When btrfs_get_extent is reading inline file items for readpage,
it needs to copy the inline extent into the page.  If the
inline extent doesn't cover all of the page, that means there
is a hole in the file, or that our file is smaller than one
page.

readpage does zeroing for the case where the file is smaller than one
page, but nobody is currently zeroing for the case where there is
a hole after the inline item.

This commit changes btrfs_get_extent to zero fill the page past
the end of the inline item.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

This closes a whole where the page may be written before
the page_mkwrite caller has a chance to dirty it

(thanks to Nick Piggin)
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Data COW means that whenever we write to a file, we replace any old
extent pointers with new ones.  There was a window where a readpage
might find the old extent pointers on disk and cache them in the
extent_map tree in ram in the middle of a given write replacing them.

Even though both the readpage and the write had their respective bytes
in the file locked, the extent readpage inserts may cover more bytes than
it had locked down.

This commit closes the race by keeping the new extent pinned in the extent
map tree until after the on-disk btree is properly setup with the new
extent pointers.
Signed-off-by: NChris 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: NChris 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: NChris Mason <chris.mason@oracle.com>

At writepage time, we have the page locked and we have the
extent_map entry for this extent pinned in the extent_map tree.
So, the page can't go away and its mapping can't change.

There is no need for the extra extent_state lock bits during writepage.
Signed-off-by: NChris 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: NChris 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: NChris Mason <chris.mason@oracle.com>

As the extent state tree is manipulated, there are call backs
that are used to take extra actions when different state bits are set
or cleared.  One example of this is a counter for the total number
of delayed allocation bytes in a single inode and in the whole FS.

When new states are inserted, this callback is being done before we
properly setup the new state.  This hasn't caused problems before
because the lock bit was always done first, and the existing call backs
don't care about the lock bit.

This patch makes sure the state is properly setup before using the
callback, which is important for later optimizations that do more work
without using the lock bit.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

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: NChris Mason <chris.mason@oracle.com>

The btrfs io submission thread tries to back off congested devices in
favor of rotating off to another disk.

But, it tries to make sure it submits at least some IO before rotating
on (the others may be congested too), and so it has a magic number of
requests it tries to write before it hops.

This makes the magic number smaller.  Testing shows that we're spending
too much time on congested devices and leaving the other devices idle.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

When btrfs fills a large delayed allocation extent, it is a good idea
to try and convince the write_cache_pages caller to go ahead and
write a good chunk of that extent.  The extra IO is basically free
because we know it is contiguous.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

This changes the btrfs worker threads to batch work items
into a local list.  It allows us to pull work items in
large chunks and significantly reduces the number of times we
need to take the worker thread spinlock.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The btrfs worker thread spinlock was being used both for the
queueing of IO and for the processing of ordered events.

The ordered events never happen from end_io handlers, and so they
don't need to use the _irq version of spinlocks.  This adds a
dedicated lock to the ordered lists so they don't have to run
with irqs off.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The Btrfs set_extent_bit call currently searches the rbtree
every time it needs to find more extent_state objects to fill
the requested operation.

This adds a simple test with rb_next to see if the next object
in the tree was adjacent to the one we just found.  If so,
we skip the search and just use the next object.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The Btrfs worker threads don't currently die off after they have
been idle for a while, leading to a lot of threads sitting around
doing nothing for each mount.

Also, they are unable to start atomically (from end_io hanlders).

This commit reworks the worker threads so they can be started
from end_io handlers (just setting a flag that asks for a thread
to be added at a later date) and so they can exit if they
have been idle for a long time.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

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: NYan Zheng <zheng.yan@oracle.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

find_zlib_workspace returns an ERR_PTR value in an error case instead of NULL.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@match exists@
expression x, E;
statement S1, S2;
@@

x = find_zlib_workspace(...)
... when != x = E
(
*  if (x == NULL || ...) S1 else S2
|
*  if (x == NULL && ...) S1 else S2
)
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

This takes care of the following entry from Dan's list:

fs/btrfs/inode.c +4788 btrfs_rename(36) warning: variable derefenced before check 'old_inode'
Reported-by: NDan Carpenter <error27@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Eugene Teo <eteo@redhat.com>
Cc: Julia Lawall <julia@diku.dk>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The async caching thread can end up looping forever if a given
search puts it at the last key in a leaf.  It will end up calling
btrfs_next_leaf and then checking if it needs to politely drop
the read semaphore.

Most of the time this looping isn't noticed because it is able to
make progress the next time around.  But, during log replay,
we wait on the async caching thread to finish, and the async thread
is waiting on the commit, and no progress is really made.

The fix used here is to copy the key out of the next leaf,
that way our search lands there properly.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Yan Zheng hit a problem where we tried to remove some free space but failed
because we couldn't find the free space entry.  This is because the free space
was held within a bitmap that had a starting offset well before the actual
offset of the free space, and there were free space extents that were in the
same range as that offset, so tree_search_offset returned with NULL because we
couldn't find a free space extent that had that offset.  This is fixed by
making sure that if we fail to find the entry, we re-search again with
bitmap_only set to 1 and do an offset_to_bitmap so we can get the appropriate
bitmap.  A similar problem happens in btrfs_alloc_from_bitmap for the
clustering code, but that is not as bad since we will just go and redo our
cluster allocation.

Also this adds some debugging checks to make sure that the free space we are
trying to remove from the bitmap is in fact there.  This can probably go away
after a while, but since this code is only used by the tree-logging stuff it
would be nice to run with it for a while to make sure there are no problems.
Signed-off-by: NJosef Bacik <jbacik@redhat.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The semaphore used by the async caching threads can prevent a
transaction commit, which can make the FS appear to stall.  This
releases the semaphore more often when a transaction commit is
in progress.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The async block group caching code uses the commit_root pointer
to get a stable version of the extent allocation tree for scanning.
This copy of the tree root isn't going to change and it significantly
reduces the complexity of the scanning code.

During a commit, we have a loop where we update the extent allocation
tree root.  We need to loop because updating the root pointer in
the tree of tree roots may allocate blocks which may change the
extent allocation tree.

Right now the commit_root pointer is changed inside this loop.  It
is more correct to change the commit_root pointer only after all the
looping is done.
Signed-off-by: NYan Zheng <zheng.yan@oracle.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

- don't stop the caching thread until btrfs_commit_super return.

- if caching is interrupted by umount, set last to (u64)-1.
  otherwise the un-scanned range of block group will be considered
  as free extent.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

We are racy with async block caching and unpinning extents.  This patch makes
things much less complicated by only unpinning the extent if the block group is
cached.  We check the block_group->cached var under the block_group->lock spin
lock.  If it is set to BTRFS_CACHE_FINISHED then we update the pinned counters,
and unpin the extent and add the free space back.  If it is not set to this, we
start the caching of the block group so the next time we unpin extents we can
unpin the extent.  This keeps us from racing with the async caching threads,
lets us kill the fs wide async thread counter, and keeps us from having to set
DELALLOC bits for every extent we hit if there are caching kthreads going.

One thing that needed to be changed was btrfs_free_super_mirror_extents.  Now
instead of just looking for LOCKED extents, we also look for DIRTY extents,
since we could have left some extents pinned in the previous transaction that
will never get freed now that we are unmounting, which would cause us to leak
memory.  So btrfs_free_super_mirror_extents has been changed to
btrfs_free_pinned_extents, and it will clear the extents locked for the super
mirror, and any remaining pinned extents that may be present.  Thank you,
Signed-off-by: NJosef Bacik <jbacik@redhat.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

dir has already been tested.  It seems that this test should be on the
recently returned value inode.

A simplified version of the semantic match that finds this problem is as
follows: (http://www.emn.fr/x-info/coccinelle/)
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Allocating new block group is easy when the disk has plenty of space.
But things get difficult as the disk fills up, especially if
the FS has been run through btrfs-vol -b.  The balance operation
is likely to make the total bytes available on the device greater
than the largest extent we'll actually be able to allocate.

But the device extent allocation code incorrectly assumes that a device
with 5G free will be able to allocate a 5G extent.  It isn't normally a
problem because device extents don't get freed unless btrfs-vol -b
is run.

This fixes the device extent allocator to remember the largest free
extent it can find, and then uses that value as a fallback.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Btrfs allocates individual extents from block groups, and each
block group has a specific type.  It may hold metadata, data
mirrored or striped etc.

When we balance space (btrfs-vol -b) or remove a drive (btrfs-vol -r)
we free block groups.  Once a block group is freed, the space it was
using on the device may be available for use by new block groups.

btrfs_remove_block_group was clearing the flag that said
'our devices are full, don't even try to allocate new block groups',
but it was only clearing that flag for a specific type of block group.

This commit clears the full flag for all of the types of block groups,
making it much more likely that we'll be able to balance space when
the drive is close to full.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The commit_transaction call to wait_ordered_extents when snap_pending
passes nocow_only=1 to process only NOCOW or PREALLOC extents.  This isn't
correct for the 'flushoncommit' mode, as it skips extents we just started
IO on in start_delalloc_inodes.

So, in the flushoncommit case, wait on all ordered extents.  Otherwise,
only pass the nocow_only flag to wait_ordered_extents if snap_pending.
Signed-off-by: NSage Weil <sage@newdream.net>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

btrfs_split_leaf and btrfs_del_items can end up in a loop
where one is constantly spliting a given leaf and the other
is constantly merging it back with the adjacent nodes.

There is a better fix for this, but in the interest of something
small, this patch just changes btrfs_del_items back to balancing less
often.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Check objectid of item before checking the item type, otherwise we may return
zero for a key that is actually too low.
Signed-off-by: NYan Zheng <zheng.yan@oracle.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

find_free_dev_extent does not properly handle the case where
the device is not complete free, and there is a free extent
at the beginning of the device.
Signed-off-by: NYan Zheng <zheng.yan@oracle.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

comp_keys is duplicating what is done in btrfs_comp_cpu_keys, so just
call it.
Signed-off-by: NDiego Calleja <diegocg@gmail.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

This patch moves the caching of the block group off to a kthread in order to
allow people to allocate sooner.  Instead of blocking up behind the caching
mutex, we instead kick of the caching kthread, and then attempt to make an
allocation.  If we cannot, we wait on the block groups caching waitqueue, which
the caching kthread will wake the waiting threads up everytime it finds 2 meg
worth of space, and then again when its finished caching.  This is how I tested
the speedup from this

mkfs the disk
mount the disk
fill the disk up with fs_mark
unmount the disk
mount the disk
time touch /mnt/foo

Without my changes this took 11 seconds on my box, with these changes it now
takes 1 second.

Another change thats been put in place is we lock the super mirror's in the
pinned extent map in order to keep us from adding that stuff as free space when
caching the block group.  This doesn't really change anything else as far as the
pinned extent map is concerned, since for actual pinned extents we use
EXTENT_DIRTY, but it does mean that when we unmount we have to go in and unlock
those extents to keep from leaking memory.

I've also added a check where when we are reading block groups from disk, if the
amount of space used == the size of the block group, we go ahead and mark the
block group as cached.  This drastically reduces the amount of time it takes to
cache the block groups.  Using the same test as above, except doing a dd to a
file and then unmounting, it used to take 33 seconds to umount, now it takes 3
seconds.

This version uses the commit_root in the caching kthread, and then keeps track
of how many async caching threads are running at any given time so if one of the
async threads is still running as we cross transactions we can wait until its
finished before handling the pinned extents.  Thank you,
Signed-off-by: NJosef Bacik <jbacik@redhat.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Currently btrfs has a problem where it can use a ridiculous amount of RAM simply
tracking free space.  As free space gets fragmented, we end up with thousands of
entries on an rb-tree per block group, which usually spans 1 gig of area.  Since
we currently don't ever flush free space cache back to disk this gets to be a
bit unweildly on large fs's with lots of fragmentation.

This patch solves this problem by using PAGE_SIZE bitmaps for parts of the free
space cache.  Initially we calculate a threshold of extent entries we can
handle, which is however many extent entries we can cram into 16k of ram.  The
maximum amount of RAM that should ever be used to track 1 gigabyte of diskspace
will be 32k of RAM, which scales much better than we did before.

Once we pass the extent threshold, we start adding bitmaps and using those
instead for tracking the free space.  This patch also makes it so that any free
space thats less than 4 * sectorsize we go ahead and put into a bitmap.  This is
nice since we try and allocate out of the front of a block group, so if the
front of a block group is heavily fragmented and then has a huge chunk of free
space at the end, we go ahead and add the fragmented areas to bitmaps and use a
normal extent entry to track the big chunk at the back of the block group.

I've also taken the opportunity to revamp how we search for free space.
Previously we indexed free space via an offset indexed rb tree and a bytes
indexed rb tree.  I've dropped the bytes indexed rb tree and use only the offset
indexed rb tree.  This cuts the number of tree operations we were doing
previously down by half, and gives us a little bit of a better allocation
pattern since we will always start from a specific offset and search forward
from there, instead of searching for the size we need and try and get it as
close as possible to the offset we want.

I've given this a healthy amount of testing pre-new format stuff, as well as
post-new format stuff.  I've booted up my fedora box which is installed on btrfs
with this patch and ran with it for a few days without issues.  I've not seen
any performance regressions in any of my tests.

Since the last patch Yan Zheng fixed a problem where we could have overlapping
entries, so updating their offset inline would cause problems.  Thanks,
Signed-off-by: NJosef Bacik <jbacik@redhat.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

If the tree roots hit read errors during mount, btrfs is not properly
erroring out.  We need to check the uptodate bits after
reading in the tree root node.
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

This removes the continues call's of btrfs_header_level. One call of
btrfs_header_level(c) its enough.

Signed-off-by Daniel Cadete <danielncadete10@gmail.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Move the call to BUG_ON to before the dereference of the tested value.
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

It was never actually doing anything anyway (see the loop condition),
and it would be difficult to make it work for RAID[56].

Even if it was actually working, it's checking for the wrong thing
anyway. Instead of checking whether we list a block which _doesn't_ land
at the relevant physical location, it should be checking that we _have_
listed all the logical blocks which refer to the required physical
location on all devices.

This function is only called from remove_sb_from_cache() to ensure that
we reserve the logical blocks which would reside at the same physical
location as the superblock copies. So listing more blocks than we need
is actually OK.

With RAID[56] we're going to throw away an entire stripe for each block
we have to ignore, so we _are_ going to list blocks other than the
ones which actually contain the superblock.
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

If spin_lock_irqsave is called twice in a row with the same second
argument, the interrupt state at the point of the second call overwrites
the value saved by the first call.  Indeed, the second call does not need
to save the interrupt state, so it is changed to a simple spin_lock.
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NChris Mason <chris.mason@oracle.com>