Re: [PATCH 4/4] f2fs: call f2fs_balance_fs only when node was changed

[Chao Yu <chao2.yu@samsung.com>]

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Wednesday, December 23, 2015 9:00 AM
> To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> linux-f2fs-devel@lists.sourceforge.net
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 4/4] f2fs: call f2fs_balance_fs only when node was changed
> 
> If user tries to update or read data, we don't need to call f2fs_balance_fs
> which triggers f2fs_gc, which increases unnecessary long latency.

One missing case is get_data_block_dio, how about also covering it based on
following patch?


>From 7175efac7473e7a04285055c69edfb7432f8ca4e Mon Sep 17 00:00:00 2001
From: Chao Yu <chao2.yu@samsung.com>
Date: Wed, 23 Dec 2015 17:11:43 +0800
Subject: [PATCH] f2fs: reduce covered region of sbi->cp_rwsem in
 f2fs_map_blocks

Only cover sbi->cp_rwsem on one dnode page's allocation and modification
instead of multiple's in f2fs_map_blocks, it can reduce the covered region
of cp_rwsem, then we can avoid potential long time delay for concurrent
checkpointer.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 fs/f2fs/data.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8f8f8b0..3c83b16 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -594,7 +594,7 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 	}
 
 	if (create)
-		f2fs_lock_op(F2FS_I_SB(inode));
+		f2fs_lock_op(sbi);
 
 	/* When reading holes, we need its node page */
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
@@ -651,6 +651,11 @@ get_next:
 		allocated = false;
 		f2fs_put_dnode(&dn);
 
+		if (create) {
+			f2fs_unlock_op(sbi);
+			f2fs_lock_op(sbi);
+		}
+
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
 		err = get_dnode_of_data(&dn, pgofs, mode);
 		if (err) {
@@ -706,7 +711,7 @@ put_out:
 	f2fs_put_dnode(&dn);
 unlock_out:
 	if (create)
-		f2fs_unlock_op(F2FS_I_SB(inode));
+		f2fs_unlock_op(sbi);
 out:
 	trace_f2fs_map_blocks(inode, map, err);
 	return err;
-- 
2.6.3



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