This patch moves the delalloc flushing that occurs when we are under space
pressure off to a async thread pool.  This helps since we only free up
metadata space when we actually insert the extent item, which means it takes
quite a while for space to be free'ed up if we wait on all ordered extents.
However, if space is freed up due to inline extents being inserted, we can
wake people who are waiting up early, and they can finish their work.

Signed-off-by: Josef Bacik <jbacik@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>

When compression is on, the cow_file_range code is farmed off to
worker threads.  This allows us to do significant CPU work in parallel
on SMP machines.

But it is a delicate balance around when we clear flags and how.  In
the past we cleared the delalloc flag immediately, which was safe
because the pages stayed locked.

But this is causing problems with the newest ENOSPC code, and with the
recent extent state cleanups we can now clear the delalloc bit at the
same time the uncompressed code does.

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>

Like the cluster allocating stuff, we can lockup the box with the normal
allocation path.  This happens when we

1) Start to cache a block group that is severely fragmented, but has a decent
amount of free space.
2) Start to commit a transaction
3) Have the commit try and empty out some of the delalloc inodes with extents
that are relatively large.

The inodes will not be able to make the allocations because they will ask for
allocations larger than a contiguous area in the free space cache.  So we will
wait for more progress to be made on the block group, but since we're in a
commit the caching kthread won't make any more progress and it already has
enough free space that wait_block_group_cache_progress will just return.  So,
if we wait and fail to make the allocation the next time around, just loop and
go to the next block group.  This keeps us from getting stuck in a softlockup.
Thanks,

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

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 <chris.mason@oracle.com>

There is a problem where page_mkwrite can be called on a dirtied page that
already has a delalloc range associated with it.  The fix is to clear any
delalloc bits for the range we are dirtying so the space accounting gets
handled properly.  This is the same thing we do in the normal write case, so we
are consistent across the board.  With this patch we no longer leak reserved
space.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

btrfs_file_write was incorrectly calling generic_write_checks without
taking i_mutex.  This lead to problems with racing around i_size when
doing O_APPEND writes.

The fix here is to move i_mutex higher.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

wait_on_page_writeback_range/btrfs_wait_on_page_writeback_range takes
a pagecache offset, not a byte offset into the file.  Shift the arguments
around to wait for the correct range

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

If an ioctl-initiated transaction is open, we can't force a commit during
the free space checks in order to free up pinned extents or else we
deadlock.  Just ENOSPC instead.

A more satisfying solution that reserves space for the entire user
transaction up front is forthcoming...

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Fix leak of vfsmount write reference and open_ioctl_trans reference on
ENOMEM.  Clean up the error paths while we're at it.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

We've already defined CONFIG_BTRFS_POSIX_ACL in Kconfig, but we're
currently not using it and are testing CONFIG_FS_POSIX_ACL instead.
CONFIG_FS_POSIX_ACL states "Never use this symbol for ifdefs".

Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Error handling code following a kzalloc should free the allocated data.

The semantic match that finds the problem is as follows:
(http://www.emn.fr/x-info/coccinelle/

)

// <smpl>
@r exists@
local idexpression x;
statement S;
expression E;
identifier f,f1,l;
position p1,p2;
expression *ptr != NULL;
@@

x@p1 = \(kmalloc\|kzalloc\|kcalloc\)(...);
...
if (x == NULL) S
<... when != x
     when != if (...) { <+...x...+> }
(
x->f1 = E
|
 (x->f1 == NULL || ...)
|
 f(...,x->f1,...)
)
...>
(
 return \(0\|<+...x...+>\|ptr\);
|
 return@p2 ...;
)

@script:python@
p1 << r.p1;
p2 << r.p2;
@@

print "* file: %s kmalloc %s return %s" % (p1[0].file,p1[0].line,p2[0].line)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

We currently set sb->s_flags |= MS_POSIXACL unconditionally, which is
incorrect -- it tells the VFS that it shouldn't set umask because we
will, yet we don't set it ourselves if we aren't using POSIX ACLs, so
the umask ends up ignored.

Signed-off-by: Chris Ball <cjb@laptop.org>
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>

The snapshot deletion  patches dropped this line, but the inode
needs to be hashed.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

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

A recent change enforces only one access point to each subvolume. The first
directory entry (the one added when the subvolume/snapshot was created) is
treated as valid access point, all other subvolume links are linked to dummy
empty directories. The dummy directories are temporary inodes that only in
memory, so we can not rename file into them.

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

For every hardlink in btrfs, there is a corresponding inode back
reference. All inode back references for hardlinks in a given
directory are stored in single b-tree item. The size of b-tree item
is limited by the size of b-tree leaf, so we can only create limited
number of hardlinks to a given file in a directory.

The original code lacks of the check, it oops if the number of
hardlinks goes over the limit. This patch fixes the issue by adding
check to btrfs_link and btrfs_rename.

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

During releasepage, we try to drop any extent_state structs for the
bye offsets of the page we're releaseing.  But the code was incorrectly
telling clear_extent_bit to delete the state struct unconditionallly.

Normally this would be fine because we have the page locked, but other
parts of btrfs will lock down an entire extent, the most common place
being IO completion.

releasepage was deleting the extent state without first locking the extent,
which may result in removing a state struct that another process had
locked down.  The fix here is to leave the NODATASUM and EXTENT_LOCKED
bits alone in releasepage.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

If test_range_bit finds an extent that goes all the way to (u64)-1, it
can incorrectly wrap the u64 instead of treaing it like the end of
the address space.

This just adds a check for the highest possible offset so we don't wrap.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

Both set and clear_extent_bit allow passing a cached
state struct to reduce rbtree search times.  clear_extent_bit
was improperly bypassing some of the checks around making sure
the extent state fields were correct for a given operation.

The fix used here (from Yan Zheng) is to use the hit_next
goto target instead of jumping all the way down to start clearing
bits without making sure the cached state was exactly correct
for the operation we were doing.

This also fixes up the setting of the start variable for both
ops in the case where we find an overlapping extent that
begins before the range we want to change.  In both cases
we were incorrectly going backwards from the original
requested change.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

We now do extra checks before a balance to make sure
there is room for the balance to take place.  One of
the checks was testing to see if we were trying to
balance away the last block group of a given type.

If there is no space available for new chunks, we
should not try and balance away the last block group
of a give type.  But, the code wasn't checking for
available chunk space, and so it was exiting too soon.

The fix here is to combine some of the checks and make
sure we try to allocate new chunks when we're balancing
the last block group.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

After a balance it is briefly possible for the space info
field in the inode to be NULL.  This adds some checks
to make sure things properly deal with the NULL value.


Signed-off-by: Chris Mason <chris.mason@oracle.com>

As we get closer to proper -ENOSPC handling in btrfs, we need more accurate
space accounting for the space info's.  Currently we exclude the free space for
the super mirrors, but the space they take up isn't accounted for in any of the
counters.  This patch introduces bytes_super, which keeps track of the amount
of bytes used for a super mirror in the block group cache and space info.  This
makes sure that our free space caclucations will be completely accurate.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

There is a slight problem with the extent entry threshold calculation for the
free space cache.  We only adjust the threshold down as we add bitmaps, but
never actually adjust the threshold up as we add bitmaps.  This means we could
fragment the free space so badly that we end up using all bitmaps to describe
the free space, use all the free space which would result in the bitmaps being
freed, but then go to add free space again as we delete things and immediately
add bitmaps since the extent threshold would still be 0.  Now as we free
bitmaps the extent threshold will be ratcheted up to allow more extent entries
to be added.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This patch removes a bunch of dead code from the snapshot removal stuff.  It
was confusing me when doing the metadata ENOSPC stuff so I killed it.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

When we first go to add free space, we allocate a new info and set the offset
and bytes to the space we are adding.  This is fine, except we actually set the
size of a bitmap as we set the bits in it, so if we add space to a bitmap, we'd
end up counting the same space twice.  This isn't a huge deal, it just makes
the allocator behave weirdly since it will think that a bitmap entry has more
space than it ends up actually having.  I used a BUG_ON() to catch when this
problem happened, and with this patch I no longer get the BUG_ON().

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The box can get locked up in the allocator if we happen upon a block group
under these conditions:

1) During a commit, so caching threads cannot make progress
2) Our block group currently is in the middle of being cached
3) Our block group currently has plenty of free space in it
4) Our block group is so fragmented that it ends up having no free space chunks
larger than min_bytes calculated by btrfs_find_space_cluster.

What happens is we try and do btrfs_find_space_cluster, which fails because it
is unable to find enough free space chunks that are large than min_bytes and
are close enough together.  Since the block group is not cached we do a
wait_block_group_cache_progress, which waits for the number of bytes we need,
except the block group already has _plenty_ of free space, its just severely
fragmented, so we loop and try again, ad infinitum.  This patch keeps us from
waiting on the block group to finish caching if we failed to find a free space
cluster before.  It also makes sure that we don't even try to find a free space
cluster if we are on our last loop in the allocator, since we will have tried
everything at this point at it is futile.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Currently, we can panic the box if the first block group we go to move is of a
type where there is no space left to move those extents.  For example, if we
fill the disk up with data, and then we try to balance and we have no room to
move the data nor room to allocate new chunks, we will panic.  Change this by
checking to see if we have room to move this chunk around, and if not, return
-ENOSPC and move on to the next chunk.  This will make sure we remove block
groups that are moveable, like if we have alot of empty metadata block groups,
and then that way we make room to be able to balance our data chunks as well.
Tested this with an fs that would panic on btrfs-vol -b normally, but no longer
panics with this patch.

V1->V2:
-actually search for a free extent on the device to make sure we can allocate a
chunk if need be.

-fix btrfs_shrink_device to make sure we actually try to relocate all the
chunks, and then if we can't return -ENOSPC so if we are doing a btrfs-vol -r
we don't remove the device with data still on it.

-check to make sure the block group we are going to relocate isn't the last one
in that particular space

-fix a bug in btrfs_shrink_device where we would change the device's size and
not fix it if we fail to do our relocate

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Fix an arithmetic error that was breaking extents cloned via the clone
ioctl starting in the second half of a file.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

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

btrfs allows subvolumes and snapshots anywhere in the directory tree.
If we snapshot a subvolume that contains a link to other subvolume
called subvolA, subvolA can be accessed through both the original
subvolume and the snapshot. This is similar to creating hard link to
directory, and has the very similar problems.

The aim of this patch is enforcing there is only one access point to
each subvolume. Only the first directory entry (the one added when
the subvolume/snapshot was created) is treated as valid access point.
The first directory entry is distinguished by checking root forward
reference. If the corresponding root forward reference is missing,
we know the entry is not the first one.

This patch also adds snapshot/subvolume rename support, the code
allows rename subvolume link across subvolumes.

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

The new back reference format does not allow reusing objectid of
deleted snapshot/subvol. So we use ++highest_objectid to allocate
objectid for new snapshot/subvol.

Now we use ++highest_objectid to allocate objectid for both new inode
and new snapshot/subvolume, so this patch removes 'find hole' code in
btrfs_find_free_objectid.

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

This patch contains two changes to avoid unnecessary tree block reads during
snapshot dropping.

First, check tree block's reference count and flags before reading the tree
block. if reference count > 1 and there is no need to update backrefs, we can
avoid reading the tree block.

Second, save when snapshot was created in root_key.offset. we can compare block
pointer's generation with snapshot's creation generation during updating
backrefs. If a given block was created before snapshot was created, the
snapshot can't be the tree block's owner. So we can avoid reading the block.

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

The allocator has some nice knobs for sending hints about where
to try and allocate new blocks, but when we're doing file allocations
we're not sending any hint at all.

This commit adds a simple extent map search to see if we can
quickly and easily find a hint for the allocator.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

When btrfs fills a delayed allocation, it tries to increase
the wbc nr_to_write to cover a big part of allocation.  The
theory is that we're doing contiguous IO and writing a few
more blocks will save seeks overall at a very low cost.

The problem is that extent_write_cache_pages could ignore
the new higher nr_to_write if nr_to_write had already gone
down to zero.  We fix that by rechecking the nr_to_write
for every page that is processed in the pagevec.

This updates the math around bumping the nr_to_write value
to make sure we don't leave a tiny amount of IO hanging
around for the very end of a new extent.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

This patch gets rid of two limitations of async block group caching.
The old code delays handling pinned extents when block group is in
caching. To allocate logged file extents, the old code need wait
until block group is fully cached. To get rid of the limitations,
This patch introduces a data structure to track the progress of
caching. Base on the caching progress, we know which extents should
be added to the free space cache when handling the pinned extents.
The logged file extents are also handled in a similar way.

This patch also changes how pinned extents are tracked. The old
code uses one tree to track pinned extents, and copy the pinned
extents tree at transaction commit time. This patch makes it use
two trees to track pinned extents. One tree for extents that are
pinned in the running transaction, one tree for extents that can
be unpinned. At transaction commit time, we swap the two trees.

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

It was possible for an async worker thread to be selected to
receive a new work item, but exit before the work item was
actually placed into that thread's work list.

This commit fixes the race by incrementing the num_pending
counter earlier, and making sure to check the number of pending
work items before a thread exits.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

The exit-on-idle code for async worker threads was incorrectly
calling spin_lock_irq with interrupts already off.

Signed-off-by: Chris Mason <chris.mason@oracle.com>