From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH, v2 03/11] rbd: kill incore snap_names_len Date: Thu, 06 Sep 2012 10:36:22 -0500 Message-ID: <5048C2F6.8090102@inktank.com> References: <5037AB20.4000103@inktank.com> <5037ACC0.1000108@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:63065 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758152Ab2IFPg2 (ORCPT ); Thu, 6 Sep 2012 11:36:28 -0400 Received: by iahk25 with SMTP id k25so2179097iah.19 for ; Thu, 06 Sep 2012 08:36:27 -0700 (PDT) In-Reply-To: <5037ACC0.1000108@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org The only thing the on-disk snap_names_len field is needed is to size the buffer allocated to hold a copy of the snapshot names for an rbd image. So don't bother saving it in the in-core rbd_image_header structure. Just use a local variable to hold the required buffer size while it's needed. Move the code that actually copies the snapshot names up closer to where the required length is saved. Signed-off-by: Alex Elder --- v2: - Return -EIO rather than BUG_ON() as suggested by Yehuda. - Added a comment explaining why a memcpy() will not exceed the length of the on-disk buffer, in response to Yehuda's concern. drivers/block/rbd.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) Index: b/drivers/block/rbd.c =================================================================== --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -81,7 +81,6 @@ struct rbd_image_header { __u8 crypt_type; __u8 comp_type; struct ceph_snap_context *snapc; - u64 snap_names_len; u32 total_snaps; char *snap_names; @@ -534,12 +533,21 @@ static int rbd_header_from_disk(struct r header->object_prefix[len] = '\0'; if (snap_count) { - header->snap_names_len = le64_to_cpu(ondisk->snap_names_len); - BUG_ON(header->snap_names_len > (u64) SIZE_MAX); - header->snap_names = kmalloc(header->snap_names_len, - GFP_KERNEL); + u64 snap_names_len = le64_to_cpu(ondisk->snap_names_len); + + if (snap_names_len > (u64) SIZE_MAX) + return -EIO; + header->snap_names = kmalloc(snap_names_len, GFP_KERNEL); if (!header->snap_names) goto out_err; + /* + * Note that rbd_dev_v1_header_read() guarantees + * the ondisk buffer we're working with has + * snap_names_len bytes beyond the end of the + * snapshot id array, this memcpy() is safe. + */ + memcpy(header->snap_names, &ondisk->snaps[snap_count], + snap_names_len); size = snap_count * sizeof (*header->snap_sizes); header->snap_sizes = kmalloc(size, GFP_KERNEL); @@ -547,7 +555,6 @@ static int rbd_header_from_disk(struct r goto out_err; } else { WARN_ON(ondisk->snap_names_len); - header->snap_names_len = 0; header->snap_names = NULL; header->snap_sizes = NULL; } @@ -579,10 +586,6 @@ static int rbd_header_from_disk(struct r header->snap_sizes[i] = le64_to_cpu(ondisk->snaps[i].image_size); } - - /* copy snapshot names */ - memcpy(header->snap_names, &ondisk->snaps[snap_count], - header->snap_names_len); } return 0; @@ -592,7 +595,6 @@ out_err: header->snap_sizes = NULL; kfree(header->snap_names); header->snap_names = NULL; - header->snap_names_len = 0; kfree(header->object_prefix); header->object_prefix = NULL; @@ -660,7 +662,6 @@ static void rbd_header_free(struct rbd_i header->snap_sizes = NULL; kfree(header->snap_names); header->snap_names = NULL; - header->snap_names_len = 0; ceph_put_snap_context(header->snapc); header->snapc = NULL; } @@ -1800,7 +1801,6 @@ static int __rbd_refresh_header(struct r rbd_dev->header.total_snaps = h.total_snaps; rbd_dev->header.snapc = h.snapc; rbd_dev->header.snap_names = h.snap_names; - rbd_dev->header.snap_names_len = h.snap_names_len; rbd_dev->header.snap_sizes = h.snap_sizes; /* Free the extra copy of the object prefix */ WARN_ON(strcmp(rbd_dev->header.object_prefix, h.object_prefix));