@@ -511,8 +511,9 @@ static int __begin_transaction_flags(struct dm_cache_metadata *cmd,
disk_super = dm_block_data(sblock);
update_flags(disk_super, mutator);
read_superblock_fields(cmd, disk_super);
+ dm_bm_unlock(sblock);
- return dm_bm_flush_and_unlock(cmd->bm, sblock);
+ return dm_bm_flush(cmd->bm);
}
static int __begin_transaction(struct dm_cache_metadata *cmd)
@@ -595,25 +595,14 @@ int dm_bm_unlock(struct dm_block *b)
}
EXPORT_SYMBOL_GPL(dm_bm_unlock);
-int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
- struct dm_block *superblock)
+int dm_bm_flush(struct dm_block_manager *bm)
{
- int r;
-
if (bm->read_only)
return -EPERM;
- r = dm_bufio_write_dirty_buffers(bm->bufio);
- if (unlikely(r)) {
- dm_bm_unlock(superblock);
- return r;
- }
-
- dm_bm_unlock(superblock);
-
return dm_bufio_write_dirty_buffers(bm->bufio);
}
-EXPORT_SYMBOL_GPL(dm_bm_flush_and_unlock);
+EXPORT_SYMBOL_GPL(dm_bm_flush);
void dm_bm_set_read_only(struct dm_block_manager *bm)
{
@@ -105,8 +105,7 @@ int dm_bm_unlock(struct dm_block *b);
*
* This method always blocks.
*/
-int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
- struct dm_block *superblock);
+int dm_bm_flush(struct dm_block_manager *bm);
/*
* Switches the bm to a read only mode. Once read-only mode
@@ -154,7 +154,7 @@ int dm_tm_pre_commit(struct dm_transaction_manager *tm)
if (r < 0)
return r;
- return 0;
+ return dm_bm_flush(tm->bm);
}
EXPORT_SYMBOL_GPL(dm_tm_pre_commit);
@@ -164,8 +164,9 @@ int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root)
return -EWOULDBLOCK;
wipe_shadow_table(tm);
+ dm_bm_unlock(root);
- return dm_bm_flush_and_unlock(tm->bm, root);
+ return dm_bm_flush(tm->bm);
}
EXPORT_SYMBOL_GPL(dm_tm_commit);
@@ -38,18 +38,17 @@ struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transac
/*
* We use a 2-phase commit here.
*
- * i) In the first phase the block manager is told to start flushing, and
- * the changes to the space map are written to disk. You should interrogate
- * your particular space map to get detail of its root node etc. to be
- * included in your superblock.
+ * i) Make all changes for the transaction *except* for the superblock.
+ * Then call dm_tm_pre_commit() to flush them to disk.
*
- * ii) @root will be committed last. You shouldn't use more than the
- * first 512 bytes of @root if you wish the transaction to survive a power
- * failure. You *must* have a write lock held on @root for both stage (i)
- * and (ii). The commit will drop the write lock.
+ * ii) Lock your superblock. Update. Then call dm_tm_commit() which will
+ * unlock the superblock and flush it. No other blocks should be updated
+ * during this period. Care should be taken to never unlock a partially
+ * updated superblock; perform any operations that could fail *before* you
+ * take the superblock lock.
*/
int dm_tm_pre_commit(struct dm_transaction_manager *tm);
-int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root);
+int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *superblock);
/*
* These methods are the only way to get hold of a writeable block.
This is a note to let you know that I have just added a patch titled dm transaction manager: fix corruption due to non-atomic transaction commit to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From c6336e8da5268e518b689cd0d19dbeef936ef3ea Mon Sep 17 00:00:00 2001 From: Joe Thornber <ejt@redhat.com> Date: Thu, 27 Mar 2014 14:13:20 +0000 Subject: dm transaction manager: fix corruption due to non-atomic transaction commit commit a9d45396f5956d0b615c7ae3b936afd888351a47 upstream. The persistent-data library used by dm-thin, dm-cache, etc is transactional. If anything goes wrong, such as an io error when writing new metadata or a power failure, then we roll back to the last transaction. Atomicity when committing a transaction is achieved by: a) Never overwriting data from the previous transaction. b) Writing the superblock last, after all other metadata has hit the disk. This commit and the following commit ("dm: take care to copy the space map roots before locking the superblock") fix a bug associated with (b). When committing it was possible for the superblock to still be written in spite of an io error occurring during the preceeding metadata flush. With these commits we're careful not to take the write lock out on the superblock until after the metadata flush has completed. Change the transaction manager's semantics for dm_tm_commit() to assume all data has been flushed _before_ the single superblock that is passed in. As a prerequisite, split the block manager's block unlocking and flushing by simplifying dm_bm_flush_and_unlock() to dm_bm_flush(). Now the unlocking must be done separately. This issue was discovered by forcing io errors at the crucial time using dm-flakey. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/md/dm-cache-metadata.c | 3 ++- drivers/md/persistent-data/dm-block-manager.c | 15 ++------------- drivers/md/persistent-data/dm-block-manager.h | 3 +-- drivers/md/persistent-data/dm-transaction-manager.c | 5 +++-- drivers/md/persistent-data/dm-transaction-manager.h | 17 ++++++++--------- 5 files changed, 16 insertions(+), 27 deletions(-) -- 1.9.1