rbd: use the correct length for format 2 object names

commit 3a96d5cd7bdce45d5dded75c3a62d4fb98050280 upstream.

[Backported for 3.9-stable.
'kmalloc(MAX_OBJ_NAME_SIZE + 1, GFP_NOIO)' was changed as
'kmem_cache_alloc(rbd_segment_name_cache, GFP_NOIO)' in 78c2a44
since 3.10-rc1, and 78c2a44 is relied on a big patchset, so restore
it as 3.9 did.]

Format 2 objects use 16 characters for the object name suffix to be
able to express the full 64-bit range of object numbers. Format 1
images only use 12 characters for this. Using 12-character names for
format 2 caused userspace and kernel rbd clients to read differently
named objects, which made an image written by one client look empty to
the other client.

Reported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Reviewed-by: Lingzhu Xiang <lxiang@redhat.com>
Signed-off-by: Zhouping Liu <zliu@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index fe333e4b731e2c3a3bd8aad50ce813693b75781f..c2b1427e34680c87ef3ad0cf4347b66f765d3454 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -833,12 +833,16 @@ static const char *rbd_segment_name(struct rbd_device *rbd_dev, u64 offset)
        char *name;
        u64 segment;
        int ret;
+       char *name_format;
 
        name = kmalloc(MAX_OBJ_NAME_SIZE + 1, GFP_NOIO);
        if (!name)
                return NULL;
        segment = offset >> rbd_dev->header.obj_order;
-       ret = snprintf(name, MAX_OBJ_NAME_SIZE + 1, "%s.%012llx",
+       name_format = "%s.%012llx";
+       if (rbd_dev->image_format == 2)
+               name_format = "%s.%016llx";
+       ret = snprintf(name, MAX_OBJ_NAME_SIZE + 1, name_format,
                        rbd_dev->header.object_prefix, segment);
        if (ret < 0 || ret > MAX_OBJ_NAME_SIZE) {
                pr_err("error formatting segment name for #%llu (%d)\n",