Commit Graph

44 Commits

Author SHA1 Message Date
Yan Zheng
5d4f98a28c Btrfs: Mixed back reference (FORWARD ROLLING FORMAT CHANGE)
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 <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-06-10 11:29:46 -04:00
Chris Mason
d397712bcc Btrfs: Fix checkpatch.pl warnings
There were many, most are fixed now.  struct-funcs.c generates some warnings
but these are bogus.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-01-05 21:25:51 -05:00
Chris Mason
c8b978188c Btrfs: Add zlib compression support
This is a large change for adding compression on reading and writing,
both for inline and regular extents.  It does some fairly large
surgery to the writeback paths.

Compression is off by default and enabled by mount -o compress.  Even
when the -o compress mount option is not used, it is possible to read
compressed extents off the disk.

If compression for a given set of pages fails to make them smaller, the
file is flagged to avoid future compression attempts later.

* While finding delalloc extents, the pages are locked before being sent down
to the delalloc handler.  This allows the delalloc handler to do complex things
such as cleaning the pages, marking them writeback and starting IO on their
behalf.

* Inline extents are inserted at delalloc time now.  This allows us to compress
the data before inserting the inline extent, and it allows us to insert
an inline extent that spans multiple pages.

* All of the in-memory extent representations (extent_map.c, ordered-data.c etc)
are changed to record both an in-memory size and an on disk size, as well
as a flag for compression.

From a disk format point of view, the extent pointers in the file are changed
to record the on disk size of a given extent and some encoding flags.
Space in the disk format is allocated for compression encoding, as well
as encryption and a generic 'other' field.  Neither the encryption or the
'other' field are currently used.

In order to limit the amount of data read for a single random read in the
file, the size of a compressed extent is limited to 128k.  This is a
software only limit, the disk format supports u64 sized compressed extents.

In order to limit the ram consumed while processing extents, the uncompressed
size of a compressed extent is limited to 256k.  This is a software only limit
and will be subject to tuning later.

Checksumming is still done on compressed extents, and it is done on the
uncompressed version of the data.  This way additional encodings can be
layered on without having to figure out which encoding to checksum.

Compression happens at delalloc time, which is basically singled threaded because
it is usually done by a single pdflush thread.  This makes it tricky to
spread the compression load across all the cpus on the box.  We'll have to
look at parallel pdflush walks of dirty inodes at a later time.

Decompression is hooked into readpages and it does spread across CPUs nicely.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-10-29 14:49:59 -04:00
Yan Zheng
3bb1a1bc42 Btrfs: Remove offset field from struct btrfs_extent_ref
The offset field in struct btrfs_extent_ref records the position
inside file that file extent is referenced by. In the new back
reference system, tree leaves holding references to file extent
are recorded explicitly. We can scan these tree leaves very quickly, so the
offset field is not required.

This patch also makes the back reference system check the objectid
when extents are in deleting.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
2008-10-09 11:46:24 -04:00
Zheng Yan
31840ae1a6 Btrfs: Full back reference support
This patch makes the back reference system to explicit record the
location of parent node for all types of extents. The location of
parent node is placed into the offset field of backref key. Every
time a tree block is balanced, the back references for the affected
lower level extents are updated.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:07 -04:00
Yan
bcc63abbf3 Btrfs: implement memory reclaim for leaf reference cache
The memory reclaiming issue happens when snapshot exists. In that
case, some cache entries may not be used during old snapshot dropping,
so they will remain in the cache until umount.

The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
the patch makes all dead roots of a given snapshot linked together in order of
create time. After a old snapshot was completely dropped, we check the dead
root list and remove all cache entries created before the oldest dead root in
the list.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:05 -04:00
Chris Mason
ca7a79ad8d Btrfs: Pass down the expected generation number when reading tree blocks
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:03 -04:00
Chris Mason
e17cade25f Btrfs: Add chunk uuids and update multi-device back references
Block headers now store the chunk tree uuid

Chunk items records the device uuid for each stripes

Device extent items record better back refs to the chunk tree

Block groups record better back refs to the chunk tree

The chunk tree format has also changed.  The objectid of BTRFS_CHUNK_ITEM_KEY
used to be the logical offset of the chunk.  Now it is a chunk tree id,
with the logical offset being stored in the offset field of the key.

This allows a single chunk tree to record multiple logical address spaces,
upping the number of bytes indexed by a chunk tree from 2^64 to
2^128.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:01 -04:00
Chris Mason
0d81ba5dbe Btrfs: Move device information into the super block so it can be scanned
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:01 -04:00
Chris Mason
0b86a832a1 Btrfs: Add support for multiple devices per filesystem
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:04:00 -04:00
Chris Mason
7bb86316c3 Btrfs: Add back pointers from extents to the btree or file referencing them
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:03:58 -04:00
Josef Bacik
5103e947b9 xattr support for btrfs
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:03:57 -04:00
Chris Mason
db94535db7 Btrfs: Allow tree blocks larger than the page size
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:03:56 -04:00
Chris Mason
5f39d397df Btrfs: Create extent_buffer interface for large blocksizes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-09-25 11:03:56 -04:00
Zach Brown
ec6b910fb3 Btrfs: trivial include fixups
Almost none of the files including module.h need to do so,
remove them.

Include sched.h in extent-tree.c to silence a warning about cond_resched()
being undeclared.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-07-11 10:00:37 -04:00
Chris Mason
8c2383c3dd Subject: Rework btrfs_file_write to only allocate while page locks are held
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-06-18 09:57:58 -04:00
Chris Mason
6cbd557078 Btrfs: add GPLv2
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-06-12 09:07:21 -04:00
Chris Mason
5af3981c18 Btrfs: printk fixes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-06-12 07:50:13 -04:00
Chris Mason
35b7e47610 Btrfs: fix page cache memory leak
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-05-02 15:53:43 -04:00
Chris Mason
9078a3e1e4 Btrfs: start of block group code
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-04-26 16:46:15 -04:00
Chris Mason
a429e51371 Btrfs: working file_write, reorganized key flags
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-04-18 16:15:28 -04:00
Chris Mason
d0dbc6245c Btrfs: drop owner and parentid
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-04-10 12:36:36 -04:00
Chris Mason
1b05da2ee6 Btrfs: drop the inode map tree
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-04-10 12:13:09 -04:00
Chris Mason
d6e4a428eb Btrfs: start of support for many FS volumes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-04-06 15:37:36 -04:00
Chris Mason
e20d96d64f Mountable btrfs, with readdir
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-22 12:13:20 -04:00
Chris Mason
2e635a2783 Btrfs: initial move to kernel module land
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-21 11:12:56 -04:00
Chris Mason
293ffd5fd3 Btrfs: change dir-test to insert inode_items
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-20 15:57:25 -04:00
Chris Mason
9f5fae2fe6 Btrfs: Add inode map, and the start of file extent items
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-20 14:38:32 -04:00
Chris Mason
a8a2ee0c60 Btrfs: add a name_len to dir items, reorder key
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-16 08:46:49 -04:00
Chris Mason
1d4f6404de Btrfs: directory testing code and dir item fixes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-15 15:18:43 -04:00
Chris Mason
62e2749e03 Btrfs: Use a chunk of the key flags to record the item type.
Add (untested and simple) directory item code
Fix comp_keys to use the new key ordering
Add btrfs_insert_empty_item

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-15 12:56:47 -04:00
Chris Mason
a1516c8921 Btrfs: reorder key offset and flags
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-14 14:26:53 -04:00
Chris Mason
123abc88c9 Btrfs: variable block size support
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-14 14:14:43 -04:00
Chris Mason
4beb1b8b75 Btrfs: add leaf data casting helper
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-14 10:31:29 -04:00
Chris Mason
3768f3689f Btrfs: Change the super to point to a tree of trees to enable persistent snapshots
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-13 16:47:54 -04:00
Chris Mason
234b63a091 rename funcs and structs to btrfs
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-13 10:46:10 -04:00
Chris Mason
1d4f8a0c1e Btrfs: node->blockptrs endian fixes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-13 09:28:32 -04:00
Chris Mason
0783fcfc4d Btrfs: struct item endian fixes
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-12 20:12:07 -04:00
Chris Mason
7518a238ea Btrfs: get/set for struct header fields
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-12 12:01:18 -04:00
Chris Mason
a28ec19775 Btrfs: Fixup reference counting on cows
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-03-06 20:08:01 -05:00
Chris Mason
d16302ab0e Btrfs: more 32 bit cleanups
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-02-26 14:26:58 -05:00
Chris Mason
41903fe666 Btrfs: 32bit cleanups
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-02-26 10:55:42 -05:00
Chris Mason
7cf75962ac Btrfs: u64 cleanups
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-02-26 10:55:01 -05:00
Chris Mason
5de08d7d50 Btrfs: Break up ctree.c a little
Extent fixes

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-02-24 06:24:44 -05:00