[PATCH] __block_write_full_page speedup

Remove all those get_bh()'s and put_bh()'s by extending lock_page() to cover
the troublesome regions.

(get_bh() and put_bh() happen every time whereas contention on a page's lock
in there happens basically never).

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 5 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index bc75f2e7b274..6f2c3303a443 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1826,7 +1826,6 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
                 }
                 if (test_clear_buffer_dirty(bh)) {
                         mark_buffer_async_write(bh);
-                        get_bh(bh);
                         last_bh = bh;
                 } else {
                         unlock_buffer(bh);
@@ -1839,20 +1838,19 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
          */
         BUG_ON(PageWriteback(page));
         set_page_writeback(page);
-        unlock_page(page);
 
         do {
                 struct buffer_head *next = bh->b_this_page;
                 if (buffer_async_write(bh)) {
                         submit_bh(WRITE, bh);
                         nr_underway++;
-                        put_bh(bh);
                         if (bh == last_bh)
                                 break;
                 }
                 bh = next;
         } while (bh != head);
         bh = head;
+        unlock_page(page);
 
         err = 0;
 done:
@@ -1894,7 +1892,6 @@ recover:
                 if (buffer_mapped(bh) && buffer_dirty(bh)) {
                         lock_buffer(bh);
                         mark_buffer_async_write(bh);
-                        get_bh(bh);
                         last_bh = bh;
                 } else {
                         /*
@@ -1914,7 +1911,6 @@ recover:
                         clear_buffer_dirty(bh);
                         submit_bh(WRITE, bh);
                         nr_underway++;
-                        put_bh(bh);
                         if (bh == last_bh)
                                 break;
                 }