From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42166) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VlCIg-0004Dy-S4 for qemu-devel@nongnu.org; Tue, 26 Nov 2013 01:39:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VlCIX-0000lI-JH for qemu-devel@nongnu.org; Tue, 26 Nov 2013 01:39:10 -0500 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:34243) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VlCIW-0000l2-QI for qemu-devel@nongnu.org; Tue, 26 Nov 2013 01:39:01 -0500 Received: from /spool/local by e23smtp08.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 26 Nov 2013 16:38:53 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id D1EE12BB0053 for ; Tue, 26 Nov 2013 17:38:50 +1100 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id rAQ6ccG12818380 for ; Tue, 26 Nov 2013 17:38:38 +1100 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id rAQ6cnnH017771 for ; Tue, 26 Nov 2013 17:38:50 +1100 From: Xu Wang Date: Tue, 26 Nov 2013 01:38:30 -0500 Message-Id: <1385447913-19004-2-git-send-email-gesaint@linux.vnet.ibm.com> In-Reply-To: <1385447913-19004-1-git-send-email-gesaint@linux.vnet.ibm.com> References: <1385447913-19004-1-git-send-email-gesaint@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH V9 1/4] block/qemu-img: Refine and export infinite loop checking in collect_image_info_list() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, stefanha@gmail.com, wdongxu@linux.vnet.ibm.com, Xu Wang If there is a loop in the backing file chain, it could cause problems such as no response or a segfault during system boot. Hence detecting a backing file loop is necessary. This patch extracts the loop check from collect_image_info_list() in block.c into independent functions bdrv_backing_chain_okay() and bdrv_image_create_okay(). Signed-off-by: Xu Wang --- block.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++ include/block/block.h | 3 +++ qemu-img.c | 52 ++++++++++++++++++------------------ 3 files changed, 102 insertions(+), 26 deletions(-) diff --git a/block.c b/block.c index 382ea71..7016ce8 100644 --- a/block.c +++ b/block.c @@ -4497,6 +4497,79 @@ bdrv_acct_done(BlockDriverState *bs, BlockAcctCookie *cookie) bs->total_time_ns[cookie->type] += get_clock() - cookie->start_time_ns; } +static bool file_chain_has_loop(GHashTable *filenames, const char *filename, + BlockDriver *drv, Error **errp) +{ + BlockDriverState *bs; + char fbuf[PATH_MAX]; + Error *local_err = NULL; + int ret; + + while (filename && (filename[0] != '\0')) { + if (g_hash_table_lookup_extended(filenames, filename, NULL, NULL)) { + error_setg(errp, "Backing file '%s' creates an infinite loop.", + filename); + return true; + } + g_hash_table_insert(filenames, (gpointer)filename, NULL); + + bs = bdrv_new("image"); + ret = bdrv_open(bs, filename, NULL, + BDRV_O_CACHE_WB | BDRV_O_NO_BACKING, drv, &local_err); + if (ret < 0) { + error_setg(errp, "Could not open '%s': %s", filename, + error_get_pretty(local_err)); + return true; + } + + bdrv_get_backing_filename(bs, fbuf, sizeof(fbuf)); + filename = fbuf; + drv = NULL; + + bdrv_unref(bs); + } + + return false; +} + +/** + * Check backing file chain if there is a loop in it. + * + * @filename: topmost image filename of backing file chain. + * @drv: topmost image driver(may be NULL to autodetect). + * @new_filename: if a new image to be created and takes @filename as backing + * file, the new chain should be checked before creating. + * + * Returns: true for backing chain okay, false for loop happened. + */ +bool bdrv_backing_chain_okay(const char *filename, BlockDriver *drv, + const char *new_filename, Error **errp) +{ + GHashTable *filenames; + + filenames = g_hash_table_new_full(g_str_hash, g_str_equal, NULL, NULL); + + if (filename == NULL || filename[0] == '\0') { + goto exit; + } + + if (new_filename && new_filename[0] != '\0') { + g_hash_table_insert(filenames, (gpointer)new_filename, NULL); + } + + if (file_chain_has_loop(filenames, filename, drv, errp)) { + goto err; + } + +exit: + g_hash_table_destroy(filenames); + return true; + +err: + g_hash_table_destroy(filenames); + return false; +} + void bdrv_img_create(const char *filename, const char *fmt, const char *base_filename, const char *base_fmt, char *options, uint64_t img_size, int flags, diff --git a/include/block/block.h b/include/block/block.h index 3560deb..f5e84dc 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -378,6 +378,9 @@ int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf, int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf, int64_t pos, int size); +bool bdrv_backing_chain_okay(const char *filename, BlockDriver *drv, + const char *new_filename, Error **errp); + void bdrv_img_create(const char *filename, const char *fmt, const char *base_filename, const char *base_fmt, char *options, uint64_t img_size, int flags, diff --git a/qemu-img.c b/qemu-img.c index b6b5644..1f38267 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -281,6 +281,14 @@ static BlockDriverState *bdrv_new_open(const char *filename, drv = NULL; } + /* check backing file loop if the whole chain need to be opened */ + if (!(flags & BDRV_O_NO_BACKING) && + !bdrv_backing_chain_okay(filename, drv, NULL, &local_err)) { + error_report("bdrv_new_open: Open %s failed: %s", filename, + error_get_pretty(local_err)); + goto fail; + } + ret = bdrv_open(bs, filename, NULL, flags, drv, &local_err); if (ret < 0) { error_report("Could not open '%s': %s", filename, @@ -1641,11 +1649,6 @@ static void dump_human_image_info_list(ImageInfoList *list) } } -static gboolean str_equal_func(gconstpointer a, gconstpointer b) -{ - return strcmp(a, b) == 0; -} - /** * Open an image file chain and return an ImageInfoList * @@ -1663,30 +1666,24 @@ static ImageInfoList *collect_image_info_list(const char *filename, bool chain) { ImageInfoList *head = NULL; + BlockDriverState *bs; + ImageInfoList *elem; ImageInfoList **last = &head; - GHashTable *filenames; + ImageInfo *info; Error *err = NULL; + int flags = BDRV_O_FLAGS; - filenames = g_hash_table_new_full(g_str_hash, str_equal_func, NULL, NULL); - - while (filename) { - BlockDriverState *bs; - ImageInfo *info; - ImageInfoList *elem; - - if (g_hash_table_lookup_extended(filenames, filename, NULL, NULL)) { - error_report("Backing file '%s' creates an infinite loop.", - filename); - goto err; - } - g_hash_table_insert(filenames, (gpointer)filename, NULL); + if (!chain) { + flags |= BDRV_O_NO_BACKING; + } - bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_NO_BACKING, - false, false); - if (!bs) { - goto err; - } + bs = bdrv_new_open(filename, fmt, flags, + false, false); + if (!bs) { + goto err; + } + while (filename) { bdrv_query_image_info(bs, &info, &err); if (error_is_set(&err)) { error_report("%s", error_get_pretty(err)); @@ -1711,14 +1708,17 @@ static ImageInfoList *collect_image_info_list(const char *filename, if (info->has_backing_filename_format) { fmt = info->backing_filename_format; } + + if (filename) { + bs = bdrv_find_backing_image(bs, filename); + } } } - g_hash_table_destroy(filenames); + return head; err: qapi_free_ImageInfoList(head); - g_hash_table_destroy(filenames); return NULL; } -- 1.8.1.4