kernel.git/drivers/md/bcache/super.c, branch linux-5.8.y

bcache: avoid nr_stripes overflow in bcache_device_init()

2020-08-21T11:14:56Z

commit 65f0f017e7be8c70330372df23bcb2a407ecf02d upstream. For some block devices which large capacity (e.g. 8TB) but small io_opt size (e.g. 8 sectors), in bcache_device_init() the stripes number calcu- lated by, DIV_ROUND_UP_ULL(sectors, d->stripe_size); might be overflow to the unsigned int bcache_device->nr_stripes. This patch uses the uint64_t variable to store DIV_ROUND_UP_ULL() and after the value is checked to be available in unsigned int range, sets it to bache_device->nr_stripes. Then the overflow is avoided. Reported-and-tested-by: Ken Raeburn Signed-off-by: Coly Li Cc: stable@vger.kernel.org Link: https://bugzilla.redhat.com/show_bug.cgi?id=1783075 Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: allocate meta data pages as compound pages

2020-08-21T11:14:56Z

commit 5fe48867856367142d91a82f2cbf7a57a24cbb70 upstream. There are some meta data of bcache are allocated by multiple pages, and they are used as bio bv_page for I/Os to the cache device. for example cache_set->uuids, cache->disk_buckets, journal_write->data, bset_tree->data. For such meta data memory, all the allocated pages should be treated as a single memory block. Then the memory management and underlying I/O code can treat them more clearly. This patch adds __GFP_COMP flag to all the location allocating >0 order pages for the above mentioned meta data. Then their pages are treated as compound pages now. Signed-off-by: Coly Li Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: fix super block seq numbers comparision in register_cache_set()

2020-08-19T06:26:22Z

[ Upstream commit 117f636ea695270fe492d0c0c9dfadc7a662af47 ] In register_cache_set(), c is pointer to struct cache_set, and ca is pointer to struct cache, if ca->sb.seq > c->sb.seq, it means this registering cache has up to date version and other members, the in- memory version and other members should be updated to the newer value. But current implementation makes a cache set only has a single cache device, so the above assumption works well except for a special case. The execption is when a cache device new created and both ca->sb.seq and c->sb.seq are 0, because the super block is never flushed out yet. In the location for the following if() check, 2156 if (ca->sb.seq > c->sb.seq) { 2157 c->sb.version = ca->sb.version; 2158 memcpy(c->sb.set_uuid, ca->sb.set_uuid, 16); 2159 c->sb.flags = ca->sb.flags; 2160 c->sb.seq = ca->sb.seq; 2161 pr_debug("set version = %llu\n", c->sb.version); 2162 } c->sb.version is not initialized yet and valued 0. When ca->sb.seq is 0, the if() check will fail (because both values are 0), and the cache set version, set_uuid, flags and seq won't be updated. The above problem is hiden for current code, because the bucket size is compatible among different super block version. And the next time when running cache set again, ca->sb.seq will be larger than 0 and cache set super block version will be updated properly. But if the large bucket feature is enabled, sb->bucket_size is the low 16bits of the bucket size. For a power of 2 value, when the actual bucket size exceeds 16bit width, sb->bucket_size will always be 0. Then read_super_common() will fail because the if() check to is_power_of_2(sb->bucket_size) is false. This is how the long time hidden bug is triggered. This patch modifies the if() check to the following way, 2156 if (ca->sb.seq > c->sb.seq || c->sb.seq == 0) { Then cache set's version, set_uuid, flags and seq will always be updated corectly including for a new created cache device. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: pr_info() format clean up in bcache_device_init()

2020-06-14T22:47:56Z

scripts/checkpatch.pl reports following warning for patch ("bcache: check and adjust logical block size for backing devices"), WARNING: quoted string split across lines #146: FILE: drivers/md/bcache/super.c:896: + pr_info("%s: sb/logical block size (%u) greater than page size " + "(%lu) falling back to device logical block size (%u)", There are two things to fix up, - The kernel message print should be in a single line. - pr_info() won't automatically add new line since v5.8, a '\n' should be added. This patch just does the above cleanup in bcache_device_init(). Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: use delayed kworker fo asynchronous devices registration

2020-06-14T22:47:56Z

This patch changes the asynchronous registration kworker to a delayed kworker. There is probability queue_work() queues the async registration kworker to the same CPU (even though very little), then the process which writing sysfs interface to reigster bcache device may won't return immeidately. queue_delayed_work() in this patch will delay 10 jiffies before insert the kworker to run queue, which makes sure the registering process may always returns to user space in time. Fixes: 9e23ccf8f0a22 ("bcache: asynchronous devices registration") Signed-off-by: Coly Li Cc: Hannes Reinecke Signed-off-by: Jens Axboe

bcache: check and adjust logical block size for backing devices

2020-06-14T22:47:56Z

It's possible for a block driver to set logical block size to a value greater than page size incorrectly; e.g. bcache takes the value from the superblock, set by the user w/ make-bcache. This causes a BUG/NULL pointer dereference in the path: __blkdev_get() -> set_init_blocksize() // set i_blkbits based on ... -> bdev_logical_block_size() -> queue_logical_block_size() // ... this value -> bdev_disk_changed() ... -> blkdev_readpage() -> block_read_full_page() -> create_page_buffers() // size = 1 << i_blkbits -> create_empty_buffers() // give size/take pointer -> alloc_page_buffers() // return NULL .. BUG! Because alloc_page_buffers() is called with size > PAGE_SIZE, thus it initializes head = NULL, skips the loop, return head; then create_empty_buffers() gets (and uses) the NULL pointer. This has been around longer than commit ad6bf88a6c19 ("block: fix an integer overflow in logical block size"); however, it increased the range of values that can trigger the issue. Previously only 8k/16k/32k (on x86/4k page size) would do it, as greater values overflow unsigned short to zero, and queue_ logical_block_size() would then use the default of 512. Now the range with unsigned int is much larger, and users w/ the 512k value, which happened to be zero'ed previously and work fine, started to hit this issue -- as the zero is gone, and queue_logical_block_size() does return 512k (>PAGE_SIZE.) Fix this by checking the bcache device's logical block size, and if it's greater than page size, fallback to the backing/ cached device's logical page size. This doesn't affect cache devices as those are still checked for block/page size in read_super(); only the backing/cached devices are not. Apparently it's a regression from commit 2903381fce71 ("bcache: Take data offset from the bdev superblock."), moving the check into BCACHE_SB_VERSION_CDEV only. Now that we have superblocks of backing devices out there with this larger value, we cannot refuse to load them (i.e., have a similar check in _BDEV.) Ideally perhaps bcache should use all values from the backing device (physical/logical/io_min block size)? But for now just fix the problematic case. Test-case: # IMG=/root/disk.img # dd if=/dev/zero of=$IMG bs=1 count=0 seek=1G # DEV=$(losetup --find --show $IMG) # make-bcache --bdev $DEV --block 8k < see dmesg > Before: # uname -r 5.7.0-rc7 [ 55.944046] BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 55.949742] CPU: 3 PID: 610 Comm: bcache-register Not tainted 5.7.0-rc7 #4 ... [ 55.952281] RIP: 0010:create_empty_buffers+0x1a/0x100 ... [ 55.966434] Call Trace: [ 55.967021] create_page_buffers+0x48/0x50 [ 55.967834] block_read_full_page+0x49/0x380 [ 55.972181] do_read_cache_page+0x494/0x610 [ 55.974780] read_part_sector+0x2d/0xaa [ 55.975558] read_lba+0x10e/0x1e0 [ 55.977904] efi_partition+0x120/0x5a6 [ 55.980227] blk_add_partitions+0x161/0x390 [ 55.982177] bdev_disk_changed+0x61/0xd0 [ 55.982961] __blkdev_get+0x350/0x490 [ 55.983715] __device_add_disk+0x318/0x480 [ 55.984539] bch_cached_dev_run+0xc5/0x270 [ 55.986010] register_bcache.cold+0x122/0x179 [ 55.987628] kernfs_fop_write+0xbc/0x1a0 [ 55.988416] vfs_write+0xb1/0x1a0 [ 55.989134] ksys_write+0x5a/0xd0 [ 55.989825] do_syscall_64+0x43/0x140 [ 55.990563] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 55.991519] RIP: 0033:0x7f7d60ba3154 ... After: # uname -r 5.7.0.bcachelbspgsz [ 31.672460] bcache: bcache_device_init() bcache0: sb/logical block size (8192) greater than page size (4096) falling back to device logical block size (512) [ 31.675133] bcache: register_bdev() registered backing device loop0 # grep ^ /sys/block/bcache0/queue/*_block_size /sys/block/bcache0/queue/logical_block_size:512 /sys/block/bcache0/queue/physical_block_size:8192 Reported-by: Ryan Finnie Reported-by: Sebastian Marsching Signed-off-by: Mauricio Faria de Oliveira Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: configure the asynchronous registertion to be experimental

2020-05-27T11:19:36Z

In order to avoid the experimental async registration interface to be treated as new kernel ABI for common users, this patch makes it as an experimental kernel configure BCACHE_ASYNC_REGISTRAION. This interface is for extreme large cached data situation, to make sure the bcache device can always created without the udev timeout issue. For normal users the async or sync registration does not make difference. In future when we decide to use the asynchronous registration as default behavior, this experimental interface may be removed. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: asynchronous devices registration

2020-05-27T11:19:36Z

When there is a lot of data cached on cache device, the bcach internal btree can take a very long to validate during the backing device and cache device registration. In my test, it may takes 55+ minutes to check all the internal btree nodes. The problem is that the registration is invoked by udev rules and the udevd has 180 seconds timeout by default. If the btree node checking time is longer than udevd timeout, the registering process will be killed by udevd with SIGKILL. If the registering process has pending sigal, creating kthread for bcache will fail and the device registration will fail. The result is, for bcache device which cached a lot of data on cache device, the bcache device node like /dev/bcache won't create always due to the very long btree checking time. A solution to avoid the udevd 180 seconds timeout is to register devices in an asynchronous way. Which is, after writing cache or backing device path into /sys/fs/bcache/register_async, the kernel code will create a kworker and move all the btree node checking (for cache device) or dirty data counting (for cached device) in the kwork context. Then the kworder is scheduled on system_wq and the registration code just returned to user space udev rule task. By this asynchronous way, the udev task for bcache rule will complete in seconds, no matter how long time spent in the kworker context, it won't be killed by udevd for a timeout. After all the checking and counting are done asynchronously in the kworker, the bcache device will eventually be created successfully. This patch does the above chagne and add a register sysfs file /sys/fs/bcache/register_async. Writing the registering device path into this sysfs file will do the asynchronous registration. The register_async interface is for very rare condition and won't be used for common users. In future I plan to make the asynchronous registration as default behavior, which depends on feedback for this patch. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: fix refcount underflow in bcache_device_free()

2020-05-27T11:19:36Z

The problematic code piece in bcache_device_free() is, 785 static void bcache_device_free(struct bcache_device *d) 786 { 787 struct gendisk *disk = d->disk; [snipped] 799 if (disk) { 800 if (disk->flags & GENHD_FL_UP) 801 del_gendisk(disk); 802 803 if (disk->queue) 804 blk_cleanup_queue(disk->queue); 805 806 ida_simple_remove(&bcache_device_idx, 807 first_minor_to_idx(disk->first_minor)); 808 put_disk(disk); 809 } [snipped] 816 } At line 808, put_disk(disk) may encounter kobject refcount of 'disk' being underflow. Here is how to reproduce the issue, - Attche the backing device to a cache device and do random write to make the cache being dirty. - Stop the bcache device while the cache device has dirty data of the backing device. - Only register the backing device back, NOT register cache device. - The bcache device node /dev/bcache0 won't show up, because backing device waits for the cache device shows up for the missing dirty data. - Now echo 1 into /sys/fs/bcache/pendings_cleanup, to stop the pending backing device. - After the pending backing device stopped, use 'dmesg' to check kernel message, a use-after-free warning from KASA reported the refcount of kobject linked to the 'disk' is underflow. The dropping refcount at line 808 in the above code piece is added by add_disk(d->disk) in bch_cached_dev_run(). But in the above condition the cache device is not registered, bch_cached_dev_run() has no chance to be called and the refcount is not added. The put_disk() for a non- added refcount of gendisk kobject triggers a underflow warning. This patch checks whether GENHD_FL_UP is set in disk->flags, if it is not set then the bcache device was not added, don't call put_disk() and the the underflow issue can be avoided. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: Convert pr_ uses to a more typical style

2020-05-27T11:19:36Z

Remove the trailing newline from the define of pr_fmt and add newlines to the uses. Miscellanea: o Convert bch_bkey_dump from multiple uses of pr_err to pr_cont as the earlier conversion was inappropriate done causing multiple lines to be emitted where only a single output line was desired o Use vsprintf extension %pV in bch_cache_set_error to avoid multiple line output where only a single line output was desired o Coalesce formats Fixes: 6ae63e3501c4 ("bcache: replace printk() by pr_*() routines") Signed-off-by: Joe Perches Signed-off-by: Coly Li Signed-off-by: Jens Axboe