[PATCH] invalidate_bdev() speedup

We can immediately bail from invalidate_bdev() if the blockdev has no
pagecache.

This solves the huge IPI storms which hald is causing on the big ia64
machines when it polls CDROM drives.

Acked-by: Jes Sorensen <jes@sgi.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 3660dcb97591..71649ef9b658 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -470,13 +470,18 @@ out:
    pass does the actual I/O. */
 void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
 {
+        struct address_space *mapping = bdev->bd_inode->i_mapping;
+
+        if (mapping->nrpages == 0)
+                return;
+
         invalidate_bh_lrus();
         /*
          * FIXME: what about destroy_dirty_buffers?
          * We really want to use invalidate_inode_pages2() for
          * that, but not until that's cleaned up.
          */
-        invalidate_inode_pages(bdev->bd_inode->i_mapping);
+        invalidate_inode_pages(mapping);
 }
 
 /*