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 <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
