A few years ago the btrfs code to support blocks lager than
the page size was disabled to fix a few corner cases in the
page cache handling. This fixes the code to properly support
large metadata blocks again.
Since current kernels will crash early and often with larger
metadata blocks, this adds an incompat bit so that older kernels
can't mount it.
This also does away with different blocksizes for nodes and leaves.
You get a single block size for all tree blocks.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
We encountered an issue that was easily observable on s/390 systems but
could really happen anywhere. The timing just seemed to hit reliably
on s/390 with limited memory.
The gist is that when an unexpected set_page_dirty() happened, we'd
run into the BUG() in btrfs_writepage_fixup_worker since it wasn't
properly set up for delalloc.
This patch does the following:
- Performs the missing delalloc in the fixup worker
- Allow the start hook to return -EBUSY which informs __extent_writepage
that it should mark the page skipped and not to redirty it. This is
required since the fixup worker can fail with -ENOSPC and the page
will have already been redirtied. That causes an Oops in
drop_outstanding_extents later. Retrying the fixup worker could
lead to an infinite loop. Deferring the page redirty also saves us
some cycles since the page would be stuck in a resubmit-redirty loop
until the fixup worker completes. It's not harmful, just wasteful.
- If the fixup worker fails, we mark the page and mapping as errored,
and end the writeback, similar to what we would do had the page
actually been submitted to writeback.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
This patch adds the possibilty to read-lock an extent even if it is already
write-locked from the same thread. btrfs_find_all_roots() needs this
capability.
Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
My previous patch introduced some u64 for failed_mirror variables, this one
makes it consistent again.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
write_cache_pages tries to build up a large bio to stuff down the pipe.
But if it needs to wait for a page lock, it needs to make sure and send
down any pending writes so we don't deadlock with anyone who has the
page lock and is waiting for writeback of things inside the bio.
Dave Sterba triggered this as a deadlock between the autodefrag code and
the extent write_cache_pages
Signed-off-by: Chris Mason <chris.mason@oracle.com>
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
0d10ee2e6d
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 <josef@redhat.com>
If I have a range where I know a certain bit is and I want to set it to another
bit the only option I have is to call set and then clear bit, which will result
in 2 tree searches. This is inefficient, so introduce convert_extent_bit which
will go through and set the bit I want and clear the old bit I don't want.
Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
Add a READAHEAD extent buffer flag.
Add a function to trigger a read with this flag set.
Changes v2:
- use extent buffer flags instead of extent state flags
Changes v5:
- adapt to changed read_extent_buffer_pages interface
- don't return eb from reada_tree_block_flagged if it has CORRUPT flag set
Signed-off-by: Arne Jansen <sensille@gmx.net>
read_extent_buffer_pages currently has two modes, either trigger a read
without waiting for anything, or wait for the I/O to finish. The former
also bails when it's unable to lock the page. This patch now adds an
additional parameter to allow it to block on page lock, but don't wait
for completion.
Changes v5:
- merge the 2 wait parameters into one and define WAIT_NONE, WAIT_COMPLETE and
WAIT_PAGE_LOCK
Change v6:
- fix bug introduced in v5
Signed-off-by: Arne Jansen <sensille@gmx.net>
The raid-retry code in inode.c can be generalized so that it works for
metadata as well. Thus, this patch moves it to extent_io.c and makes the
raid-retry code a raid-repair code.
Repair works that way: Whenever a read error occurs and we have more
mirrors to try, note the failed mirror, and retry another. If we find a
good one, check if we did note a failure earlier and if so, do not allow
the read to complete until after the bad sector was written with the good
data we just fetched. As we have the extent locked while reading, no one
can change the data in between.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
This removes a FIXME comment and introduces the first part of nodatasum
fixup: It gets the corresponding inode for a logical address and triggers a
regular readpage for the corrupted sector.
Once we have on-the-fly error correction our error will be automatically
corrected. The correction code is expected to clear the newly introduced
EXTENT_DAMAGED flag, making scrub report that error as "corrected" instead
of "uncorrectable" eventually.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Currently, extent_read_full_page always assumes we are trying to read mirror
0, which generally is the best we can do. To add flexibility, pass it as a
parameter. This will be needed by scrub fixup code.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
These members are not used at all.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The set/clear bit and the extent split/merge hooks only ever return 0.
Changing them to return void simplifies the error handling cases later.
This patch changes the hook prototypes, the single implementation of each,
and the functions that call them to return void instead.
Since all four of these hooks execute under a spinlock, they're necessarily
simple.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The btrfs metadata btree is the source of significant
lock contention, especially in the root node. This
commit changes our locking to use a reader/writer
lock.
The lock is built on top of rw spinlocks, and it
extends the lock tracking to remember if we have a
read lock or a write lock when we go to blocking. Atomics
count the number of blocking readers or writers at any
given time.
It removes all of the adaptive spinning from the old code
and uses only the spinning/blocking hints inside of btrfs
to decide when it should continue spinning.
In read heavy workloads this is dramatically faster. In write
heavy workloads we're still faster because of less contention
on the root node lock.
We suffer slightly in dbench because we schedule more often
during write locks, but all other benchmarks so far are improved.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The extent_buffers have a very complex interface where
we use HIGHMEM for metadata and try to cache a kmap mapping
to access the memory.
The next commit adds reader/writer locks, and concurrent use
of this kmap cache would make it even more complex.
This commit drops the ability to use HIGHMEM with extent buffers,
and rips out all of the related code.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Reorder extent_buffer to remove 8 bytes of alignment padding on 64 bit
builds. This shrinks its size to 128 bytes allowing it to fit into one
fewer cache lines and allows more objects per slab in its kmem_cache.
slabinfo extent_buffer reports :-
before:-
Sizes (bytes) Slabs
----------------------------------
Object : 136 Total : 123
SlabObj: 136 Full : 121
SlabSiz: 4096 Partial: 0
Loss : 0 CpuSlab: 2
Align : 8 Objects: 30
after :-
Object : 128 Total : 4
SlabObj: 128 Full : 2
SlabSiz: 4096 Partial: 0
Loss : 0 CpuSlab: 2
Align : 8 Objects: 32
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Remove static and global declarations and/or definitions. Reduces size
of btrfs.ko by ~3.4kB.
text data bss dec hex filename
402081 7464 200 409745 64091 btrfs.ko.base
398620 7144 200 405964 631cc btrfs.ko.remove-all
Signed-off-by: David Sterba <dsterba@suse.cz>
all callers pass GFP_NOFS, but the GFP mask argument is not used in the
function; GFP_ATOMIC is passed to radix tree initialization and it's the
only correct one, since we're using the preload/insert mechanism of
radix tree.
Let's drop the gfp mask from btrfs function, this will not change
behaviour.
Signed-off-by: David Sterba <dsterba@suse.cz>
In several places the sequence (set_extent_uptodate, unlock_extent) is used.
This leads to a duplicate lookup of the extent state. This patch lets
set_extent_uptodate return a cached extent_state which can be passed to
unlock_extent_cached.
The occurences of the above sequences are updated to use the cache. Only
end_bio_extent_readpage is updated that it first gets a cached state to
pass it to the readpage_end_io_hook as the prototype requested and is later
on being used for set/unlock.
Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Currently if we have corrupted items things will blow up in spectacular ways.
So as we read in blocks and they are leaves, check the entire leaf to make sure
all of the items are correct and point to valid parts in the leaf for the item
data the are responsible for. If the item is corrupt we will kick back EIO and
not read any of the copies since they are likely to not be correct either. This
will catch generic corruptions, it will be up to the individual callers of
btrfs_search_slot to make sure their items are right. Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
The Btrfs fiemap code wasn't properly returning delalloc extents,
so applications that trust fiemap to decide if there are holes in the
file see holes instead of delalloc.
This reworks the btrfs fiemap code, adding a get_extent helper that
searches for delalloc ranges and also adding a helper for extent_fiemap
that skips past holes in the file.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Make the code aware of compression type, instead of always assuming
zlib compression.
Also make the zlib workspace function as common code for all
compression types.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
extent_bio_alloc() and compressed_bio_alloc() are similar, cleanup
similar source code.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch reduces the CPU time spent in the extent buffer search by using the
radix tree instead of the rbtree and using the rcu lock instead of the spin
lock.
I did a quick test by the benchmark tool[1] and found the patch improve the
file creation/deletion performance problem that I have reported[2].
Before applying this patch:
Create files:
Total files: 50000
Total time: 0.971531
Average time: 0.000019
Delete files:
Total files: 50000
Total time: 1.366761
Average time: 0.000027
After applying this patch:
Create files:
Total files: 50000
Total time: 0.927455
Average time: 0.000019
Delete files:
Total files: 50000
Total time: 1.292280
Average time: 0.000026
[1] http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3
[2] http://marc.info/?l=linux-btrfs&m=128212635122920&w=2
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This changes O_DIRECT write code to mark extents as delalloc
while it is processing them. Yan Zheng has reworked the
enospc accounting based on tracking delalloc extents and
this makes it much easier to track enospc in the O_DIRECT code.
There are a few space cases with the O_DIRECT code though,
it only sets the EXTENT_DELALLOC bits, instead of doing
EXTENT_DELALLOC | EXTENT_DIRTY | EXTENT_UPTODATE, because
we don't want to mess with clearing the dirty and uptodate
bits when things go wrong. This is important because there
are no pages in the page cache, so any extent state structs
that we put in the tree won't get freed by releasepage. We have
to clear them ourselves as the DIO ends.
With this commit, we reserve space at in btrfs_file_aio_write,
and then as each btrfs_direct_IO call progresses it sets
EXTENT_DELALLOC on the range.
btrfs_get_blocks_direct is responsible for clearing the delalloc
at the same time it drops the extent lock.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The async helper threads offload crc work onto all the
CPUs, and make streaming writes much faster. This
changes the O_DIRECT write code to use them. The only
small complication was that we need to pass in the
logical offset in the file for each bio, because we can't
find it in the bio's pages.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Introduce metadata reservation context for delayed allocation
and update various related functions.
This patch also introduces EXTENT_FIRST_DELALLOC control bit for
set/clear_extent_bit. It tells set/clear_bit_hook whether they
are processing the first extent_state with EXTENT_DELALLOC bit
set. This change is important if set/clear_extent_bit involves
multiple extent_state.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch just goes through and fixes everybody that does
lock_extent()
blah
unlock_extent()
to use
lock_extent_bits()
blah
unlock_extent_cached()
and pass around a extent_state so we only have to do the searches once per
function. This gives me about a 3 mb/s boots on my random write test. I have
not converted some things, like the relocation and ioctl's, since they aren't
heavily used and the relocation stuff is in the middle of being re-written. I
also changed the clear_extent_bit() to only unset the cached state if we are
clearing EXTENT_LOCKED and related stuff, so we can do things like this
lock_extent_bits()
clear delalloc bits
unlock_extent_cached()
without losing our cached state. I tested this thoroughly and turned on
LEAK_DEBUG to make sure we weren't leaking extent states, everything worked out
fine.
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch fixes an issue with the delalloc metadata space reservation
code. The problem is we used to free the reservation as soon as we
allocated the delalloc region. The problem with this is if we are not
inserting an inline extent, we don't actually insert the extent item until
after the ordered extent is written out. This patch does 3 things,
1) It moves the reservation clearing stuff into the ordered code, so when
we remove the ordered extent we remove the reservation.
2) It adds a EXTENT_DO_ACCOUNTING flag that gets passed when we clear
delalloc bits in the cases where we want to clear the metadata reservation
when we clear the delalloc extent, in the case that we do an inline extent
or we invalidate the page.
3) It adds another waitqueue to the space info so that when we start a fs
wide delalloc flush, anybody else who also hits that area will simply wait
for the flush to finish and then try to make their allocation.
This has been tested thoroughly to make sure we did not regress on
performance.
Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
extent_clear_unlock_delalloc has a growing set of ugly parameters
that is very difficult to read and maintain.
This switches to a flag field and well named flag defines.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
At the start of a transaction we do a btrfs_reserve_metadata_space() and
specify how many items we plan on modifying. Then once we've done our
modifications and such, just call btrfs_unreserve_metadata_space() for
the same number of items we reserved.
For keeping track of metadata needed for data I've had to add an extent_io op
for when we merge extents. This lets us track space properly when we are doing
sequential writes, so we don't end up reserving way more metadata space than
what we need.
The only place where the metadata space accounting is not done is in the
relocation code. This is because Yan is going to be reworking that code in the
near future, so running btrfs-vol -b could still possibly result in a ENOSPC
related panic. This patch also turns off the metadata_ratio stuff in order to
allow users to more efficiently use their disk space.
This patch makes it so we track how much metadata we need for an inode's
delayed allocation extents by tracking how many extents are currently
waiting for allocation. It introduces two new callbacks for the
extent_io tree's, merge_extent_hook and split_extent_hook. These help
us keep track of when we merge delalloc extents together and split them
up. Reservations are handled prior to any actually dirty'ing occurs,
and then we unreserve after we dirty.
btrfs_unreserve_metadata_for_delalloc() will make the appropriate
unreservations as needed based on the number of reservations we
currently have and the number of extents we currently have. Doing the
reservation outside of doing any of the actual dirty'ing lets us do
things like filemap_flush() the inode to try and force delalloc to
happen, or as a last resort actually start allocation on all delalloc
inodes in the fs. This has survived dbench, fs_mark and an fsx torture
test.
Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Btrfs writes go through delalloc to the data=ordered code. This
makes sure that all of the data is on disk before the metadata
that references it. The tracking means that we have to make sure
each page in an extent is fully written before we add that extent into
the on-disk btree.
This was done in the past by setting the EXTENT_ORDERED bit for the
range of an extent when it was added to the data=ordered code, and then
clearing the EXTENT_ORDERED bit in the extent state tree as each page
finished IO.
One of the reasons we had to do this was because sometimes pages are
magically dirtied without page_mkwrite being called. The EXTENT_ORDERED
bit is checked at writepage time, and if it isn't there, our page become
dirty without going through the proper path.
These bit operations make for a number of rbtree searches for each page,
and can cause considerable lock contention.
This commit switches from the EXTENT_ORDERED bit to use PagePrivate2.
As pages go into the ordered code, PagePrivate2 is set on each one.
This is a cheap operation because we already have all the pages locked
and ready to go.
As IO finishes, the PagePrivate2 bit is cleared and the ordered
accoutning is updated for each page.
At writepage time, if the PagePrivate2 bit is missing, we go into the
writepage fixup code to handle improperly dirtied pages.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
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 <chris.mason@oracle.com>
Many of the btrfs extent state tree users follow the same pattern.
They lock an extent range in the tree, do some operation and then
unlock.
This translates to at least 2 rbtree searches, and maybe more if they
are doing operations on the extent state tree. A locked extent
in the tree isn't going to be merged or changed, and so we can
safely return the extent state structure as a cached handle.
This changes set_extent_bit to give back a cached handle, and also
changes both set_extent_bit and clear_extent_bit to use the cached
handle if it is available.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Btrfs is currently mirroring some of the page state bits into
its extent state tree. The goal behind this was to use it in supporting
blocksizes other than the page size.
But, we don't currently support that, and we're using quite a lot of CPU
on the rb tree and its spin lock. This commit starts a series of
cleanups to reduce the amount of work done in the extent state tree as
part of each IO.
This commit:
* Adds the ability to lock an extent in the state tree and also set
other bits. The idea is to do locking and delalloc in one call
* Removes the EXTENT_WRITEBACK and EXTENT_DIRTY bits. Btrfs is using
a combination of the page bits and the ordered write code for this
instead.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
btrfs_mark_buffer dirty would set dirty bits in the extent_io tree
for the buffers it was dirtying. This may require a kmalloc and it
was not atomic. So, anyone who called btrfs_mark_buffer_dirty had to
set any btree locks they were holding to blocking first.
This commit changes dirty tracking for extent buffers to just use a flag
in the extent buffer. Now that we have one and only one extent buffer
per page, this can be safely done without losing dirty bits along the way.
This also introduces a path->leave_spinning flag that callers of
btrfs_search_slot can use to indicate they will properly deal with a
path returned where all the locks are spinning instead of blocking.
Many of the btree search callers now expect spinning paths,
resulting in better btree concurrency overall.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Most of the btrfs metadata operations can be protected by a spinlock,
but some operations still need to schedule.
So far, btrfs has been using a mutex along with a trylock loop,
most of the time it is able to avoid going for the full mutex, so
the trylock loop is a big performance gain.
This commit is step one for getting rid of the blocking locks entirely.
btrfs_tree_lock takes a spinlock, and the code explicitly switches
to a blocking lock when it starts an operation that can schedule.
We'll be able get rid of the blocking locks in smaller pieces over time.
Tracing allows us to find the most common cause of blocking, so we
can start with the hot spots first.
The basic idea is:
btrfs_tree_lock() returns with the spin lock held
btrfs_set_lock_blocking() sets the EXTENT_BUFFER_BLOCKING bit in
the extent buffer flags, and then drops the spin lock. The buffer is
still considered locked by all of the btrfs code.
If btrfs_tree_lock gets the spinlock but finds the blocking bit set, it drops
the spin lock and waits on a wait queue for the blocking bit to go away.
Much of the code that needs to set the blocking bit finishes without actually
blocking a good percentage of the time. So, an adaptive spin is still
used against the blocking bit to avoid very high context switch rates.
btrfs_clear_lock_blocking() clears the blocking bit and returns
with the spinlock held again.
btrfs_tree_unlock() can be called on either blocking or spinning locks,
it does the right thing based on the blocking bit.
ctree.c has a helper function to set/clear all the locked buffers in a
path as blocking.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Now that bmap support is gone, this is the only way to get extent
mappings for userland. These are still not valid for IO, but they
can tell us if a file has holes or how much fragmentation there is.
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Checksums on data can be disabled by mount option, so it's
possible some data extents don't have checksums or have
invalid checksums. This causes trouble for data relocation.
This patch contains following things to make data relocation
work.
1) make nodatasum/nodatacow mount option only affects new
files. Checksums and COW on data are only controlled by the
inode flags.
2) check the existence of checksum in the nodatacow checker.
If checksums exist, force COW the data extent. This ensure that
checksum for a given block is either valid or does not exist.
3) update data relocation code to properly handle the case
of checksum missing.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
When reading compressed extents, try to put pages into the page cache
for any pages covered by the compressed extent that readpages didn't already
preload.
Add an async work queue to handle transformations at delayed allocation processing
time. Right now this is just compression. The workflow is:
1) Find offsets in the file marked for delayed allocation
2) Lock the pages
3) Lock the state bits
4) Call the async delalloc code
The async delalloc code clears the state lock bits and delalloc bits. It is
important this happens before the range goes into the work queue because
otherwise it might deadlock with other work queue items that try to lock
those extent bits.
The file pages are compressed, and if the compression doesn't work the
pages are written back directly.
An ordered work queue is used to make sure the inodes are written in the same
order that pdflush or writepages sent them down.
This changes extent_write_cache_pages to let the writepage function
update the wbc nr_written count.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch removes the giant fs_info->alloc_mutex and replaces it with a bunch
of little locks.
There is now a pinned_mutex, which is used when messing with the pinned_extents
extent io tree, and the extent_ins_mutex which is used with the pending_del and
extent_ins extent io trees.
The locking for the extent tree stuff was inspired by a patch that Yan Zheng
wrote to fix a race condition, I cleaned it up some and changed the locking
around a little bit, but the idea remains the same. Basically instead of
holding the extent_ins_mutex throughout the processing of an extent on the
extent_ins or pending_del trees, we just hold it while we're searching and when
we clear the bits on those trees, and lock the extent for the duration of the
operations on the extent.
Also to keep from getting hung up waiting to lock an extent, I've added a
try_lock_extent so if we cannot lock the extent, move on to the next one in the
tree and we'll come back to that one. I have tested this heavily and it does
not appear to break anything. This has to be applied on top of my
find_free_extent redo patch.
I tested this patch on top of Yan's space reblancing code and it worked fine.
The only thing that has changed since the last version is I pulled out all my
debugging stuff, apparently I forgot to run guilt refresh before I sent the
last patch out. Thank you,
Signed-off-by: Josef Bacik <jbacik@redhat.com>
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>
* Add an EXTENT_BOUNDARY state bit to keep the writepage code
from merging data extents that are in the process of being
relocated. This allows us to do accounting for them properly.
* The balancing code relocates data extents indepdent of the underlying
inode. The extent_map code was modified to properly account for
things moving around (invalidating extent_map caches in the inode).
* Don't take the drop_mutex in the create_subvol ioctl. It isn't
required.
* Fix walking of the ordered extent list to avoid races with sys_unlink
* Change the lock ordering rules. Transaction start goes outside
the drop_mutex. This allows btrfs_commit_transaction to directly
drop the relocation trees.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Chris Mason