Author: kib
Date: Tue Mar 19 14:27:14 2013
New Revision: 248510
URL: http://svnweb.freebsd.org/changeset/base/248510
Log:
Add a helper function vfs_bio_bzero_buf() to zero the portion of the
buffer, transparently handling mapped or unmapped buffers. Its intent
is to replace the use of bzero(bp->b_data) in cases where the buffer
might be unmapped, to avoid unneeded upgrades.
Sponsored by: The FreeBSD Foundation
Tested by: pho
Modified:
head/sys/kern/vfs_bio.c
head/sys/sys/buf.h
Modified: head/sys/kern/vfs_bio.c
==============================================================================
--- head/sys/kern/vfs_bio.c Tue Mar 19 14:15:41 2013 (r248509)
+++ head/sys/kern/vfs_bio.c Tue Mar 19 14:27:14 2013 (r248510)
@@ -4176,6 +4176,32 @@ unlock:
bp->b_resid = 0;
}
+void
+vfs_bio_bzero_buf(struct buf *bp, int base, int size)
+{
+ vm_page_t m;
+ int i, n;
+
+ if ((bp->b_flags & B_UNMAPPED) == 0) {
+ BUF_CHECK_MAPPED(bp);
+ bzero(bp->b_data + base, size);
+ } else {
+ BUF_CHECK_UNMAPPED(bp);
+ n = PAGE_SIZE - (base & PAGE_MASK);
+ VM_OBJECT_WLOCK(bp->b_bufobj->bo_object);
+ for (i = base / PAGE_SIZE; size > 0 && i < bp->b_npages; ++i) {
+ m = bp->b_pages[i];
+ if (n > size)
+ n = size;
+ pmap_zero_page_area(m, base & PAGE_MASK, n);
+ base += n;
+ size -= n;
+ n = PAGE_SIZE;
+ }
+ VM_OBJECT_WUNLOCK(bp->b_bufobj->bo_object);
+ }
+}
+
/*
* vm_hold_load_pages and vm_hold_free_pages get pages into
* a buffers address space. The pages are anonymous and are
Modified: head/sys/sys/buf.h
==============================================================================
--- head/sys/sys/buf.h Tue Mar 19 14:15:41 2013 (r248509)
+++ head/sys/sys/buf.h Tue Mar 19 14:27:14 2013 (r248510)
@@ -519,6 +519,7 @@ int cluster_read(struct vnode *, u_quad_
struct ucred *, long, int, int, struct buf **);
int cluster_wbuild(struct vnode *, long, daddr_t, int, int);
void cluster_write(struct vnode *, struct buf *, u_quad_t, int, int);
+void vfs_bio_bzero_buf(struct buf *bp, int base, int size);
void vfs_bio_set_valid(struct buf *, int base, int size);
void vfs_bio_clrbuf(struct buf *);
void vfs_busy_pages(struct buf *, int clear_modify);
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