kernel.git/drivers/md/dm-bufio.c, branch linux-4.18.y

dm bufio: fix buffer alignment

2018-04-30T15:51:39Z

Commit 6b5e718cc138 ("dm bufio: relax alignment constraint on slab cache") relaxed alignment on dm-bufio cache, however it may break dm-crypt or dm-integrity. dm-crypt and dm-integrity require that the size of bio vector entries (bv_len) is aligned on its sector size. bv_offset doesn't have to be aligned, but bv_len must be. XFS sends unaligned bios, but they do not cross page boundary, so the requirement for aligned bv_len is met. Commit 6b5e718cc138 made dm-bufio send unaligned bios that cross page boundary, this could break dm-crypt and dm-integrity. Reinstates the alignment. Note that misaligned entries only happen when we use slab/slub debugging. Without debugging, the entries are always aligned. Fixes: 6b5e718cc138 ("dm bufio: relax alignment constraint on slab cache") Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: don't embed a bio in the dm_buffer structure

2018-04-03T19:04:29Z

The bio structure consumes a substantial part of dm_buffer. The bio structure is only needed when doing I/O on the buffer, thus we don't have to embed it in the buffer. Allocate the bio structure only when doing I/O. We don't need to create a bio_set because, in case of allocation failure, dm-bufio falls back to using dm-io (which keeps its own bio_set). Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: support non-power-of-two block sizes

2018-04-03T19:04:28Z

Support block sizes that are not a power-of-two (but they must be a multiple of 512b). As always, a slab cache is used for allocations. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: use slab cache for dm_buffer structure allocations

2018-04-03T19:04:27Z

kmalloc padded to the next power of two, using a slab cache avoids this. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: reorder fields in dm_buffer structure

2018-04-03T19:04:26Z

Reorder fields in dm_buffer structure to improve packing and reduce structure size. The compiler allocates 32-bit integer for field 'enum data_mode', so change it to unsigned char. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: relax alignment constraint on slab cache

2018-04-03T19:04:25Z

The I/O buffer doesn't have to be aligned on block size granularity, relax alignment to ARCH_KMALLOC_MINALIGN (required to allow DMA from slab cache memory on some architectures). Also, set SLAB_RECLAIM_ACCOUNT so that the memory allocated from the cache is accounted as reclaimable and doesn't inflate the 'used' entry in the free command. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: remove code that merges slab caches

2018-04-03T19:04:25Z

All slab allocators can merge duplicate caches. So dm-bufio doesn't need extra slab merging logic. Instead it can just allocate one slab cache per client and let the allocator merge them. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: get rid of slab cache name allocations

2018-04-03T19:04:24Z

dm-bufio keeps the dm_bufio_cache_names array that holds names of the slab caches. Since the commit db265eca7700 ("mm/sl[aou]b: Move duping of slab name to slab_common.c"), the kernel automatically duplicates the slab cache name when creating the slab cache, so we no longer have to keep the name allocated. Remove the code that allocates the slab names and keeps them around. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: move dm-bufio.h to include/linux/

2018-04-03T19:04:23Z

Move dm-bufio.h to include/linux/ so that external GPL'd DM target modules can use it. It is better to allow the use of dm-bufio than force external modules to implement the equivalent buffered IO mechanism in some new way. The hope is this will encourage the use of dm-bufio; which will then make it easier for a GPL'd external DM target module to be included upstream. A couple dm-bufio EXPORT_SYMBOL exports have also been updated to use EXPORT_SYMBOL_GPL. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm bufio: delete outdated comment

2018-04-03T19:04:22Z

This comment was true when dm-bufio was written but, since 4.3, bios can now have arbitrary size and the driver splits them. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer