kernel/linux.git/drivers/md/dm-snap.c, branch v2.6.32

dm snapshot: use unsigned integer chunk size

2009-10-16T22:18:17+00:00

Use unsigned integer chunk size. Maximum chunk size is 512kB, there won't ever be need to use 4GB chunk size, so the number can be 32-bit. This fixes compiler failure on 32-bit systems with large block devices. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Reviewed-by: Jonathan Brassow Signed-off-by: Alasdair G Kergon

dm snapshot: lock snapshot while supplying status

2009-10-16T22:18:16+00:00

This patch locks the snapshot when returning status. It fixes a race when it could return an invalid number of free chunks if someone was simultaneously modifying it. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm snapshot: require non zero chunk size by end of ctr

2009-10-16T22:18:16+00:00

If we are creating snapshot with memory-stored exception store, fail if the user didn't specify chunk size. Zero chunk size would probably crash a lot of places in the rest of snapshot code. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Reviewed-by: Jonathan Brassow Reviewed-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm snapshot: free exception store on init failure

2009-10-16T22:18:14+00:00

While initializing the snapshot module, if we fail to register the snapshot target then we must back-out the exception store module initialization. Cc: stable@kernel.org Signed-off-by: Jonathan Brassow Reviewed-by: Mikulas Patocka Reviewed-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm snapshot: sort by chunk size to fix race

2009-10-16T22:18:14+00:00

Avoid a race causing corruption when snapshots of the same origin have different chunk sizes by sorting the internal list of snapshots by chunk size, largest first. https://bugzilla.redhat.com/show_bug.cgi?id=182659 For example, let's have two snapshots with different chunk sizes. The first snapshot (1) has small chunk size and the second snapshot (2) has large chunk size. Let's have chunks A, B, C in these snapshots: snapshot1: ====A==== ====B==== snapshot2: ==========C========== (Chunk size is a power of 2. Chunks are aligned.) A write to the origin at a position within A and C comes along. It triggers reallocation of A, then reallocation of C and links them together using A as the 'primary' exception. Then another write to the origin comes along at a position within B and C. It creates pending exception for B. C already has a reallocation in progress and it already has a primary exception (A), so nothing is done to it: B and C are not linked. If the reallocation of B finishes before the reallocation of C, because there is no link with the pending exception for C it does not know to wait for it and, the second write is dispatched to the origin and causes data corruption in the chunk C in snapshot2. To avoid this situation, we maintain snapshots sorted in descending order of chunk size. This leads to a guaranteed ordering on the links between the pending exceptions and avoids the problem explained above - both A and B now get linked to C. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

dm snapshot: implement iterate devices

2009-09-04T19:40:19+00:00

Implement the .iterate_devices for the origin and snapshot targets. dm-snapshot's lack of .iterate_devices resulted in the inability to properly establish queue_limits for both targets. With 4K sector drives: an unfortunate side-effect of not establishing proper limits in either targets' DM device was that IO to the devices would fail even though both had been created without error. Commit af4874e03ed82f050d5872d8c39ce64bf16b5c38 ("dm target:s introduce iterate devices fn") in 2.6.31-rc1 should have implemented .iterate_devices for dm-snap.c's origin and snapshot targets. Signed-off-by: Mike Snitzer Signed-off-by: Andrew Morton Signed-off-by: Alasdair G Kergon

dm snapshot: support barriers

2009-06-22T09:12:25+00:00

Flush support for dm-snapshot target. This patch just forwards the flush request to either the origin or the snapshot device. (It doesn't flush exception store metadata.) Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon

block: move bio list helpers into bio.h

2009-04-15T06:28:09+00:00

It's used by DM and MD and generally useful, so move the bio list helpers into bio.h. Signed-off-by: Christoph Hellwig Acked-by: Alasdair G Kergon Signed-off-by: Jens Axboe

dm snapshot: move status to exception store

2009-04-02T18:55:35+00:00

Let the exception store types print out their status through the new API, rather than having the snapshot code do it. Adjust the buffer position to allow for the preceding DMEMIT in the arguments to type->status(). Signed-off-by: Jonathan Brassow Signed-off-by: Alasdair G Kergon

dm snapshot: move ctr parsing to exception store

2009-04-02T18:55:34+00:00

First step of having the exception stores parse their own arguments - generalizing the interface. Signed-off-by: Jonathan Brassow Signed-off-by: Alasdair G Kergon