path: root/fs/btrfs/relocation.c
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2009-12-17Btrfs: Add delayed iputYan, Zheng-2/+2
iput() can trigger new transactions if we are dropping the final reference, so calling it in btrfs_commit_transaction may end up deadlock. This patch adds delayed iput to avoid the issue. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-12-17Btrfs: Make truncate(2) more ENOSPC friendlyYan, Zheng-13/+20
truncating and deleting regular files are unbound operations, so it's not good to do them in a single transaction. This patch makes btrfs_truncate and btrfs_delete_inode start a new transaction after all items in a tree leaf are deleted. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-12-17Btrfs: Avoid orphan inodes cleanup while replaying logYan, Zheng-0/+1
We do log replay in a single transaction, so it's not good to do unbound operations. This patch cleans up orphan inodes cleanup after replaying the log. It also avoids doing other unbound operations such as truncating a file during replaying log. These unbound operations are postponed to the orphan inode cleanup stage. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-10-05Btrfs: fix deadlock on async thread startupChris Mason-2/+2
The btrfs async worker threads are used for a wide variety of things, including processing bio end_io functions. This means that when the endio threads aren't running, the rest of the FS isn't able to do the final processing required to clear PageWriteback. The endio threads also try to exit as they become idle and start more as the work piles up. The problem is that starting more threads means kthreadd may need to allocate ram, and that allocation may wait until the global number of writeback pages on the system is below a certain limit. The result of that throttling is that end IO threads wait on kthreadd, who is waiting on IO to end, which will never happen. This commit fixes the deadlock by handing off thread startup to a dedicated thread. It also fixes a bug where the on-demand thread creation was creating far too many threads because it didn't take into account threads being started by other procs. Signed-off-by: Chris Mason <>
2009-09-24Btrfs: relocate file extents in clustersYan, Zheng-89/+148
The extent relocation code copy file extents one by one when relocating data block group. This is inefficient if file extents are small. This patch makes the relocation code copy file extents in clusters. So we can can make better use of read-ahead. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-09-21Btrfs: add snapshot/subvolume destroy ioctlYan, Zheng-6/+35
This patch adds snapshot/subvolume destroy ioctl. A subvolume that isn't being used and doesn't contains links to other subvolumes can be destroyed. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-09-11Btrfs: use a cached state for extent state operations during delallocChris Mason-1/+1
This changes the btrfs code to find delalloc ranges in the extent state tree to use the new state caching code from set/test bit. It reduces one of the biggest causes of rbtree searches in the writeback path. test_range_bit is also modified to take the cached state as a starting point while searching. Signed-off-by: Chris Mason <>
2009-09-11Btrfs: switch extent_map to a rw lockChris Mason-2/+2
There are two main users of the extent_map tree. The first is regular file inodes, where it is evenly spread between readers and writers. The second is the chunk allocation tree, which maps blocks from logical addresses to phyiscal ones, and it is 99.99% reads. The mapping tree is a point of lock contention during heavy IO workloads, so this commit switches things to a rw lock. Signed-off-by: Chris Mason <>
2009-08-07Btrfs: fix balancing oops when invalidate_inode_pages2 returns EBUSYYan Zheng-2/+7
invalidate_inode_pages2_range may return -EBUSY occasionally which results Oops. This patch fixes the issue by moving invalidate_inode_pages2_range into a loop and keeping calling it until the return value is not -EBUSY. The EBUSY return is temporary, and can happen when the btrfs release page function is unable to release a page because the EXTENT_LOCK bit is set. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-07-22Btrfs: fix locking issue in btrfs_find_next_keyYan Zheng-0/+3
When walking up the tree, btrfs_find_next_key assumes the upper level tree block is properly locked. This isn't always true even path->keep_locks is 1. This is because btrfs_find_next_key may advance path->slots[] several times instead of only once. When 'path->slots[level] >= btrfs_header_nritems(path->nodes[level])' is found, we can't guarantee the original value of 'path->slots[level]' is 'btrfs_header_nritems(path->nodes[level]) - 1'. If it's not, the tree block at 'level + 1' isn't locked. This patch fixes the issue by explicitly checking the locking state, re-searching the tree if it's not locked. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-07-02Btrfs: update backrefs while dropping snapshotYan Zheng-4/+1
The new backref format has restriction on type of backref item. If a tree block isn't referenced by its owner tree, full backrefs must be used for the pointers in it. When a tree block loses its owner tree's reference, backrefs for the pointers in it should be updated to full backrefs. Current btrfs_drop_snapshot misses the code that updates backrefs, so it's unsafe for general use. This patch adds backrefs update code to btrfs_drop_snapshot. It isn't a problem in the restricted form btrfs_drop_snapshot is used today, but for general snapshot deletion this update is required. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>
2009-06-10Btrfs: Mixed back reference (FORWARD ROLLING FORMAT CHANGE)Yan Zheng-0/+3711
This commit introduces a new kind of back reference for btrfs metadata. Once a filesystem has been mounted with this commit, IT WILL NO LONGER BE MOUNTABLE BY OLDER KERNELS. When a tree block in subvolume tree is cow'd, the reference counts of all extents it points to are increased by one. At transaction commit time, the old root of the subvolume is recorded in a "dead root" data structure, and the btree it points to is later walked, dropping reference counts and freeing any blocks where the reference count goes to 0. The increments done during cow and decrements done after commit cancel out, and the walk is a very expensive way to go about freeing the blocks that are no longer referenced by the new btree root. This commit reduces the transaction overhead by avoiding the need for dead root records. When a non-shared tree block is cow'd, we free the old block at once, and the new block inherits old block's references. When a tree block with reference count > 1 is cow'd, we increase the reference counts of all extents the new block points to by one, and decrease the old block's reference count by one. This dead tree avoidance code removes the need to modify the reference counts of lower level extents when a non-shared tree block is cow'd. But we still need to update back ref for all pointers in the block. This is because the location of the block is recorded in the back ref item. We can solve this by introducing a new type of back ref. The new back ref provides information about pointer's key, level and in which tree the pointer lives. This information allow us to find the pointer by searching the tree. The shortcoming of the new back ref is that it only works for pointers in tree blocks referenced by their owner trees. This is mostly a problem for snapshots, where resolving one of these fuzzy back references would be O(number_of_snapshots) and quite slow. The solution used here is to use the fuzzy back references in the common case where a given tree block is only referenced by one root, and use the full back references when multiple roots have a reference on a given block. This commit adds per subvolume red-black tree to keep trace of cached inodes. The red-black tree helps the balancing code to find cached inodes whose inode numbers within a given range. This commit improves the balancing code by introducing several data structures to keep the state of balancing. The most important one is the back ref cache. It caches how the upper level tree blocks are referenced. This greatly reduce the overhead of checking back ref. The improved balancing code scales significantly better with a large number of snapshots. This is a very large commit and was written in a number of pieces. But, they depend heavily on the disk format change and were squashed together to make sure git bisect didn't end up in a bad state wrt space balancing or the format change. Signed-off-by: Yan Zheng <> Signed-off-by: Chris Mason <>