From a9759f2de38a3443d5107bddde03b4f3f550060e Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 7 Dec 2007 14:07:08 +1100 Subject: [PATCH] [XFS] kill superflous buffer locking (2nd attempt) 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:30156a Signed-off-by: Christoph Hellwig Signed-off-by: Lachlan McIlroy --- fs/xfs/linux-2.6/xfs_buf.c | 55 ++++---------------------------------- fs/xfs/linux-2.6/xfs_buf.h | 1 - 2 files changed, 5 insertions(+), 51 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c index 522cfaa7025..302273f8e2a 100644 --- a/fs/xfs/linux-2.6/xfs_buf.c +++ b/fs/xfs/linux-2.6/xfs_buf.c @@ -387,8 +387,6 @@ _xfs_buf_lookup_pages( if (unlikely(page == NULL)) { if (flags & XBF_READ_AHEAD) { bp->b_page_count = i; - for (i = 0; i < bp->b_page_count; i++) - unlock_page(bp->b_pages[i]); return -ENOMEM; } @@ -418,24 +416,17 @@ _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++; } } + unlock_page(page); bp->b_pages[i] = page; 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 +743,6 @@ 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; @@ -1099,25 +1089,13 @@ 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 @@ -1148,10 +1126,6 @@ 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 +1136,12 @@ 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 +1164,7 @@ _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 +1181,6 @@ _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); diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h index b5908a34b15..a3d207de48b 100644 --- a/fs/xfs/linux-2.6/xfs_buf.h +++ b/fs/xfs/linux-2.6/xfs_buf.h @@ -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 */ -- 2.20.1