On 2018/2/5 14:40, Yunlong Song wrote: > Is it necessary to make atomic commit fail? What's the problem of this > patch (no lock at all and does not make atomic fail)? These two patches > aims to provide ability to gc old blocks of opened atomic file, with no > affection to original atomic commit and no mix with inmem pages. > > On 2018/2/5 14:29, Chao Yu wrote: >> On 2018/2/5 10:53, Yunlong Song wrote: >>> Is it necessary to add a lock here? What's the problem of this patch (no >>> lock at all)? Anyway, the problem is expected to be fixed asap, since >>> attackers can easily write an app with only atomic start and no atomic >>> commit, which will cause f2fs run into loop gc if the disk layout is >>> much fragmented, since f2fs_gc will select the same target victim all >>> the time (e.g. one block of target victim belongs to the opened atomic >>> file, and it will not be moved and do_garbage_collect will finally >>> return 0, and that victim is selected again next time) and goto gc_more >>> time and time again, which will block all the fs ops (all the fs ops >>> will hang up in f2fs_balance_fs). >> >> Hmm.. w/ original commit log and implementation, I supposed that the patch >> intended to fix to make atomic write be isolated from other IOs like GC >> triggered writes... >> >> Alright, we have discuss the problem before in below link: >> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1571951.html >> >> I meant, for example: >> >> f2fs_ioc_start_atomic_write() >> inode->atomic_open_time = get_mtime(); >> >> f2fs_ioc_commit_atomic_write() >> inode->atomic_open_time = 0; >> >> f2fs_balance_fs_bg() >> for_each_atomic_open_file() >> if (inode->atomic_open_time && >> inode->atomic_open_time > threshold) { >> drop_inmem_pages(); >> f2fs_msg(); >> } >> >> threshold = 30s >> >> Any thoughts? >> >> Thanks, >> >>> >>> On 2018/2/4 22:56, Chao Yu wrote: >>>> On 2018/2/3 10:47, Yunlong Song wrote: >>>>> If inode has already started to atomic commit, then set_page_dirty will >>>>> not mix the gc pages with the inmem atomic pages, so the page can be >>>>> gced safely. >>>> >>>> Let's avoid Ccing fs mailing list if the patch didn't change vfs common >>>> codes. >>>> >>>> As you know, the problem here is mixed dnode block flushing w/o >>>> writebacking >>>> gced data block, result in making transaction unintegrated.
OK, details as I explained before: atomic_commit GC - file_write_and_wait_range - move_data_block - f2fs_submit_page_write - f2fs_update_data_blkaddr - set_page_dirty - fsync_node_pages 1. atomic writes data page #1 & update node #1 2. GC data page #2 & update node #2 3. page #1 & node #1 & #2 can be committed into nand flash before page #2 be committed. After a sudden pow-cut, database transaction will be inconsistent. So I think there will be better to exclude gc/atomic_write to each other, with a lock instead of flag checking. Thanks, >>>> >>>> So how about just using dio_rwsem[WRITE] during atomic committing to >>>> exclude >>>> GCing data block of atomic opened file? >>>> >>>> Thanks, >>>> >>>>> >>>>> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com> >>>>> --- >>>>> fs/f2fs/data.c | 5 ++--- >>>>> fs/f2fs/gc.c | 6 ++++-- >>>>> 2 files changed, 6 insertions(+), 5 deletions(-) >>>>> >>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>>> index 7435830..edafcb6 100644 >>>>> --- a/fs/f2fs/data.c >>>>> +++ b/fs/f2fs/data.c >>>>> @@ -1580,14 +1580,13 @@ bool should_update_outplace(struct inode *inode, >>>>> struct f2fs_io_info *fio) >>>>> return true; >>>>> if (S_ISDIR(inode->i_mode)) >>>>> return true; >>>>> - if (f2fs_is_atomic_file(inode)) >>>>> - return true; >>>>> if (fio) { >>>>> if (is_cold_data(fio->page)) >>>>> return true; >>>>> if (IS_ATOMIC_WRITTEN_PAGE(fio->page)) >>>>> return true; >>>>> - } >>>>> + } else if (f2fs_is_atomic_file(inode)) >>>>> + return true; >>>>> return false; >>>>> } >>>>> >>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>> index b9d93fd..84ab3ff 100644 >>>>> --- a/fs/f2fs/gc.c >>>>> +++ b/fs/f2fs/gc.c >>>>> @@ -622,7 +622,8 @@ static void move_data_block(struct inode *inode, >>>>> block_t bidx, >>>>> if (!check_valid_map(F2FS_I_SB(inode), segno, off)) >>>>> goto out; >>>>> >>>>> - if (f2fs_is_atomic_file(inode)) >>>>> + if (f2fs_is_atomic_file(inode) && >>>>> + !f2fs_is_commit_atomic_write(inode)) >>>>> goto out; >>>>> >>>>> if (f2fs_is_pinned_file(inode)) { >>>>> @@ -729,7 +730,8 @@ static void move_data_page(struct inode *inode, >>>>> block_t bidx, int gc_type, >>>>> if (!check_valid_map(F2FS_I_SB(inode), segno, off)) >>>>> goto out; >>>>> >>>>> - if (f2fs_is_atomic_file(inode)) >>>>> + if (f2fs_is_atomic_file(inode) && >>>>> + !f2fs_is_commit_atomic_write(inode)) >>>>> goto out; >>>>> if (f2fs_is_pinned_file(inode)) { >>>>> if (gc_type == FG_GC) >>>>> >>>> >>>> . >>>> >>> >> >> >> . >> >