NTFS: Optimize fs/ntfs/aops.c::ntfs_write_block() by extending the page

      lock protection over the buffer submission for i/o which allows the
      removal of the get_bh()/put_bh() pairs for each buffer.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

1 files changed, 3 insertions, 10 deletions

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 6f2954aac5a2..821dad7d14c8 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -735,7 +735,7 @@ lock_retry_remap:
         /* For the error case, need to reset bh to the beginning. */
         bh = head;
 
-        /* Just an optimization, so ->readpage() isn't called later. */
+        /* Just an optimization, so ->readpage() is not called later. */
         if (unlikely(!PageUptodate(page))) {
                 int uptodate = 1;
                 do {
@@ -751,7 +751,6 @@ lock_retry_remap:
 
         /* Setup all mapped, dirty buffers for async write i/o. */
         do {
-                get_bh(bh);
                 if (buffer_mapped(bh) && buffer_dirty(bh)) {
                         lock_buffer(bh);
                         if (test_clear_buffer_dirty(bh)) {
@@ -789,14 +788,8 @@ lock_retry_remap:
 
         BUG_ON(PageWriteback(page));
         set_page_writeback(page);       /* Keeps try_to_free_buffers() away. */
-        unlock_page(page);
 
-        /*
-         * Submit the prepared buffers for i/o. Note the page is unlocked,
-         * and the async write i/o completion handler can end_page_writeback()
-         * at any time after the *first* submit_bh(). So the buffers can then
-         * disappear...
-         */
+        /* Submit the prepared buffers for i/o. */
         need_end_writeback = TRUE;
         do {
                 struct buffer_head *next = bh->b_this_page;
@@ -804,9 +797,9 @@ lock_retry_remap:
                         submit_bh(WRITE, bh);
                         need_end_writeback = FALSE;
                 }
-                put_bh(bh);
                 bh = next;
         } while (bh != head);
+        unlock_page(page);
 
         /* If no i/o was started, need to end_page_writeback(). */
         if (unlikely(need_end_writeback))