mm: optimize kill_bdev() (f9a14399) · Commits · 戴 / test

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>

fs/block_dev.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

fs/buffer.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

include/linux/buffer_head.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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));

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