Commit 0e6e847f which introduced xfs_buf_allocate_memory() function has a bug
causing the function to overestimate the number of necessary pages. The problem
is that xfs_buf_alloc() sets b_bn to -1 and thus effectively every buffer is
straddling a page boundary which causes xfs_buf_allocate_memory() to allocate
two pages and use vmalloc() for access which slows things down.
Fix the code to use correct block number.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/xfs/xfs_buf.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 172d3cc..b67cc83 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -296,6 +296,7 @@ xfs_buf_free(
STATIC int
xfs_buf_allocate_memory(
xfs_buf_t *bp,
+ xfs_daddr_t blkno,
uint flags)
{
size_t size;
@@ -334,8 +335,8 @@ xfs_buf_allocate_memory(
}
use_alloc_page:
- start = BBTOB(bp->b_bn) >> PAGE_SHIFT;
- end = (BBTOB(bp->b_bn + bp->b_length) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ start = BBTOB(blkno) >> PAGE_SHIFT;
+ end = (BBTOB(blkno + bp->b_length) + PAGE_SIZE - 1) >> PAGE_SHIFT;
page_count = end - start;
error = _xfs_buf_get_pages(bp, page_count, flags);
if (unlikely(error))
@@ -552,7 +553,7 @@ xfs_buf_get(
if (unlikely(!new_bp))
return NULL;
- error = xfs_buf_allocate_memory(new_bp, flags);
+ error = xfs_buf_allocate_memory(new_bp, blkno, flags);
if (error) {
kmem_zone_free(xfs_buf_zone, new_bp);
return NULL;
--
1.7.1
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
