From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2CB383D5647; Wed, 20 May 2026 18:33:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779301990; cv=none; b=nVHeKhGmvAOsh467PBzxPlX8B+kqclRR4gbU8g+04T5De5xd7ya/WzWoZe9nLemfcdi4eItcdu5mBVDcnlTj0JFHE9phzv5tijIsDpC6KVIShQacOLQRRS8sB+dAJNI3LG7AgouwDPld5P26PugAvxYd7OFS23AGX12D9773x+A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779301990; c=relaxed/simple; bh=gXpQGaHOpay4vOSdXWPbS/YA3sdKxLYc+FCRrGaVfIM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RH7PyXiZ1yeMu+wG/rweHShh/13q/Jlo//6IVZlY8pbxXz50pgOLkXOltlN/GHtXXbuKZM9PlQiAKPwtMRFgDhmykp1Tum5fK6/6q/jNQ2OgYu4YLIfmEQXgvJIPA8wxc8HvlA/ehrWAEbBSOFa4HvEL248vfg/sRTEG53Tob/Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EeK8g6DW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EeK8g6DW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DD911F000E9; Wed, 20 May 2026 18:33:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779301987; bh=cZg4PS7CaK7yMfe9E1iohtk1moeVVVFn1r7pdYSp+XY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EeK8g6DW/1CY2LRNqoi/fA6ZSzmpG8lnzQ93+F7RmsXchWLiLWj+ZIyVSt5z8d2KW kbhhrlURpnNG5F5Qh/SzWLABjTcMuspJzs3XbwHky3o6Es/BBazrSmADSNNAOtOTeH umuIujvMs5TJis42tFniv/ybLrt6yTmk6vwNA3Ks= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ming-Hung Tsai , Mikulas Patocka , Sasha Levin Subject: [PATCH 6.6 096/508] dm cache: support shrinking the origin device Date: Wed, 20 May 2026 18:18:39 +0200 Message-ID: <20260520162100.695503468@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162058.573354582@linuxfoundation.org> References: <20260520162058.573354582@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming-Hung Tsai [ Upstream commit c2662b1544cbd8ea3181381bb899b8e681dfedc7 ] This patch introduces formal support for shrinking the cache origin by reducing the cache target length via table reloads. Cache blocks mapped beyond the new target length must be clean and are invalidated during preresume. If any dirty blocks exist in the area being removed, the preresume operation fails without setting the NEEDS_CHECK flag in superblock, and the resume ioctl returns EFBIG. The cache device remains suspended until a table reload with target length that fits existing mappings is performed. Without this patch, reducing the cache target length could result in io errors (RHBZ: 2134334), out-of-bounds memory access to the discard bitset, and security concerns regarding data leakage. Verification steps: 1. create a cache metadata with some cached blocks mapped to the tail of the origin device. Here we use cache_restore v1.0 to build a metadata with one clean block mapped to the last origin block. cat <> cmeta.xml EOF dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2 dmsetup remove cmeta 2. bring up the cache whilst shrinking the cache origin by one block: dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524160 linear /dev/sdc 262144" dmsetup create cache --table "0 524160 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 3. check the number of cached data blocks via dmsetup status. It is expected to be zero. dmsetup status cache | cut -d ' ' -f 7 In addition to the script above, this patch can be verified using the "cache/resize" tests in dmtest-python: ./dmtest run --rx cache/resize/shrink_origin --result-set default Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Stable-dep-of: 322586745bd1 ("dm cache: fix dirty mapping checking in passthrough mode switching") Signed-off-by: Sasha Levin --- drivers/md/dm-cache-target.c | 72 ++++++++++++++++++++++++++++++++++-- 1 file changed, 69 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 65ae94f64c11b..77953a171860e 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -407,6 +407,12 @@ struct cache { mempool_t migration_pool; struct bio_set bs; + + /* + * Cache_size entries. Set bits indicate blocks mapped beyond the + * target length, which are marked for invalidation. + */ + unsigned long *invalid_bitset; }; struct per_bio_data { @@ -1958,6 +1964,9 @@ static void __destroy(struct cache *cache) if (cache->discard_bitset) free_bitset(cache->discard_bitset); + if (cache->invalid_bitset) + free_bitset(cache->invalid_bitset); + if (cache->copier) dm_kcopyd_client_destroy(cache->copier); @@ -2546,6 +2555,13 @@ static int cache_create(struct cache_args *ca, struct cache **result) } clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks)); + cache->invalid_bitset = alloc_bitset(from_cblock(cache->cache_size)); + if (!cache->invalid_bitset) { + *error = "could not allocate bitset for invalid blocks"; + goto bad; + } + clear_bitset(cache->invalid_bitset, from_cblock(cache->cache_size)); + cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle); if (IS_ERR(cache->copier)) { *error = "could not create kcopyd client"; @@ -2844,6 +2860,24 @@ static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock, return policy_load_mapping(cache->policy, oblock, cblock, dirty, hint, hint_valid); } +static int load_filtered_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock, + bool dirty, uint32_t hint, bool hint_valid) +{ + struct cache *cache = context; + + if (from_oblock(oblock) >= from_oblock(cache->origin_blocks)) { + if (dirty) { + DMERR("%s: unable to shrink origin; cache block %u is dirty", + cache_device_name(cache), from_cblock(cblock)); + return -EFBIG; + } + set_bit(from_cblock(cblock), cache->invalid_bitset); + return 0; + } + + return load_mapping(context, oblock, cblock, dirty, hint, hint_valid); +} + /* * The discard block size in the on disk metadata is not * necessarily the same as we're currently using. So we have to @@ -2998,6 +3032,24 @@ static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size) return 0; } +static int truncate_oblocks(struct cache *cache) +{ + uint32_t nr_blocks = from_cblock(cache->cache_size); + uint32_t i; + int r; + + for_each_set_bit(i, cache->invalid_bitset, nr_blocks) { + r = dm_cache_remove_mapping(cache->cmd, to_cblock(i)); + if (r) { + DMERR_LIMIT("%s: invalidation failed; couldn't update on disk metadata", + cache_device_name(cache)); + return r; + } + } + + return 0; +} + static int cache_preresume(struct dm_target *ti) { int r = 0; @@ -3022,11 +3074,25 @@ static int cache_preresume(struct dm_target *ti) } if (!cache->loaded_mappings) { + /* + * The fast device could have been resized since the last + * failed preresume attempt. To be safe we start by a blank + * bitset for cache blocks. + */ + clear_bitset(cache->invalid_bitset, from_cblock(cache->cache_size)); + r = dm_cache_load_mappings(cache->cmd, cache->policy, - load_mapping, cache); + load_filtered_mapping, cache); if (r) { DMERR("%s: could not load cache mappings", cache_device_name(cache)); - metadata_operation_failed(cache, "dm_cache_load_mappings", r); + if (r != -EFBIG) + metadata_operation_failed(cache, "dm_cache_load_mappings", r); + return r; + } + + r = truncate_oblocks(cache); + if (r) { + metadata_operation_failed(cache, "dm_cache_remove_mapping", r); return r; } @@ -3492,7 +3558,7 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits) static struct target_type cache_target = { .name = "cache", - .version = {2, 2, 0}, + .version = {2, 3, 0}, .module = THIS_MODULE, .ctr = cache_ctr, .dtr = cache_dtr, -- 2.53.0