mm: optimize kill_bdev()

Remove duplicate work in kill_bdev().

It currently invalidates and then truncates the bdev's mapping.
invalidate_mapping_pages() will opportunistically remove pages from the
mapping.  And truncate_inode_pages() will forcefully remove all pages.

The only thing truncate doesn't do is flush the bh lrus.  So do that
explicitly.  This avoids (very unlikely) but possible invalid lookup
results if the same bdev is quickly re-issued.

It also will prevent extreme kernel latencies which are observed when
blockdevs which have a large amount of pagecache are unmounted, by avoiding
invalidate_mapping_pages() on that path.  invalidate_mapping_pages() has no
cond_resched (it can be called under spinlock), whereas truncate_inode_pages()
has one.

[akpm@linux-foundation.org: restore nrpages==0 optimisation]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 21e59acbcfdf29acbad970d622cb9621efc125c0..6fe49b9349ea465db443080b3f535031b44fdfc5 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -55,10 +55,12 @@ static sector_t max_block(struct block_device *bdev)
        return retval;
 }
 
-/* Kill _all_ buffers, dirty or not.. */
+/* Kill _all_ buffers and pagecache , dirty or not.. */
 static void kill_bdev(struct block_device *bdev)
 {
-       invalidate_bdev(bdev);
+       if (bdev->bd_inode->i_mapping->nrpages == 0)
+               return;
+       invalidate_bh_lrus();
        truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
 }      
 

diff --git a/fs/buffer.c b/fs/buffer.c
index 630df3e6fe0c77a07b9d0caaf9edf54a29435dff..80291aad6de6d6dedaa0643e536db3166ca7eff2 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -44,7 +44,6 @@
 #include <linux/bit_spinlock.h>
 
 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
-static void invalidate_bh_lrus(void);
 
 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
 
@@ -1403,7 +1402,7 @@ static void invalidate_bh_lru(void *arg)
        put_cpu_var(bh_lrus);
 }
        
-static void invalidate_bh_lrus(void)
+void invalidate_bh_lrus(void)
 {
        on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
 }

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 632c50b21386d618146ad75995c99566c7175ec3..5c6e12853a9bb758918e809de1c8a94c56a731f6 100644 (file)
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -182,6 +182,7 @@ void __brelse(struct buffer_head *);
 void __bforget(struct buffer_head *);
 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
+void invalidate_bh_lrus(void);
 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 void free_buffer_head(struct buffer_head * bh);
 void FASTCALL(unlock_buffer(struct buffer_head *bh));