linux/drivers/block/loop.c, branch v4.15

loop: fix concurrent lo_open/lo_release

2018-01-06T16:32:07Z

范龙飞 reports that KASAN can report a use-after-free in __lock_acquire. The reason is due to insufficient serialization in lo_release(), which will continue to use the loop device even after it has decremented the lo_refcnt to zero. In the meantime, another process can come in, open the loop device again as it is being shut down. Confusion ensues. Reported-by: 范龙飞 Signed-off-by: Linus Torvalds Signed-off-by: Jens Axboe

block: fix a build error

2017-09-26T18:07:24Z

The code is only for blkcg not for all cgroups Fixes: d4478e92d618 ("block/loop: make loop cgroup aware") Reported-by: kbuild test robot Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

block/loop: make loop cgroup aware

2017-09-26T13:41:22Z

loop block device handles IO in a separate thread. The actual IO dispatched isn't cloned from the IO loop device received, so the dispatched IO loses the cgroup context. I'm ignoring buffer IO case now, which is quite complicated. Making the loop thread aware cgroup context doesn't really help. The loop device only writes to a single file. In current writeback cgroup implementation, the file can only belong to one cgroup. For direct IO case, we could workaround the issue in theory. For example, say we assign cgroup1 5M/s BW for loop device and cgroup2 10M/s. We can create a special cgroup for loop thread and assign at least 15M/s for the underlayer disk. In this way, we correctly throttle the two cgroups. But this is tricky to setup. This patch tries to address the issue. We record bio's css in loop command. When loop thread is handling the command, we then use the API provided in patch 1 to set the css for current task. The bio layer will use the css for new IO (from patch 3). Acked-by: Tejun Heo Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

loop: set physical block size to logical block size

2017-09-06T17:08:49Z

Commit 6c6b6f28b333 ("loop: set physical block size to PAGE_SIZE") caused mkfs.xfs to barf on ppc64 [1]. Always using PAGE_SIZE as the physical block size still makes the most sense semantically, but let's just lie and always set it to the same value as the logical block size (same goes for io_min). In the future we might want to at least bump up io_min to PAGE_SIZE but I'm sick of these stupid changes so let's play it safe. 1: https://marc.info/?l=linux-xfs&m=150459024723753&w=2 Tested-by: Chandan Rajendra Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe

block/loop: fix use after free

2017-09-01T19:57:33Z

lo_rw_aio->call_read_iter-> 1 aops->direct_IO 2 iov_iter_revert lo_rw_aio_complete could happen between 1 and 2, the bio and bvec could be freed before 2, which accesses bvec. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

block/loop: allow request merge for directio mode

2017-09-01T14:44:34Z

Currently loop disables merge. While it makes sense for buffer IO mode, directio mode can benefit from request merge. Without merge, loop could send small size IO to underlayer disk and harm performance. Reviewed-by: Omar Sandoval Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

block/loop: set hw_sectors

2017-09-01T14:44:32Z

Loop can handle any size of request. Limiting it to 255 sectors just burns the CPU for bio split and request merge for underlayer disk and also cause bad fs block allocation in directio mode. Reviewed-by: Omar Sandoval Reviewed-by: Ming Lei Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

loop: fold loop_switch() into callers

2017-08-31T19:51:16Z

The comments here are really outdated, and blk-mq made flushing much simpler, so just fold the two cases into the callers. Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe

loop: add ioctl for changing logical block size

2017-08-31T19:51:14Z

This is a different approach from the first attempt in f2c6df7dbf9a ("loop: support 4k physical blocksize"). Rather than extending LOOP_{GET,SET}_STATUS, add a separate ioctl just for setting the block size. Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe

loop: set physical block size to PAGE_SIZE

2017-08-31T19:51:12Z

The physical block size is "the lowest possible sector size that the hardware can operate on without reverting to read-modify-write operations" (from the comment on blk_queue_physical_block_size()). Since loop does buffered I/O on the backing file by default, the RMW unit is a page. This isn't the case for direct I/O mode, but let's keep it simple. Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe