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 <yuch...@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 ------------------------------------------------------------------------------ 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