From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 4/4] rbd: separate reading header from decoding it Date: Mon, 06 Aug 2012 11:17:58 -0700 Message-ID: <50200A56.90506@inktank.com> References: <502009D1.7090005@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pb0-f46.google.com ([209.85.160.46]:53282 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932114Ab2HFSSA (ORCPT ); Mon, 6 Aug 2012 14:18:00 -0400 Received: by mail-pb0-f46.google.com with SMTP id rr13so2921462pbb.19 for ; Mon, 06 Aug 2012 11:18:00 -0700 (PDT) In-Reply-To: <502009D1.7090005@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: "ceph-devel@vger.kernel.org" Right now rbd_read_header() both reads the header object for an rbd image and decodes its contents. It does this repeatedly if needed, in order to ensure a complete and intact header is obtained. Separate this process into two steps--reading of the raw header data (in new function, rbd_dev_v1_header_read()) and separately decoding its contents (in rbd_header_from_disk()). As a result, the latter function no longer requires its allocated_snaps argument. Signed-off-by: Alex Elder --- drivers/block/rbd.c | 132 +++++++++++++++++++++++++++++----------------------- 1 file changed, 76 insertions(+), 56 deletions(-) Index: b/drivers/block/rbd.c =================================================================== --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -514,15 +514,11 @@ static bool rbd_dev_ondisk_valid(struct * header. */ static int rbd_header_from_disk(struct rbd_image_header *header, - struct rbd_image_header_ondisk *ondisk, - u32 allocated_snaps) + struct rbd_image_header_ondisk *ondisk) { u32 snap_count; size_t size; - if (!rbd_dev_ondisk_valid(ondisk)) - return -ENXIO; - memset(header, 0, sizeof (*header)); snap_count = le32_to_cpu(ondisk->snap_count); @@ -559,15 +555,6 @@ static int rbd_header_from_disk(struct r header->comp_type = ondisk->options.comp_type; header->total_snaps = snap_count; - /* - * If the number of snapshot ids provided by the caller - * doesn't match the number in the entire context there's - * no point in going further. Caller will try again after - * getting an updated snapshot context from the server. - */ - if (allocated_snaps != snap_count) - return 0; - size = sizeof (struct ceph_snap_context); size += snap_count * sizeof (header->snapc->snaps[0]); header->snapc = kzalloc(size, GFP_KERNEL); @@ -1630,61 +1617,94 @@ static void rbd_free_disk(struct rbd_dev } /* - * reload the ondisk the header + * Read the complete header for the given rbd device. + * + * Returns a pointer to a dynamically-allocated buffer containing + * the complete and validated header. Caller can pass the address + * of a variable that will be filled in with the version of the + * header object at the time it was read. + * + * Returns a pointer-coded errno if a failure occurs. */ -static int rbd_read_header(struct rbd_device *rbd_dev, - struct rbd_image_header *header) +static struct rbd_image_header_ondisk * +rbd_dev_v1_header_read(struct rbd_device *rbd_dev, u64 *version) { - ssize_t rc; - struct rbd_image_header_ondisk *dh; + struct rbd_image_header_ondisk *ondisk = NULL; u32 snap_count = 0; - u64 ver; - size_t len; + u64 names_size = 0; + u32 want_count; + int ret; /* - * First reads the fixed-size header to determine the number - * of snapshots, then re-reads it, along with all snapshot - * records as well as their stored names. + * The complete header will include an array of its 64-bit + * snapshot ids, followed by the names of those snapshots as + * a contiguous block of null-terminated strings. Note that + * the number of snapshots could change by the time we read + * it in, in which case we re-read it. */ - len = sizeof (*dh); - while (1) { - dh = kmalloc(len, GFP_KERNEL); - if (!dh) - return -ENOMEM; + do { + size_t size; + + kfree(ondisk); - rc = rbd_req_sync_read(rbd_dev, - CEPH_NOSNAP, + size = sizeof (*ondisk); + size += snap_count * sizeof (struct rbd_image_snap_ondisk); + size += names_size; + ondisk = kmalloc(size, GFP_KERNEL); + if (!ondisk) + return ERR_PTR(-ENOMEM); + + ret = rbd_req_sync_read(rbd_dev, CEPH_NOSNAP, rbd_dev->header_name, - 0, len, - (char *)dh, &ver); - if (rc < 0) - goto out_dh; - - rc = rbd_header_from_disk(header, dh, snap_count); - if (rc < 0) { - if (rc == -ENXIO) - pr_warning("unrecognized header format" - " for image %s\n", - rbd_dev->image_name); - goto out_dh; + 0, size, + (char *) ondisk, version); + + if (ret < 0) + goto out_err; + if (WARN_ON(ret < size)) { + ret = -ENXIO; + goto out_err; + } + if (!rbd_dev_ondisk_valid(ondisk)) { + ret = -ENXIO; + goto out_err; } - if (snap_count == header->total_snaps) - break; + names_size = le64_to_cpu(ondisk->snap_names_len); + want_count = snap_count; + snap_count = le32_to_cpu(ondisk->snap_count); + } while (snap_count != want_count); - snap_count = header->total_snaps; - len = sizeof (*dh) + - snap_count * sizeof(struct rbd_image_snap_ondisk) + - header->snap_names_len; + return ondisk; - rbd_header_free(header); - kfree(dh); - } - header->obj_version = ver; +out_err: + kfree(ondisk); + + return ERR_PTR(ret); +} + +/* + * reload the ondisk the header + */ +static int rbd_read_header(struct rbd_device *rbd_dev, + struct rbd_image_header *header) +{ + struct rbd_image_header_ondisk *ondisk; + u64 ver = 0; + int ret; + + ondisk = rbd_dev_v1_header_read(rbd_dev, &ver); + if (IS_ERR(ondisk)) + return PTR_ERR(ondisk); + ret = rbd_header_from_disk(header, ondisk); + if (ret >= 0) + header->obj_version = ver; + else if (ret == -ENXIO) + pr_warning("unrecognized header format for image %s\n", + rbd_dev->image_name); + kfree(ondisk); -out_dh: - kfree(dh); - return rc; + return ret; } /*