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

[Jaegeuk Kim]

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 <jaeg...@kernel.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