Use posix_memalign() for memory used to write bitmaps

This makes super[01].c properly align buffers used for the bitmap
using posix_memalign() to make sure the writes don't fail in case the
bitmap is opened using O_DIRECT.

This is based on https://bugzilla.redhat.com/show_bug.cgi?id=789898
and an initial patch by Alexander Murashkin.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/super0.c b/super0.c
index dab85db8d2d514560147956cdd77fa2994da928b..d53f025e6439dda4090250be55074d18b1a2946f 100644 (file)
--- a/super0.c
+++ b/super0.c
@@ -1065,13 +1065,11 @@ static int write_bitmap0(struct supertype *st, int fd)
        int rv = 0;
 
        int towrite, n;
-       char abuf[4096+4096];
-       char *buf = (char*)(((long)(abuf+4096))&~4095L);
+       void *buf;
 
        if (!get_dev_size(fd, NULL, &dsize))
                return 1;
 
-
        if (dsize < MD_RESERVED_SECTORS*512)
                return -1;
 
@@ -1082,6 +1080,9 @@ static int write_bitmap0(struct supertype *st, int fd)
        if (lseek64(fd, offset + 4096, 0)< 0LL)
                return 3;
 
+       if (posix_memalign(&buf, 4096, 4096))
+               return -ENOMEM;
+
        memset(buf, 0xff, 4096);
        memcpy(buf,  ((char*)sb)+MD_SB_BYTES, sizeof(bitmap_super_t));
        towrite = 60*1024;
@@ -1100,6 +1101,7 @@ static int write_bitmap0(struct supertype *st, int fd)
        if (towrite)
                rv = -2;
 
+       free(buf);
        return rv;
 }
 

diff --git a/super1.c b/super1.c
index cfa237a0d6b309c9aa38a1320aa6d6c8a49588e1..a18952a71e93e45199f6ac1d0a0dc3dc96aa3e42 100644 (file)
--- a/super1.c
+++ b/super1.c
@@ -1641,12 +1641,14 @@ static int write_bitmap1(struct supertype *st, int fd)
        struct mdp_superblock_1 *sb = st->sb;
        bitmap_super_t *bms = (bitmap_super_t*)(((char*)sb)+1024);
        int rv = 0;
-
+       void *buf;
        int towrite, n;
-       char buf[4096];
 
        locate_bitmap1(st, fd);
 
+       if (posix_memalign(&buf, 4096, 4096))
+               return -ENOMEM;
+
        memset(buf, 0xff, 4096);
        memcpy(buf, ((char*)sb)+1024, sizeof(bitmap_super_t));
 
@@ -1669,6 +1671,7 @@ static int write_bitmap1(struct supertype *st, int fd)
        if (towrite)
                rv = -2;
 
+       free(buf);
        return rv;
 }