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Commit c40ea741 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Lachlan McIlroy
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[XFS] kill superflous buffer locking 



There is no need to lock any page in xfs_buf.c because we operate on our
own address_space and all locking is covered by the buffer semaphore. If
we ever switch back to main blockdeive address_space as suggested e.g. for
fsblock with a similar scheme the locking will have to be totally revised
anyway because the current scheme is neither correct nor coherent with
itself.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:29845a

Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
Signed-off-by: default avatarTim Shimmin <tes@sgi.com>
parent 0771fb45

fs/xfs/linux-2.6/xfs_buf.c

+5 −48
Original line number Diff line number Diff line
@@ -409,6 +409,7 @@ _xfs_buf_lookup_pages( 
			congestion_wait(WRITE, HZ/50);

			goto retry;

		}

		unlock_page(page);



		XFS_STATS_INC(xb_page_found);
@@ -418,10 +419,7 @@ _xfs_buf_lookup_pages( 
		ASSERT(!PagePrivate(page));

		if (!PageUptodate(page)) {

			page_count--;

			if (blocksize >= PAGE_CACHE_SIZE) {

				if (flags & XBF_READ)

					bp->b_locked = 1;

			} else if (!PagePrivate(page)) {

			if (blocksize < PAGE_CACHE_SIZE && !PagePrivate(page)) {

				if (test_page_region(page, offset, nbytes))

					page_count++;

			}
@@ -431,11 +429,6 @@ _xfs_buf_lookup_pages( 
		offset = 0;

	}



	if (!bp->b_locked) {

		for (i = 0; i < bp->b_page_count; i++)

			unlock_page(bp->b_pages[i]);

	}



	if (page_count == bp->b_page_count)

		bp->b_flags |= XBF_DONE;
@@ -752,7 +745,6 @@ xfs_buf_associate_memory( 
		bp->b_pages[i] = mem_to_page((void *)pageaddr);

		pageaddr += PAGE_CACHE_SIZE;

	}

	bp->b_locked = 0;



	bp->b_count_desired = len;

	bp->b_buffer_length = buflen;
@@ -1099,26 +1091,14 @@ xfs_buf_iostart( 
	return status;

}



STATIC_INLINE int

_xfs_buf_iolocked(

	xfs_buf_t		*bp)

{

	ASSERT(bp->b_flags & (XBF_READ | XBF_WRITE));

	if (bp->b_flags & XBF_READ)

		return bp->b_locked;

	return 0;

}



STATIC_INLINE void

_xfs_buf_ioend(

	xfs_buf_t		*bp,

	int			schedule)

{

	if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {

		bp->b_locked = 0;

	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)

		xfs_buf_ioend(bp, schedule);

}

}



STATIC void

xfs_buf_bio_end_io(
@@ -1148,10 +1128,6 @@ xfs_buf_bio_end_io( 


		if (--bvec >= bio->bi_io_vec)

			prefetchw(&bvec->bv_page->flags);



		if (_xfs_buf_iolocked(bp)) {

			unlock_page(page);

		}

	} while (bvec >= bio->bi_io_vec);



	_xfs_buf_ioend(bp, 1);
@@ -1162,13 +1138,12 @@ STATIC void 
_xfs_buf_ioapply(

	xfs_buf_t		*bp)

{

	int			i, rw, map_i, total_nr_pages, nr_pages;

	int			rw, map_i, total_nr_pages, nr_pages;

	struct bio		*bio;

	int			offset = bp->b_offset;

	int			size = bp->b_count_desired;

	sector_t		sector = bp->b_bn;

	unsigned int		blocksize = bp->b_target->bt_bsize;

	int			locking = _xfs_buf_iolocked(bp);



	total_nr_pages = bp->b_page_count;

	map_i = 0;
@@ -1191,7 +1166,7 @@ _xfs_buf_ioapply( 
	 * filesystem block size is not smaller than the page size.

	 */

	if ((bp->b_buffer_length < PAGE_CACHE_SIZE) &&

	    (bp->b_flags & XBF_READ) && locking &&

	    (bp->b_flags & XBF_READ) &&

	    (blocksize >= PAGE_CACHE_SIZE)) {

		bio = bio_alloc(GFP_NOIO, 1);
@@ -1208,24 +1183,6 @@ _xfs_buf_ioapply( 
		goto submit_io;

	}



	/* Lock down the pages which we need to for the request */

	if (locking && (bp->b_flags & XBF_WRITE) && (bp->b_locked == 0)) {

		for (i = 0; size; i++) {

			int		nbytes = PAGE_CACHE_SIZE - offset;

			struct page	*page = bp->b_pages[i];



			if (nbytes > size)

				nbytes = size;



			lock_page(page);



			size -= nbytes;

			offset = 0;

		}

		offset = bp->b_offset;

		size = bp->b_count_desired;

	}



next_chunk:

	atomic_inc(&bp->b_io_remaining);

	nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);

fs/xfs/linux-2.6/xfs_buf.h

+0 −1
Original line number Diff line number Diff line
@@ -143,7 +143,6 @@ typedef struct xfs_buf { 
	void			*b_fspriv2;

	void			*b_fspriv3;

	unsigned short		b_error;	/* error code on I/O */

	unsigned short		b_locked;	/* page array is locked */

	unsigned int		b_page_count;	/* size of page array */

	unsigned int		b_offset;	/* page offset in first page */

	struct page		**b_pages;	/* array of page pointers */