On 2018/5/8 11:31, Jaegeuk Kim wrote: > On 05/08, Chao Yu wrote: >> On 2018/5/8 4:46, Jaegeuk Kim wrote: >>> On 04/27, Chao Yu wrote: >>>> On 2018/4/27 0:36, Jaegeuk Kim wrote: >>>>> On 04/26, Chao Yu wrote: >>>>>> On 2018/4/26 23:48, Jaegeuk Kim wrote: >>>>>>> On 04/26, Chao Yu wrote: >>>>>>>> Thread A Thread B >>>>>>>> - f2fs_ioc_commit_atomic_write >>>>>>>> - commit_inmem_pages >>>>>>>> - f2fs_submit_merged_write_cond >>>>>>>> : write data >>>>>>>> - write_checkpoint >>>>>>>> - do_checkpoint >>>>>>>> : commit all node within CP >>>>>>>> -> SPO >>>>>>>> - f2fs_do_sync_file >>>>>>>> - file_write_and_wait_range >>>>>>>> : wait data writeback >>>>>>>> >>>>>>>> In above race condition, data/node can be flushed in reversed order >>>>>>>> when >>>>>>>> coming a checkpoint before f2fs_do_sync_file, after SPOR, it results in >>>>>>>> atomic written data being corrupted. >>>>>>> >>>>>>> Wait, what is the problem here? Thread B could succeed checkpoint, >>>>>>> there is >>>>>>> no problem. If it fails, there is no fsync mark where we can recover >>>>>>> it, so >>>>>> >>>>>> Node is flushed by checkpoint before data, with reversed order, that's >>>>>> the problem. >>>>> >>>>> What do you mean? Data should be in disk, in order to proceed checkpoint. >>>> >>>> 1. thread A: commit_inmem_pages submit data into block layer, but haven't >>>> waited >>>> it writeback. >>>> 2. thread A: commit_inmem_pages update related node. >>>> 3. thread B: do checkpoint, flush all nodes to disk >>> >>> How about, in block_operations(), >>> >>> down_read_trylock(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>> if (fail) >>> wait_on_all_pages_writeback(F2FS_WB_DATA); >>> else >>> up_read(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> >> I sent one patch for that, could you check it? >> >> Adding wait_on_all_pages_writeback in block_operations() can make >> checkpoint() >> wait pages writeback one more time, which break IO flow, so what's your >> concern >> here? > > Performance. And I can see wait_on_all_pages_writeback() waits only for > F2FS_WB_CP_DATA in checkpoint()?
Oh, you mean wait all F2FS_WB_DATA pages writeback, what about just treating atomic write page as F2FS_WB_CP_DATA, and we can wait atomic pages in wait_on_all_pages_writeback() in do_checkpoitn(). Thanks, > > >> >> Thanks, >> >>> >>> >>>> 4. SPOR >>>> >>>> Then, atomic file becomes corrupted since nodes is flushed before data. >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> Thanks, >>>>>> >>>>>>> we can just ignore the last written data as nothing. >>>>>>> >>>>>>>> >>>>>>>> This patch adds f2fs_wait_on_page_writeback in __revoke_inmem_pages() >>>>>>>> to >>>>>>>> keep data and node of atomic file being flushed orderly. >>>>>>>> >>>>>>>> Signed-off-by: Chao Yu <[email protected]> >>>>>>>> --- >>>>>>>> fs/f2fs/file.c | 4 ++++ >>>>>>>> fs/f2fs/segment.c | 3 +++ >>>>>>>> 2 files changed, 7 insertions(+) >>>>>>>> >>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>>>>> index be7578774a47..a352804af244 100644 >>>>>>>> --- a/fs/f2fs/file.c >>>>>>>> +++ b/fs/f2fs/file.c >>>>>>>> @@ -217,6 +217,9 @@ static int f2fs_do_sync_file(struct file *file, >>>>>>>> loff_t start, loff_t end, >>>>>>>> >>>>>>>> trace_f2fs_sync_file_enter(inode); >>>>>>>> >>>>>>>> + if (atomic) >>>>>>>> + goto write_done; >>>>>>>> + >>>>>>>> /* if fdatasync is triggered, let's do in-place-update */ >>>>>>>> if (datasync || get_dirty_pages(inode) <= >>>>>>>> SM_I(sbi)->min_fsync_blocks) >>>>>>>> set_inode_flag(inode, FI_NEED_IPU); >>>>>>>> @@ -228,6 +231,7 @@ static int f2fs_do_sync_file(struct file *file, >>>>>>>> loff_t start, loff_t end, >>>>>>>> return ret; >>>>>>>> } >>>>>>>> >>>>>>>> +write_done: >>>>>>>> /* if the inode is dirty, let's recover all the time */ >>>>>>>> if (!f2fs_skip_inode_update(inode, datasync)) { >>>>>>>> f2fs_write_inode(inode, NULL); >>>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>>>>>>> index 584483426584..9ca3d0a43d93 100644 >>>>>>>> --- a/fs/f2fs/segment.c >>>>>>>> +++ b/fs/f2fs/segment.c >>>>>>>> @@ -230,6 +230,8 @@ static int __revoke_inmem_pages(struct inode >>>>>>>> *inode, >>>>>>>> >>>>>>>> lock_page(page); >>>>>>>> >>>>>>>> + f2fs_wait_on_page_writeback(page, DATA, true); >>>>>>>> + >>>>>>>> if (recover) { >>>>>>>> struct dnode_of_data dn; >>>>>>>> struct node_info ni; >>>>>>>> @@ -415,6 +417,7 @@ static int __commit_inmem_pages(struct inode >>>>>>>> *inode) >>>>>>>> /* drop all uncommitted pages */ >>>>>>>> __revoke_inmem_pages(inode, &fi->inmem_pages, true, >>>>>>>> false); >>>>>>>> } else { >>>>>>>> + /* wait all committed IOs writeback and release them >>>>>>>> from list */ >>>>>>>> __revoke_inmem_pages(inode, &revoke_list, false, false); >>>>>>>> } >>>>>>>> >>>>>>>> -- >>>>>>>> 2.15.0.55.gc2ece9dc4de6 >>>>> >>>>> . >>>>> >>> >>> . >>> > > . > ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
