kernel/linux.git/drivers/md/dm-snap.c, branch v3.4.84

dm: fix truncated status strings

2013-12-08T15:29:43+00:00

commit fd7c092e711ebab55b2688d3859d95dfd0301f73 upstream. Avoid returning a truncated table or status string instead of setting the DM_BUFFER_FULL_FLAG when the last target of a table fills the buffer. When processing a table or status request, the function retrieve_status calls ti->type->status. If ti->type->status returns non-zero, retrieve_status assumes that the buffer overflowed and sets DM_BUFFER_FULL_FLAG. However, targets don't return non-zero values from their status method on overflow. Most targets returns always zero. If a buffer overflow happens in a target that is not the last in the table, it gets noticed during the next iteration of the loop in retrieve_status; but if a buffer overflow happens in the last target, it goes unnoticed and erroneously truncated data is returned. In the current code, the targets behave in the following way: * dm-crypt returns -ENOMEM if there is not enough space to store the key, but it returns 0 on all other overflows. * dm-thin returns errors from the status method if a disk error happened. This is incorrect because retrieve_status doesn't check the error code, it assumes that all non-zero values mean buffer overflow. * all the other targets always return 0. This patch changes the ti->type->status function to return void (because most targets don't use the return code). Overflow is detected in retrieve_status: if the status method fills up the remaining space completely, it is assumed that buffer overflow happened. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman

dm-snapshot: fix performance degradation due to small hash size

2013-10-05T14:06:54+00:00

commit 60e356f381954d79088d0455e357db48cfdd6857 upstream. LVM2, since version 2.02.96, creates origin with zero size, then loads the snapshot driver and then loads the origin. Consequently, the snapshot driver sees the origin size zero and sets the hash size to the lower bound 64. Such small hash table causes performance degradation. This patch changes it so that the hash size is determined by the size of snapshot volume, not minimum of origin and snapshot size. It doesn't make sense to set the snapshot size significantly larger than the origin size, so we do not need to take origin size into account when calculating the hash size. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm snapshot: fix error return code in snapshot_ctr

2013-05-19T17:54:37+00:00

commit 09e8b813897a0f85bb401435d009228644c81214 upstream. Return -ENOMEM instead of success if unable to allocate pending exception mempool in snapshot_ctr. Signed-off-by: Wei Yongjun Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman

dm snapshot: skip reading origin when overwriting complete chunk

2011-08-02T11:32:04+00:00

If we write a full chunk in the snapshot, skip reading the origin device because the whole chunk will be overwritten anyway. This patch changes the snapshot write logic when a full chunk is written. In this case: 1. allocate the exception 2. dispatch the bio (but don't report the bio completion to device mapper) 3. write the exception record 4. report bio completed Callbacks must be done through the kcopyd thread, because callbacks must not race with each other. So we create two new functions: dm_kcopyd_prepare_callback: allocate a job structure and prepare the callback. (This function must not be called from interrupt context.) dm_kcopyd_do_callback: submit callback. (This function may be called from interrupt context.) Performance test (on snapshots with 4k chunk size): without the patch: non-direct-io sequential write (dd): 17.7MB/s direct-io sequential write (dd): 20.9MB/s non-direct-io random write (mkfs.ext2): 0.44s with the patch: non-direct-io sequential write (dd): 26.5MB/s direct-io sequential write (dd): 33.2MB/s non-direct-io random write (mkfs.ext2): 0.27s Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm snapshot: style cleanups

2011-08-02T11:32:03+00:00

Coding style cleanups. Signed-off-by: Alasdair G Kergon Signed-off-by: Jonathan Brassow

dm snapshot: remove unused definitions

2011-08-02T11:32:03+00:00

Remove a couple of unused #defines. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm kcopyd: return client directly and not through a pointer

2011-05-29T12:03:13+00:00

Return client directly from dm_kcopyd_client_create, not through a parameter, making it consistent with dm_io_client_create. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm kcopyd: reserve fewer pages

2011-05-29T12:03:11+00:00

Reserve just the minimum of pages needed to process one job. Because we allocate pages from page allocator, we don't need to reserve a large number of pages. The maximum job size is SUB_JOB_SIZE and we calculate the number of reserved pages based on this. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm: fix opening log and cow devices for read only tables

2011-03-24T13:52:14+00:00

If a table is read-only, also open any log and cow devices it uses read-only. Previously, even read-only devices were opened read-write internally. After patch 75f1dc0d076d1c1168f2115f1941ea627d38bd5a block: check bdev_read_only() from blkdev_get() was applied, loading such tables began to fail. The patch was reverted by e51900f7d38cbcfb481d84567fd92540e7e1d23a block: revert block_dev read-only check but this patch fixes this part of the code to work with the original patch. Signed-off-by: Milan Broz Signed-off-by: Alasdair G Kergon

dm snapshot: avoid storing private suspended state

2011-01-13T19:59:59+00:00

Use dm_suspended() rather than having each snapshot target maintain a private 'suspended' flag in struct dm_snapshot. Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon