kernel.git/fs/btrfs/transaction.c, branch linux-3.2.y

Btrfs: fix deadlock with nested trans handles

2014-04-30T15:23:23Z

commit 3bbb24b20a8800158c33eca8564f432dd14d0bf3 upstream. Zach found this deadlock that would happen like this btrfs_end_transaction <- reduce trans->use_count to 0 btrfs_run_delayed_refs btrfs_cow_block find_free_extent btrfs_start_transaction <- increase trans->use_count to 1 allocate chunk btrfs_end_transaction <- decrease trans->use_count to 0 btrfs_run_delayed_refs lock tree block we are cowing above ^^ We need to only decrease trans->use_count if it is above 1, otherwise leave it alone. This will make nested trans be the only ones who decrease their added ref, and will let us get rid of the trans->use_count++ hack if we have to commit the transaction. Thanks, Reported-by: Zach Brown Signed-off-by: Josef Bacik Tested-by: Zach Brown Signed-off-by: Chris Mason [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

Btrfs: fix tree corruption after multi-thread snapshots and inode_cache flush

2011-11-15T14:53:28Z

The btrfs snapshotting code requires that once a root has been snapshotted, we don't change it during a commit. But there are two cases to lead to tree corruptions: 1) multi-thread snapshots can commit serveral snapshots in a transaction, and this may change the src root when processing the following pending snapshots, which lead to the former snapshots corruptions; 2) the free inode cache was changing the roots when it root the cache, which lead to corruptions. This fixes things by making sure we force COW the block after we create a snapshot during commiting a transaction, then any changes to the roots will result in COW, and we get all the fs roots and snapshot roots to be consistent. Signed-off-by: Liu Bo Signed-off-by: Miao Xie Signed-off-by: Chris Mason

Btrfs: fix deadlock caused by the race between relocation

2011-11-11T01:45:05Z

We can not do flushable reservation for the relocation when we create snapshot, because it may make the transaction commit task and the flush task wait for each other and the deadlock happens. Signed-off-by: Miao Xie Signed-off-by: Chris Mason

Btrfs: fix race during transaction joins

2011-11-06T08:26:19Z

While we're allocating ram for a new transaction, we drop our spinlock. When we get the lock back, we do check to see if a transaction started while we slept, but we don't check to make sure it isn't blocked because a commit has already started. Signed-off-by: Chris Mason

Btrfs: ClearPageError during writepage and clean_tree_block

2011-11-06T08:04:20Z

Failure testing was tripping up over stale PageError bits in metadata pages. If we have an io error on a block, and later on end up reusing it, nobody ever clears PageError on those pages. During commit, we'll find PageError and think we had trouble writing the block, which will lead to aborts and other problems. This changes clean_tree_block and the btrfs writepage code to clear the PageError bit. In both cases we're either completely done with the page or the page has good stuff and the error bit is no longer valid. Signed-off-by: Chris Mason

btrfs: separate superblock items out of fs_info

2011-11-06T08:04:01Z

fs_info has now ~9kb, more than fits into one page. This will cause mount failure when memory is too fragmented. Top space consumers are super block structures super_copy and super_for_commit, ~2.8kb each. Allocate them dynamically. fs_info will be ~3.5kb. (measured on x86_64) Add a wrapper for freeing fs_info and all of it's dynamically allocated members. Signed-off-by: David Sterba

Btrfs: seperate out btrfs_block_rsv_check out into 2 different functions

2011-10-19T19:12:59Z

Currently btrfs_block_rsv_check does 2 things, it will either refill a block reserve like in the truncate or refill case, or it will check to see if there is enough space in the global reserve and possibly refill it. However because of overcommit we could be well overcommitting ourselves just to try and refill the global reserve, when really we should just be committing the transaction. So breack this out into btrfs_block_rsv_refill and btrfs_block_rsv_check. Refill will try to reserve more metadata if it can and btrfs_block_rsv_check will not, it will only tell you if the factor of the total space is still reserved. Thanks, Signed-off-by: Josef Bacik

Btrfs: release trans metadata bytes before flushing delayed refs

2011-10-19T19:12:58Z

We started setting trans->block_rsv = NULL to allow the delayed refs flushing stuff to use the right block_rsv and then just made btrfs_trans_release_metadata() unconditionally use the trans block rsv. The problem with this is we need to reserve some space in the transaction and then migrate it to the global block rsv, so we need to be able to free that out properly. So instead just move btrfs_trans_release_metadata() before the delayed ref flushing and use trans->block_rsv for the freeing. Thanks, Signed-off-by: Josef Bacik

Btrfs: introduce mount option no_space_cache

2011-10-19T19:12:51Z

Some users have requested this and I've found I needed a way to disable cache loading without actually clearing the cache, so introduce the no_space_cache option. Before we check the super blocks cache generation field and if it was populated we always turned space caching on. Now we check this and set the space cache option on, and then parse the mount options so that if we want it off it get's turned off. Then we check the mount option all the places we do the caching work instead of checking the super's cache generation. This makes things more consistent and lets us turn space caching off. Thanks, Signed-off-by: Josef Bacik

Btrfs: stop using write_one_page

2011-10-19T19:12:48Z

While looking for a performance regression a user was complaining about, I noticed that we had a regression with the varmail test of filebench. This was introduced by 0d10ee2e6deb5c8409ae65b970846344897d5e4e which keeps us from calling writepages in writepage. This is a correct change, however it happens to help the varmail test because we write out in larger chunks. This is largly to do with how we write out dirty pages for each transaction. If you run filebench with load varmail set $dir=/mnt/btrfs-test run 60 prior to this patch you would get ~1420 ops/second, but with the patch you get ~1200 ops/second. This is a 16% decrease. So since we know the range of dirty pages we want to write out, don't write out in one page chunks, write out in ranges. So to do this we call filemap_fdatawrite_range() on the range of bytes. Then we convert the DIRTY extents to NEED_WAIT extents. When we then call btrfs_wait_marked_extents() we only have to filemap_fdatawait_range() on that range and clear the NEED_WAIT extents. This doesn't get us back to our original speeds, but I've been seeing ~1380 ops/second, which is a <5% regression as opposed to a >15% regression. That is acceptable given that the original commit greatly reduces our latency to begin with. Thanks, Signed-off-by: Josef Bacik