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[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 <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
This commit is contained in:
Christoph Hellwig 2007-12-07 14:07:08 +11:00 committed by Lachlan McIlroy
parent 40ebd81d1a
commit a9759f2de3
2 changed files with 5 additions and 51 deletions
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55
fs/xfs/linux-2.6/xfs_buf.c
View File

@ -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);

1
fs/xfs/linux-2.6/xfs_buf.h
View File

@ -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 */