[libvirt] [PATCH] virfile: safezero: align mmap offset to page size
mmap's offset must be aligned to page size or mapping will fail.
mmap-based safezero is only used if posix_fallocate isn't available.
Signed-off-by: Oskari Saarenmaa <os(a)ohmu.fi>
---
src/util/virfile.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/src/util/virfile.c b/src/util/virfile.c
index 20ca89f..16f8101 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -1038,9 +1038,16 @@ safezero(int fd, off_t offset, off_t len)
int
safezero(int fd, off_t offset, off_t len)
{
+ static long pagemask = 0;
+ off_t map_skip;
int r;
char *buf;
+ /* align offset and length, rounding offset down and length up */
+ if (pagemask == 0)
+ pagemask = ~(sysconf(_SC_PAGESIZE) - 1);
+ map_skip = offset - (offset & pagemask);
+
/* memset wants the mmap'ed file to be present on disk so create a
* sparse file
*/
@@ -1048,12 +1055,13 @@ safezero(int fd, off_t offset, off_t len)
if (r < 0)
return -1;
- buf = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
+ buf = mmap(NULL, len + map_skip, PROT_READ | PROT_WRITE, MAP_SHARED,
+ fd, offset - map_skip);
if (buf == MAP_FAILED)
return -1;
- memset(buf, 0, len);
- munmap(buf, len);
+ memset(buf + map_skip, 0, len);
+ munmap(buf, len + map_skip);
return 0;
}
--
1.8.3.1