NTFS: Improve scalability by changing the driver global spin lock in

      fs/ntfs/aops.c::ntfs_end_buffer_async_read() to a bit spin lock
      in the first buffer head of a page.

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

2 files changed, 12 insertions, 6 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index 029f856c56c0..32a4150ebcb2 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -86,6 +86,9 @@ ToDo/Notes:
         - Fix fs/ntfs/aops.c::ntfs_{read,write}_block() to handle the case
           where a concurrent truncate has truncated the runlist under our feet.
         - Fix page_has_buffers()/page_buffers() handling in fs/ntfs/aops.c.
+        - In fs/ntfs/aops.c::ntfs_end_buffer_async_read(), use a bit spin lock
+          in the first buffer head instead of a driver global spin lock to
+          improve scalability.
 
 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 52e1aff98b00..950b686f02d3 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -55,9 +55,8 @@
  */
 static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
 {
-        static DEFINE_SPINLOCK(page_uptodate_lock);
         unsigned long flags;
-        struct buffer_head *tmp;
+        struct buffer_head *first, *tmp;
         struct page *page;
         ntfs_inode *ni;
         int page_uptodate = 1;
@@ -89,11 +88,13 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
                 }
         } else {
                 clear_buffer_uptodate(bh);
+                SetPageError(page);
                 ntfs_error(ni->vol->sb, "Buffer I/O error, logical block %llu.",
                                 (unsigned long long)bh->b_blocknr);
-                SetPageError(page);
         }
-        spin_lock_irqsave(&page_uptodate_lock, flags);
+        first = page_buffers(page);
+        local_irq_save(flags);
+        bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
         clear_buffer_async_read(bh);
         unlock_buffer(bh);
         tmp = bh;
@@ -108,7 +109,8 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
                 }
                 tmp = tmp->b_this_page;
         } while (tmp != bh);
-        spin_unlock_irqrestore(&page_uptodate_lock, flags);
+        bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+        local_irq_restore(flags);
         /*
          * If none of the buffers had errors then we can set the page uptodate,
          * but we first have to perform the post read mst fixups, if the
@@ -141,7 +143,8 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
         unlock_page(page);
         return;
 still_busy:
-        spin_unlock_irqrestore(&page_uptodate_lock, flags);
+        bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+        local_irq_restore(flags);
         return;
 }