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From: Chao Yu <yuchao0@huawei.com>
To: Jaegeuk Kim <jaegeuk@kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-f2fs-devel@lists.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: avoid fi->i_gc_rwsem[WRITE] lock in f2fs_gc
Date: Thu, 9 Aug 2018 09:44:15 +0800
Message-ID: <16d7f719-268f-99f4-c5b2-fc893b557f11@huawei.com> (raw)
In-Reply-To: <20180805163450.GB55836@jaegeuk-macbookpro.roam.corp.google.com>

On 2018/8/6 0:34, Jaegeuk Kim wrote:
> The f2fs_gc() called by f2fs_balance_fs() requires to be called outside of
> fi->i_gc_rwsem[WRITE], since f2fs_gc() can try to grab it in a loop.
> 
> If it hits the miximum retrials in GC, let's give a chance to release
> gc_mutex for a short time in order not to go into live lock in the worst
> case.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  v3
>   - don't revoke atomic_writes all the time due to gc_rwsem
>   - keep lock order in f2fs_commit_inmem_pages
> 
>  fs/f2fs/f2fs.h    |  1 +
>  fs/f2fs/file.c    | 76 ++++++++++++++++++++++++-----------------------
>  fs/f2fs/gc.c      | 24 +++++++++++----
>  fs/f2fs/segment.c |  6 +++-
>  fs/f2fs/segment.h |  2 +-
>  5 files changed, 64 insertions(+), 45 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1647a13be7f9..0c65c3146ead 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1234,6 +1234,7 @@ struct f2fs_sb_info {
>  	unsigned int gc_mode;			/* current GC state */
>  	/* for skip statistic */
>  	unsigned long long skipped_atomic_files[2];	/* FG_GC and BG_GC */
> +	unsigned long long skipped_gc_rwsem;		/* FG_GC only */
>  
>  	/* threshold for gc trials on pinned files */
>  	u64 gc_pin_file_threshold;
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 67c9c2d4e2d9..4e2e3938f474 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1180,25 +1180,31 @@ static int __exchange_data_block(struct inode *src_inode,
>  	return ret;
>  }
>  
> -static int f2fs_do_collapse(struct inode *inode, pgoff_t start, pgoff_t end)
> +static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	pgoff_t nrpages = (i_size_read(inode) + PAGE_SIZE - 1) / PAGE_SIZE;
> +	pgoff_t start = offset >> PAGE_SHIFT;
> +	pgoff_t end = (offset + len) >> PAGE_SHIFT;
>  	int ret;
>  
>  	f2fs_balance_fs(sbi, true);
> -	f2fs_lock_op(sbi);
>  
> -	f2fs_drop_extent_tree(inode);
> +	/* avoid gc operation during block exchange */
> +	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  
> +	f2fs_lock_op(sbi);
> +	f2fs_drop_extent_tree(inode);
> +	truncate_pagecache(inode, offset);
>  	ret = __exchange_data_block(inode, inode, end, start, nrpages - end, true);
>  	f2fs_unlock_op(sbi);
> +
> +	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	return ret;
>  }
>  
>  static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
>  {
> -	pgoff_t pg_start, pg_end;
>  	loff_t new_size;
>  	int ret;
>  
> @@ -1213,21 +1219,13 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
>  	if (ret)
>  		return ret;
>  
> -	pg_start = offset >> PAGE_SHIFT;
> -	pg_end = (offset + len) >> PAGE_SHIFT;
> -
> -	/* avoid gc operation during block exchange */
> -	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> -
>  	down_write(&F2FS_I(inode)->i_mmap_sem);
>  	/* write out all dirty pages from offset */
>  	ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
>  	if (ret)
>  		goto out_unlock;
>  
> -	truncate_pagecache(inode, offset);
> -
> -	ret = f2fs_do_collapse(inode, pg_start, pg_end);
> +	ret = f2fs_do_collapse(inode, offset, len);
>  	if (ret)
>  		goto out_unlock;
>  
> @@ -1243,7 +1241,6 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
>  		f2fs_i_size_write(inode, new_size);
>  out_unlock:
>  	up_write(&F2FS_I(inode)->i_mmap_sem);
> -	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	return ret;
>  }
>  
> @@ -1418,9 +1415,6 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
>  
>  	f2fs_balance_fs(sbi, true);
>  
> -	/* avoid gc operation during block exchange */
> -	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> -
>  	down_write(&F2FS_I(inode)->i_mmap_sem);
>  	ret = f2fs_truncate_blocks(inode, i_size_read(inode), true);
>  	if (ret)
> @@ -1431,13 +1425,15 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
>  	if (ret)
>  		goto out;
>  
> -	truncate_pagecache(inode, offset);
> -
>  	pg_start = offset >> PAGE_SHIFT;
>  	pg_end = (offset + len) >> PAGE_SHIFT;
>  	delta = pg_end - pg_start;
>  	idx = (i_size_read(inode) + PAGE_SIZE - 1) / PAGE_SIZE;
>  
> +	/* avoid gc operation during block exchange */
> +	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> +	truncate_pagecache(inode, offset);
> +
>  	while (!ret && idx > pg_start) {
>  		nr = idx - pg_start;
>  		if (nr > delta)
> @@ -1451,6 +1447,7 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
>  					idx + delta, nr, false);
>  		f2fs_unlock_op(sbi);
>  	}
> +	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  
>  	/* write out all moved pages, if possible */
>  	filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
> @@ -1460,7 +1457,6 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
>  		f2fs_i_size_write(inode, new_size);
>  out:
>  	up_write(&F2FS_I(inode)->i_mmap_sem);
> -	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	return ret;
>  }
>  
> @@ -1707,8 +1703,6 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>  
>  	inode_lock(inode);
>  
> -	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> -
>  	if (f2fs_is_atomic_file(inode)) {
>  		if (is_inode_flag_set(inode, FI_ATOMIC_REVOKE_REQUEST))
>  			ret = -EINVAL;
> @@ -1719,6 +1713,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>  	if (ret)
>  		goto out;
>  
> +	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> +
>  	if (!get_dirty_pages(inode))
>  		goto skip_flush;
>  
> @@ -1726,18 +1722,20 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>  		"Unexpected flush for atomic writes: ino=%lu, npages=%u",
>  					inode->i_ino, get_dirty_pages(inode));
>  	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
> -	if (ret)
> +	if (ret) {
> +		up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  		goto out;
> +	}
>  skip_flush:
>  	set_inode_flag(inode, FI_ATOMIC_FILE);
>  	clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> -	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
> +	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  
> +	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
>  	F2FS_I(inode)->inmem_task = current;
>  	stat_inc_atomic_write(inode);
>  	stat_update_max_atomic_write(inode);
>  out:
> -	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	inode_unlock(inode);
>  	mnt_drop_write_file(filp);
>  	return ret;
> @@ -1755,9 +1753,9 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
>  	if (ret)
>  		return ret;
>  
> -	inode_lock(inode);
> +	f2fs_balance_fs(F2FS_I_SB(inode), true);
>  
> -	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> +	inode_lock(inode);
>  
>  	if (f2fs_is_volatile_file(inode)) {
>  		ret = -EINVAL;
> @@ -1783,7 +1781,6 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
>  		clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
>  		ret = -EINVAL;
>  	}
> -	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	inode_unlock(inode);
>  	mnt_drop_write_file(filp);
>  	return ret;
> @@ -2379,15 +2376,10 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
>  	}
>  
>  	inode_lock(src);
> -	down_write(&F2FS_I(src)->i_gc_rwsem[WRITE]);
>  	if (src != dst) {
>  		ret = -EBUSY;
>  		if (!inode_trylock(dst))
>  			goto out;
> -		if (!down_write_trylock(&F2FS_I(dst)->i_gc_rwsem[WRITE])) {
> -			inode_unlock(dst);
> -			goto out;
> -		}
>  	}
>  
>  	ret = -EINVAL;
> @@ -2432,6 +2424,14 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
>  		goto out_unlock;
>  
>  	f2fs_balance_fs(sbi, true);
> +
> +	down_write(&F2FS_I(src)->i_gc_rwsem[WRITE]);
> +	if (src != dst) {
> +		ret = -EBUSY;
> +		if (!down_write_trylock(&F2FS_I(dst)->i_gc_rwsem[WRITE]))
> +			goto out_src;
> +	}
> +
>  	f2fs_lock_op(sbi);
>  	ret = __exchange_data_block(src, dst, pos_in >> F2FS_BLKSIZE_BITS,
>  				pos_out >> F2FS_BLKSIZE_BITS,
> @@ -2444,13 +2444,15 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
>  			f2fs_i_size_write(dst, dst_osize);
>  	}
>  	f2fs_unlock_op(sbi);
> -out_unlock:
> -	if (src != dst) {
> +
> +	if (src != dst)
>  		up_write(&F2FS_I(dst)->i_gc_rwsem[WRITE]);
> +out_src:
> +	up_write(&F2FS_I(src)->i_gc_rwsem[WRITE]);
> +out_unlock:
> +	if (src != dst)
>  		inode_unlock(dst);
> -	}
>  out:
> -	up_write(&F2FS_I(src)->i_gc_rwsem[WRITE]);
>  	inode_unlock(src);
>  	return ret;
>  }
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index e352fbd33848..d816c328f02b 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -884,6 +884,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  			if (!down_write_trylock(
>  				&F2FS_I(inode)->i_gc_rwsem[WRITE])) {
>  				iput(inode);
> +				sbi->skipped_gc_rwsem++;
>  				continue;
>  			}
>  
> @@ -913,6 +914,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  					continue;
>  				if (!down_write_trylock(
>  						&fi->i_gc_rwsem[WRITE])) {
> +					sbi->skipped_gc_rwsem++;
>  					up_write(&fi->i_gc_rwsem[READ]);
>  					continue;
>  				}
> @@ -1062,6 +1064,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  				prefree_segments(sbi));
>  
>  	cpc.reason = __get_cp_reason(sbi);
> +	sbi->skipped_gc_rwsem = 0;
>  gc_more:
>  	if (unlikely(!(sbi->sb->s_flags & SB_ACTIVE))) {
>  		ret = -EINVAL;
> @@ -1103,7 +1106,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  	total_freed += seg_freed;
>  
>  	if (gc_type == FG_GC) {
> -		if (sbi->skipped_atomic_files[FG_GC] > last_skipped)
> +		if (sbi->skipped_atomic_files[FG_GC] > last_skipped ||
> +						sbi->skipped_gc_rwsem)
>  			skipped_round++;
>  		last_skipped = sbi->skipped_atomic_files[FG_GC];
>  		round++;
> @@ -1112,15 +1116,23 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  	if (gc_type == FG_GC)
>  		sbi->cur_victim_sec = NULL_SEGNO;
>  
> -	if (!sync) {
> -		if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
> -			if (skipped_round > MAX_SKIP_ATOMIC_COUNT &&
> -				skipped_round * 2 >= round)
> -				f2fs_drop_inmem_pages_all(sbi, true);
> +	if (sync)
> +		goto stop;
> +
> +	if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
> +		if (skipped_round <= MAX_SKIP_GC_COUNT ||
> +					skipped_round * 2 < round) {
>  			segno = NULL_SEGNO;
>  			goto gc_more;
>  		}
>  
> +		if (sbi->skipped_atomic_files[FG_GC] == last_skipped &&

For fggc, sbi->skipped_atomic_files[FG_GC] should always be last_skipped, since
we assigned above.

> +				sbi->skipped_atomic_files[FG_GC] >
> +						sbi->skipped_gc_rwsem) {
> +			f2fs_drop_inmem_pages_all(sbi, true);
> +			segno = NULL_SEGNO;
> +			goto gc_more;

I guess what you mean is:

atomic_skipped = sbi->skipped_atomic_files[FG_GC] - last_skipped;

if (atomic_skipped && atomic_skipped > sbi->skipped_gc_rwsem)
	f2fs_drop_inmem_pages_all();

Is that right?

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 870b337e9f7f..40f103508432 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1142,7 +1142,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 		.iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
 	};
 	unsigned long long last_skipped = sbi->skipped_atomic_files[FG_GC];
-	unsigned int skipped_round = 0, round = 0;
+	unsigned int skipped_round = 0, round = 0, atomic_skipped;

 	trace_f2fs_gc_begin(sbi->sb, sync, background,
 				get_pages(sbi, F2FS_DIRTY_NODES),
@@ -1196,8 +1196,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 	total_freed += seg_freed;

 	if (gc_type == FG_GC) {
-		if (sbi->skipped_atomic_files[FG_GC] > last_skipped ||
-						sbi->skipped_gc_rwsem)
+		atomic_skipped =
+			sbi->skipped_atomic_files[FG_GC] - last_skipped;
+		if (atomic_skipped || sbi->skipped_gc_rwsem)
 			skipped_round++;
 		last_skipped = sbi->skipped_atomic_files[FG_GC];
 		round++;
@@ -1216,9 +1217,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 			goto gc_more;
 		}

-		if (sbi->skipped_atomic_files[FG_GC] == last_skipped &&
-				sbi->skipped_atomic_files[FG_GC] >
-						sbi->skipped_gc_rwsem) {
+		if (atomic_skipped && atomic_skipped > sbi->skipped_gc_rwsem) {
 			f2fs_drop_inmem_pages_all(sbi, true);
 			segno = NULL_SEGNO;
 			goto gc_more;

Thanks,

> +		}
>  		if (gc_type == FG_GC)
>  			ret = f2fs_write_checkpoint(sbi, &cpc);
>  	}
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 3662e1f429b4..f4ac006dac43 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -445,8 +445,10 @@ int f2fs_commit_inmem_pages(struct inode *inode)
>  	int err;
>  
>  	f2fs_balance_fs(sbi, true);
> -	f2fs_lock_op(sbi);
>  
> +	down_write(&fi->i_gc_rwsem[WRITE]);
> +
> +	f2fs_lock_op(sbi);
>  	set_inode_flag(inode, FI_ATOMIC_COMMIT);
>  
>  	mutex_lock(&fi->inmem_lock);
> @@ -461,6 +463,8 @@ int f2fs_commit_inmem_pages(struct inode *inode)
>  	clear_inode_flag(inode, FI_ATOMIC_COMMIT);
>  
>  	f2fs_unlock_op(sbi);
> +	up_write(&fi->i_gc_rwsem[WRITE]);
> +
>  	return err;
>  }
>  
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 50495515f0a0..b3d9e317ff0c 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -215,7 +215,7 @@ struct segment_allocation {
>  #define IS_DUMMY_WRITTEN_PAGE(page)			\
>  		(page_private(page) == (unsigned long)DUMMY_WRITTEN_PAGE)
>  
> -#define MAX_SKIP_ATOMIC_COUNT			16
> +#define MAX_SKIP_GC_COUNT			16
>  
>  struct inmem_pages {
>  	struct list_head list;
> 


  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-30  1:32 [PATCH] " Jaegeuk Kim
2018-07-30  3:29 ` Chao Yu
2018-07-30  4:18   ` Jaegeuk Kim
2018-07-30  6:36     ` Chao Yu
2018-07-30  9:08       ` Jaegeuk Kim
2018-07-30  9:28         ` Chao Yu
2018-07-30 10:00           ` Jaegeuk Kim
2018-08-04  2:31             ` [f2fs-dev] " Chao Yu
2018-08-12 10:24               ` Chao Yu
2018-08-13 20:12                 ` Jaegeuk Kim
2018-08-14  6:21                   ` Chao Yu
2018-08-04 22:29 ` [PATCH v2] " Jaegeuk Kim
2018-08-05 14:42   ` [f2fs-dev] " Chao Yu
2018-08-05 16:08     ` Jaegeuk Kim
2018-08-05 16:34   ` [f2fs-dev] [PATCH v3] " Jaegeuk Kim
2018-08-09  1:44     ` Chao Yu [this message]
2018-08-09 19:59       ` Jaegeuk Kim
2018-08-10  1:36         ` Chao Yu
2018-08-10  1:46           ` Jaegeuk Kim
2018-08-20  7:13             ` Chao Yu

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