From 4156d998409be065aa8141b6bd2c6f18be1b21e9 Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Thu, 2 Aug 2012 11:29:46 -0500 Subject: [PATCH] rbd: separate reading header from decoding it 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 Reviewed-by: Josh Durgin --- drivers/block/rbd.c | 136 ++++++++++++++++++++++++++++++---------------------- 1 file changed, 79 insertions(+), 57 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 5bcd4eb..8e6e29e 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -513,15 +513,11 @@ static bool rbd_dev_ondisk_valid(struct rbd_image_header_ondisk *ondisk) * 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); @@ -558,15 +554,6 @@ static int rbd_header_from_disk(struct rbd_image_header *header, 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); @@ -1629,61 +1616,96 @@ static void rbd_free_disk(struct rbd_device *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 NUL-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; - - rc = rbd_req_sync_read(rbd_dev, - CEPH_NOSNAP, + do { + size_t size; + + kfree(ondisk); + + 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((size_t) ret < size)) { + ret = -ENXIO; + pr_warning("short header read for image %s" + " (want %zd got %d)\n", + rbd_dev->image_name, size, ret); + goto out_err; + } + if (!rbd_dev_ondisk_valid(ondisk)) { + ret = -ENXIO; + pr_warning("invalid header for image %s\n", + rbd_dev->image_name); + 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); -out_dh: - kfree(dh); - return rc; + 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; + kfree(ondisk); + + return ret; } /* -- 2.7.4