret; >>>>>>>>> >>>>>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>>>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>>>>>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>>>>>>> if (ret) >>>>>>>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>>>>>>> } >>>>>>>>> out_sem: >>>>>>>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>>>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>>>>>>> >>>>>>>>> return ret; >>>>>>>>> } >>>>>>>>> -- >>>>>>>>> 2.18.0.rc1 >> >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot >> _______________________________________________ >> 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] 15+ messages in thread
end of thread, other threads:[~2018-07-30 1:55 UTC | newest] Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2018-07-26 10:45 [PATCH] f2fs: avoid race between zero_range and background GC Chao Yu 2018-07-26 10:45 ` Chao Yu 2018-07-27 10:29 ` Jaegeuk Kim 2018-07-27 12:16 ` Chao Yu 2018-07-29 2:02 ` Jaegeuk Kim 2018-07-29 2:02 ` Jaegeuk Kim 2018-07-29 2:53 ` Chao Yu 2018-07-29 2:59 ` Jaegeuk Kim 2018-07-29 3:03 ` Chao Yu 2018-07-29 3:03 ` Chao Yu 2018-07-29 5:14 ` Jaegeuk Kim 2018-07-29 5:14 ` Jaegeuk Kim 2018-07-30 1:38 ` [f2fs-dev] " Jaegeuk Kim 2018-07-30 1:55 ` Chao Yu 2018-07-30 1:55 ` Chao Yu
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