vfs: Move mark_inode_dirty() from under page lock in generic_write_end()

There's no need to call mark_inode_dirty() under page lock in
generic_write_end(). It unnecessarily makes hold time of page lock longer
and more importantly it forces locking order of page lock and transaction
start for journaling filesystems.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 11 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 0f51c0f7c266..f4b033237a02 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2061,6 +2061,7 @@ int generic_write_end(struct file *file, struct address_space *mapping,
                         struct page *page, void *fsdata)
 {
         struct inode *inode = mapping->host;
+        int i_size_changed = 0;
 
         copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
 
@@ -2073,12 +2074,21 @@ int generic_write_end(struct file *file, struct address_space *mapping,
          */
         if (pos+copied > inode->i_size) {
                 i_size_write(inode, pos+copied);
-                mark_inode_dirty(inode);
+                i_size_changed = 1;
         }
 
         unlock_page(page);
         page_cache_release(page);
 
+        /*
+         * Don't mark the inode dirty under page lock. First, it unnecessarily
+         * makes the holding time of page lock longer. Second, it forces lock
+         * ordering of page lock and transaction start for journaling
+         * filesystems.
+         */
+        if (i_size_changed)
+                mark_inode_dirty(inode);
+
         return copied;
 }
 EXPORT_SYMBOL(generic_write_end);