On 2016/7/7 6:37, Jaegeuk Kim wrote: > On Wed, Jul 06, 2016 at 10:10:57AM +0800, Chao Yu wrote: >> On 2016/7/6 8:24, Jaegeuk Kim wrote: >>> On Fri, Jul 01, 2016 at 02:03:17PM +0800, Chao Yu wrote: >>>> Hi Jaegeuk, >>>> >>>> On 2016/7/1 8:03, Jaegeuk Kim wrote: >>>>> Hi Chao, >>>>> >>>>> On Thu, Jun 30, 2016 at 04:42:48PM +0800, Chao Yu wrote: >>>>>> Datas in file can be operated by GC and DIO simultaneously, so we will >>>>>> face race case as below: >>>>>> >>>>>> For write case: >>>>>> Thread A Thread B >>>>>> - generic_file_direct_write >>>>>> - invalidate_inode_pages2_range >>>>>> - f2fs_direct_IO >>>>>> - do_blockdev_direct_IO >>>>>> - do_direct_IO >>>>>> - get_more_blocks >>>>>> - f2fs_gc >>>>>> - do_garbage_collect >>>>>> - gc_data_segment >>>>>> - move_data_page >>>>>> - do_write_data_page >>>>>> migrate data block to new block >>>>>> address >>>>>> - dio_bio_submit >>>>>> update user data to old block address >>>>>> >>>>>> For read case: >>>>>> Thread A Thread B >>>>>> - generic_file_direct_write >>>>>> - invalidate_inode_pages2_range >>>>>> - f2fs_direct_IO >>>>>> - do_blockdev_direct_IO >>>>>> - do_direct_IO >>>>>> - get_more_blocks >>>>>> - f2fs_balance_fs >>>>>> - f2fs_gc >>>>>> - do_garbage_collect >>>>>> - gc_data_segment >>>>>> - move_data_page >>>>>> - do_write_data_page >>>>>> migrate data block to new block >>>>>> address >>>>>> - write_checkpoint >>>>>> - do_checkpoint >>>>>> - clear_prefree_segments >>>>>> - f2fs_issue_discard >>>>>> discard old block adress >>>>>> - dio_bio_submit >>>>>> update user buffer from obsolete block address >>>>>> >>>>>> In order to fix this, for one file, we should let DIO and GC getting >>>>>> exclusion >>>>>> against with each other. >>>>>> >>>>>> Signed-off-by: Chao Yu <yuch...@huawei.com> >>>>>> --- >>>>>> fs/f2fs/data.c | 2 ++ >>>>>> fs/f2fs/f2fs.h | 1 + >>>>>> fs/f2fs/gc.c | 14 +++++++++++++- >>>>>> fs/f2fs/super.c | 1 + >>>>>> 4 files changed, 17 insertions(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>>>> index ba4963f..08dc060 100644 >>>>>> --- a/fs/f2fs/data.c >>>>>> +++ b/fs/f2fs/data.c >>>>>> @@ -1716,7 +1716,9 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, >>>>>> struct iov_iter *iter) >>>>>> >>>>>> trace_f2fs_direct_IO_enter(inode, offset, count, >>>>>> iov_iter_rw(iter)); >>>>>> >>>>>> + mutex_lock(&F2FS_I(inode)->dio_mutex); >>>>>> err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio); >>>>>> + mutex_unlock(&F2FS_I(inode)->dio_mutex); >>>>> >>>>> This means we need to sacrifice entire parallism even in the normal cases? >>>>> Can we find another way? >>>> >>>> 1. For dio write vs dio write, writer will grab i_mutex before dio_mutex, >>>> so >>>> anyway, concurrent dio writes will be exclusive. >>>> >>>> 2. For dio write vs gc, keep using dio_mutex for making them exclusive. >>>> >>>> 3. For dio read vs dio read, and dio read vs gc, what about adding >>>> dio_rwsem to >>>> control the parallelism? >>>> >>>> 4. For dio write vs dio read, we grab different lock (write grabs >>>> dio_mutex, >>>> read grabs dio_rwsem), so there is no race condition. >>> >>> How about adding a flag in a dio inode and avoiding GCs for there-in blocks? >> >> Hmm.. IMO, without lock, it's hard to keep the sequence that let GC checking >> the >> flag after setting it, right? > > Okay, could you add dio_rwsem for now? > Later, we may need to take a look at dio_overwrite case to mitigate inode_lock > contention likewise xfs. :)
Sounds good if we can support concurrent overwrite dio! :) Let me send v3. Thanks, > > Thanks, > >>>>> >>>>>> if (iov_iter_rw(iter) == WRITE) { >>>>>> if (err > 0) >>>>>> set_inode_flag(inode, FI_UPDATE_WRITE); >>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>>>>> index bd82b6d..a241576 100644 >>>>>> --- a/fs/f2fs/f2fs.h >>>>>> +++ b/fs/f2fs/f2fs.h >>>>>> @@ -474,6 +474,7 @@ struct f2fs_inode_info { >>>>>> struct list_head inmem_pages; /* inmemory pages managed by >>>>>> f2fs */ >>>>>> struct mutex inmem_lock; /* lock for inmemory pages */ >>>>>> struct extent_tree *extent_tree; /* cached extent_tree >>>>>> entry */ >>>>>> + struct mutex dio_mutex; /* avoid racing between dio and >>>>>> gc */ >>>>>> }; >>>>>> >>>>>> static inline void get_extent_info(struct extent_info *ext, >>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>>> index c2c4ac3..98e3763 100644 >>>>>> --- a/fs/f2fs/gc.c >>>>>> +++ b/fs/f2fs/gc.c >>>>>> @@ -744,12 +744,24 @@ next_step: >>>>>> /* phase 3 */ >>>>>> inode = find_gc_inode(gc_list, dni.ino); >>>>>> if (inode) { >>>>>> + bool locked = false; >>>>>> + >>>>>> + if (S_ISREG(inode->i_mode)) { >>>>>> + if >>>>>> (!mutex_trylock(&F2FS_I(inode)->dio_mutex)) >>>>>> + continue; >>>>>> + locked = true; >>>>>> + } >>>>>> + >>>>>> start_bidx = start_bidx_of_node(nofs, inode) >>>>>> + >>>>>> ofs_in_node; >>>>>> - if (f2fs_encrypted_inode(inode) && >>>>>> S_ISREG(inode->i_mode)) >>>>>> + if (f2fs_encrypted_inode(inode) && >>>>>> + >>>>>> S_ISREG(inode->i_mode)) >>>>>> move_encrypted_block(inode, start_bidx); >>>>>> else >>>>>> move_data_page(inode, start_bidx, >>>>>> gc_type); >>>>>> + if (locked) >>>>>> + mutex_unlock(&F2FS_I(inode)->dio_mutex); >>>>>> + >>>>>> stat_inc_data_blk_count(sbi, 1, gc_type); >>>>>> } >>>>>> } >>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>>>>> index 8c698e1..24aab3f 100644 >>>>>> --- a/fs/f2fs/super.c >>>>>> +++ b/fs/f2fs/super.c >>>>>> @@ -575,6 +575,7 @@ static struct inode *f2fs_alloc_inode(struct >>>>>> super_block *sb) >>>>>> INIT_LIST_HEAD(&fi->gdirty_list); >>>>>> INIT_LIST_HEAD(&fi->inmem_pages); >>>>>> mutex_init(&fi->inmem_lock); >>>>>> + mutex_init(&fi->dio_mutex); >>>>>> >>>>>> /* Will be used by directory only */ >>>>>> fi->i_dir_level = F2FS_SB(sb)->dir_level; >>>>>> -- >>>>>> 2.8.2.311.gee88674 >>>>> >>>>> . >>>>> >>> >>> . >>> > > ------------------------------------------------------------------------------ > Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San > Francisco, CA to explore cutting-edge tech and listen to tech luminaries > present their vision of the future. This family event has something for > everyone, including kids. Get more information and register today. > http://sdm.link/attshape > _______________________________________________ > Linux-f2fs-devel mailing list > linux-f2fs-de...@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >