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>

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index 4b8666d..10fc238 100644 (file)
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -81,6 +81,9 @@ ToDo/Notes:
          only zeroes.
        - Fixup handling of sparse, compressed, and encrypted attributes in
          fs/ntfs/aops.c::ntfs_writepage().
+       - 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.
 
 2.1.23 - Implement extension of resident files and make writing safe as well as
         many bug fixes, cleanups, and enhancements...

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 6f2954a..821dad7 100644 (file)
--- 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))