linux-kernel - Re: [PATCH v2] f2fs: relax migratepage for atomic written page

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Date:   Thu, 6 Jul 2017 14:49:26 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v2] f2fs: relax migratepage for atomic written page

In order to avoid lock contention for atomic written pages, we'd better give
EBUSY in f2fs_migrate_page when mode is asynchronous. We expect it will be
released soon as transaction commits.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---

Change log from v1:
 - return -EBUSY when mode is MIGRATE_ASYNC or MIGRATE_SYNC_LIGHT

 fs/f2fs/data.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 85ac3a63cce6..74c31cb203e2 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2206,8 +2206,12 @@ int f2fs_migrate_page(struct address_space *mapping,
 	BUG_ON(PageWriteback(page));
 
 	/* migrating an atomic written page is safe with the inmem_lock hold */
-	if (atomic_written && !mutex_trylock(&fi->inmem_lock))
-		return -EAGAIN;
+	if (atomic_written) {
+		if (mode != MIGRATE_SYNC)
+			return -EBUSY;
+		if (!mutex_trylock(&fi->inmem_lock))
+			return -EAGAIN;
+	}
 
 	/*
 	 * A reference is expected if PagePrivate set when move mapping,
-- 
2.13.0.rc1.294.g07d810a77f-goog