Reproduce steps:
 # mkfs.btrfs /dev/sdb5
 # mount /dev/sdb5 -o compress=lzo /mnt
 # dd if=/dev/zero of=/mnt/tmpfile bs=128K count=1
 # sync
 # truncate -s 64K /mnt/tmpfile
 root 5 inode 257 errors 400

This is because of the wrong if condition, which is used to check if we should
subtract the bytes of the dropped range from i_blocks/i_bytes of i-node or not.
When we truncate a compressed extent, btrfs substracts the bytes of the whole
extent, it's wrong. We should substract the real size that we truncate, no
matter it is a compressed extent or not. Fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

A user reported a problem where things like open with O_CREAT would take up to
30 seconds when he had nfs activity on the same mount.  This is because all of
our quick metadata operations, like create, symlink etc all do
btrfs_end_transaction_throttle, which if the transaction is blocked will wait
for the commit to complete before it returns.  This adds a ridiculous amount of
latency and isn't really needed.  The normal btrfs_end_transaction will mark the
transaction as blocked and wake the transaction kthread up if it thinks the
transaction needs to end (this being in the running out of global reserve space
scenario), and this is all that is really needed since we've already done
everything we're going to do, we just need to return.  This should help people
with the latency they were seeing when using synchronous heavy workloads.
Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Conflicts:
	fs/btrfs/ctree.h
	fs/btrfs/super.c
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Conflicts:
	fs/btrfs/volumes.c
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Recognize BTRFS_BALANCE_RESUME flag passed from userspace.  We use the
same heuristics used when recovering balance after a crash to try to
start where we left off last time.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Implement an ioctl for canceling restriper.  Currently we wait until
relocation of the current block group is finished, in future this can be
done by triggering a commit.  Balance item is deleted and no memory
about the interrupted balance is kept.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Implement an ioctl for pausing restriper.  This pauses the relocation,
but balance is still considered to be "in progress": balance item is
not deleted, other volume operations cannot be started, etc.  If paused
in the middle of profile changing operation we will continue making
allocations with the target profile.

Add a hook to close_ctree() to pause restriper and free its data
structures on unmount.  (It's safe to unmount when restriper is in
"paused" state, we will resume with the same parameters on the next
mount)
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Since restriper kthread starts involuntarily on mount and can suck cpu
and memory bandwidth add a mount option to forcefully skip it.  The
restriper in that case hangs around in paused state and can be resumed
from userspace when it's convenient.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

On mount, if balance item is found, resume balance in a separate
kernel thread.

Try to be smart to continue roughly where previous balance (or convert)
was interrupted.  For chunk types that were being converted to some
profile we turn on soft convert, in case of a simple balance we turn on
usage filter and relocate only less-than-90%-full chunks of that type.
These are just heuristics but they help quite a bit, and can be improved
in future.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Introduce a new btree objectid for storing balance item.  The reason is
to be able to resume restriper after a crash with the same parameters.
Balance item has a very high objectid and goes into tree of tree roots.

The key for the new item is as follows:

	[ BTRFS_BALANCE_OBJECTID ; BTRFS_BALANCE_ITEM_KEY ; 0 ]

Older kernels simply ignore it so it's safe to mount with an older
kernel and then go back to the newer one.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

When doing convert from one profile to another if soft mode is on
restriper won't touch chunks that already have the profile we are
converting to.  This is useful if e.g. half of the FS was converted
earlier.

The soft mode switch is (like every other filter) per-type.  This means
that we can convert for example meta chunks the "hard" way while
converting data chunks selectively with soft switch.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Profile changing is done by launching a balance with
BTRFS_BALANCE_CONVERT bits set and target fields of respective
btrfs_balance_args structs initialized.  Profile reducing code in this
case will pick restriper's target profile if it's available instead of
doing a blind reduce.  If target profile is not yet available it goes
back to a plain reduce.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Every caller of do_chunk_alloc() feeds it the reduced allocation
profile, so stop trying to reduce it one more time.  Instead check the
validity of the passed profile.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Select chunks which have at least one byte located inside a given
[vstart, vend) virtual address space range.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Select chunks which have at least one byte of at least one stripe
located on a device with devid X in a given [pstart,pend) physical
address range.

This filter only works when devid filter is turned on.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Relocate chunks which have at least one stripe located on a device with
devid X.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Select chunks that are less than X percent full.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Select chunks based on a given profile mask.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

This allows to have a separate set of filters for each chunk type
(data,meta,sys).  The code however is generic and switch on chunk type
is only done once.

This commit also adds a type filter: it allows to balance for example
meta and system chunks w/o touching data ones.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Add basic restriper infrastructure: extended balancing ioctl and all
related ioctl data structures, add data structure for tracking
restriper's state to fs_info, etc.  The semantics of the old balancing
ioctl are fully preserved.

Explicitly disallow any volume operations when balance is in progress.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Currently when new chunks are created respective avail_alloc_bits field
is updated to reflect profiles of all chunks present in the system.
However when chunks are removed profile bits are never cleared.

This patch clears profile bit of respective avail_alloc_bits field when
the last chunk with that profile is removed.  Restriper needs this to
properly operate when "downgrading".
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Right now on-disk BTRFS_BLOCK_GROUP_* profile bits are used for
avail_{data,metadata,system}_alloc_bits fields, which gather info about
available allocation profiles in the FS.  When chunk is created or read
from disk, its profile is OR'ed with the corresponding avail_alloc_bits
field.  Since SINGLE is denoted by 0 in the on-disk format, currently
there is no way to tell when such chunks become avaialble.  Restriper
needs that information, so add a separate bit for SINGLE profile.

This bit is going to be in-memory only, it should never be written out
to disk, so it's not a disk format change.  However to avoid remappings
in future, reserve corresponding on-disk bit.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Chunk's type and profile are encoded in u64 flags field.  Introduce
masks to easily access them.  Also fix the type of BTRFS_BLOCK_GROUP_*
constants, it should be ULL.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

{data,metadata,system}_alloc_profile fields have been unused for a long
time now.  Get rid of them.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

The correct lock order is uuid_mutex -> volume_mutex -> chunk_mutex,
but when we mount a filesystem which has backing seed devices, we have
this lock chain:

    open_ctree()
        lock(chunk_mutex);
        read_chunk_tree();
            read_one_dev();
                open_seed_devices();
                    lock(uuid_mutex);

and then we hit a lockdep splat.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

A bug was triggered while using seed device:

    # mkfs.btrfs /dev/loop1
    # btrfstune -S 1 /dev/loop1
    # mount -o /dev/loop1 /mnt
    # btrfs dev add /dev/loop2 /mnt

btrfs: block rsv returned -28
------------[ cut here ]------------
WARNING: at fs/btrfs/extent-tree.c:5969 btrfs_alloc_free_block+0x166/0x396 [btrfs]()
...
Call Trace:
...
[<f7b7c31c>] btrfs_cow_block+0x101/0x147 [btrfs]
[<f7b7eaa6>] btrfs_search_slot+0x1b8/0x55f [btrfs]
[<f7b7f844>] btrfs_insert_empty_items+0x42/0x7f [btrfs]
[<f7b7f8c1>] btrfs_insert_item+0x40/0x7e [btrfs]
[<f7b8ac02>] btrfs_make_block_group+0x243/0x2aa [btrfs]
[<f7bb3f53>] __btrfs_alloc_chunk+0x672/0x70e [btrfs]
[<f7bb41ff>] init_first_rw_device+0x77/0x13c [btrfs]
[<f7bb5a62>] btrfs_init_new_device+0x664/0x9fd [btrfs]
[<f7bbb65a>] btrfs_ioctl+0x694/0xdbe [btrfs]
[<c04f55f7>] do_vfs_ioctl+0x496/0x4cc
[<c04f5660>] sys_ioctl+0x33/0x4f
[<c07b9edf>] sysenter_do_call+0x12/0x38
---[ end trace 906adac595facc7d ]---

Since seed device is readonly, there's no usable space in the filesystem.
Afterwards we add a sprout device to it, and the kernel creates a METADATA
block group and a SYSTEM block group where comes free space we can reserve,
but we still get revervation failure because the global block_rsv hasn't
been updated accordingly.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

There are various bugs in block group trimming:

- It may trim from offset smaller than user-specified offset.
- It may trim beyond user-specified range.
- It may leak free space for extents smaller than specified minlen.
- It may truncate the last trimmed extent thus leak free space.
- With mixed extents+bitmaps, some extents may not be trimmed.
- With mixed extents+bitmaps, some bitmaps may not be trimmed (even
none will be trimmed). Even for those trimmed, not all the free space
in the bitmaps will be trimmed.

I rewrite btrfs_trim_block_group() and break it into two functions.
One is to trim extents only, and the other is to trim bitmaps only.

Before patching:

	# fstrim -v /mnt/
	/mnt/: 1496465408 bytes were trimmed

After patching:

	# fstrim -v /mnt/
	/mnt/: 2193768448 bytes were trimmed

And this matches the total free space:

	# btrfs fi df /mnt
	Data: total=3.58GB, used=1.79GB
	System, DUP: total=8.00MB, used=4.00KB
	System: total=4.00MB, used=0.00
	Metadata, DUP: total=205.12MB, used=97.14MB
	Metadata: total=8.00MB, used=0.00
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

For btrfs raid, while discarding a range of space, we'll need to know
the start offset and length to discard for each device, and it's done
in btrfs_map_block().

However the calculation is a bit complex for raid0 and raid10, so I
reimplement it based on a fact that:

        dev1          dev2           dev3    (raid0)
        -----------------------------------
        s0 s3 s6      s1 s4 s7       s2 s5

Each device has (total_stripes / nr_dev) stripes, or plus one.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

We pre-allocate a btrfs bio with fixed size, and then may re-allocate
memory if we find stripes are bigger than the fixed size. But this
pre-allocation is not necessary.

Also we don't have to calcuate the stripe number twice.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

Some functions never use the transaction handle passed to them.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

Check and reserve space for btrfs_update_inode().
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

We can recover from errors and return -errno to user space.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

It can return -ENOMEM.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

If we run into some failure path in io_ctl_prepare_pages(),
io_ctl->pages[] array may have some NULL pointers.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

I got this while running xfstests:

[24256.836098] block group 317849600 has an wrong amount of free space
[24256.836100] btrfs: failed to load free space cache for block group 317849600

We should clamp the extent returned by find_first_extent_bit(),
so the start of the extent won't smaller than the start of the
block group.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs into for-linus