When extent needs to be split, btrfs_mark_extent_written truncates the extent
first, then inserts a new extent and increases the reference count.

The race happens if someone else deletes the old extent before the new extent
is inserted. The fix here is increase the reference count in advance. This race
is similar to the race in btrfs_drop_extents that was recently fixed.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

Seed device is a special btrfs with SEEDING super flag
set and can only be mounted in read-only mode. Seed
devices allow people to create new btrfs on top of it.

The new FS contains the same contents as the seed device,
but it can be mounted in read-write mode.

This patch does the following:

1) split code in btrfs_alloc_chunk into two parts. The first part does makes
the newly allocated chunk usable, but does not do any operation that modifies
the chunk tree. The second part does the the chunk tree modifications. This
division is for the bootstrap step of adding storage to the seed device.

2) Update device management code to handle seed device.
The basic idea is: For an FS grown from seed devices, its
seed devices are put into a list. Seed devices are
opened on demand at mounting time. If any seed device is
missing or has been changed, btrfs kernel module will
refuse to mount the FS.

3) make btrfs_find_block_group not return NULL when all
block groups are read-only.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

This patch adds mount ro and remount support. The main
changes in patch are: adding btrfs_remount and related
helper function; splitting the transaction related code
out of close_ctree into btrfs_commit_super; updating
allocator to properly handle read only block group.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

While profiling the allocator I noticed a good amount of time was being spent in
finish_current_insert and del_pending_extents, and as the filesystem filled up
more and more time was being spent in those functions.  This patch aims to try
and reduce that problem.  This happens two ways

1) track if we tried to delete an extent that we are going to update or insert.
Once we get into finish_current_insert we discard any of the extents that were
marked for deletion.  This saves us from doing unnecessary work almost every
time finish_current_insert runs.

2) Batch insertion/updates/deletions.  Instead of doing a btrfs_search_slot for
each individual extent and doing the needed operation, we instead keep the leaf
around and see if there is anything else we can do on that leaf.  On the insert
case I introduced a btrfs_insert_some_items, which will take an array of keys
with an array of data_sizes and try and squeeze in as many of those keys as
possible, and then return how many keys it was able to insert.  In the update
case we search for an extent ref, update the ref and then loop through the leaf
to see if any of the other refs we are looking to update are on that leaf, and
then once we are done we release the path and search for the next ref we need to
update.  And finally for the deletion we try and delete the extent+ref in pairs,
so we will try to find extent+ref pairs next to the extent we are trying to free
and free them in bulk if possible.

This along with the other cluster fix that Chris pushed out a bit ago helps make
the allocator preform more uniformly as it fills up the disk.  There is still a
slight drop as we fill up the disk since we start having to stick new blocks in
odd places which results in more COW's than on a empty fs, but the drop is not
nearly as severe as it was before.
Signed-off-by: Josef Bacik <jbacik@redhat.com>

This patch adds an additional CLONE_RANGE ioctl to clone an arbitrary 
(block-aligned) file range to another file.  The original CLONE ioctl 
becomes a special case of cloning the entire file range.  The logic is a 
bit more complex now since ranges may be cloned to different offsets, and 
because we may only be cloning the beginning or end of a particular extent 
or checksum item.

An additional sanity check ensures the source and destination files aren't 
the same (which would previously deadlock), although eventually this could 
be extended to allow the duplication of file data at a different offset 
within the same file.

Any extents within the destination range in the target file are dropped.

We currently do not cope with the case where a compressed inline extent 
needs to be split.  This will probably require decompressing the extent 
into a temporary address_space, and inserting just the cloned portion as a 
new compressed inline extent.  For now, just return -EINVAL in this case.  
Note that this never comes up in the more common case of cloning an entire 
file.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

When we fail to allocate a new block group, we should still do the
checks to make sure allocations try again with the minimum requested
allocation size.

This also fixes a deadlock that come from a missed down_read in
the chunk allocation failure handling.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This fixes latency problems on metadata reads by making sure they
don't go through the async submit queue, and by tuning down the amount
of readahead done during btree searches.

Also, the btrfs bdi congestion function is tuned to ignore the
number of pending async bios and checksums pending.  There is additional
code that throttles new async bios now and the congestion function
doesn't need to worry about it anymore.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Simple casting here and there to fix things up.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

btrfs_drop_extents will drop paths and search again when it needs to
force COW of higher nodes.  It was using the key it found during the last
search as the offset for the next search.

But, this wasn't always correct.  The key could be from before our desired
range, and because we're dropping the path, it is possible for file's items
to change while we do the search again.

The fix here is to make sure we don't search for something smaller than
the offset btrfs_drop_extents was called with.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The allocator wasn't catching all of the cases where it needed to do
extra loops because the check to enforce them wasn't happening early
enough.

When the allocator decided to increase the size of the allocation
for metadata clustering, it wasn't always setting the empty_size to
include the extra (optional) bytes.  This also fixes the empty_size field
to be correct.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

When btrfs unplugs, it tries to find the correct device to unplug
via search through the extent_map tree.  This avoids unplugging
a device that doesn't need it, but is a waste of time for filesystems
with a small number of devices.

This patch checks the total number of devices before doing the
search.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The extent_io.c code has a #define to find and cleanup extent state leaks
on module unmount.  This adds a very highly contended spinlock to a
hot path for most FS operations.

Turn it off by default.  A later changeset will add a .config option
for it.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This makes sure the orig_start field in struct extent_map gets set
everywhere the extent_map structs are created or modified.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

With all the recent fixes to the delalloc locking, it is now safe
again to use invalidatepage inside the writepage code for
pages outside of i_size.  This used to deadlock against some of the
code to write locked ranges of pages, but all of that has been fixed.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The loop searching for free space would exit out too soon when
metadata clustering was trying to allocate a large extent.  This makes
sure a full scan of the free space is done searching for only the
minimum extent size requested by the higher layers.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Yan's fix to use the correct file offset during compressed reads used the
extent_map struct pointer after it had been freed.  This saves the
fields we want for later use instead.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The decompress code doesn't take the logical offset in extent
pointer into account. If the logical offset isn't zero, data
will be decompressed into wrong pages.

The solution used here is to record the starting offset of the extent
in the file separately from the logical start of the extent_map struct.
This allows us to avoid problems inserting overlapping extents.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

This adds a PageDirty check to the writeback path that locks pages
for delalloc.  If a page wasn't dirty at this point, it is in the
process of being truncated away.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

When metadata allocation clustering has to fall back to unclustered
allocs because large free areas could not be found, it was sometimes
substracting too much from the total bytes to allocate.  This would
make it wrap below zero.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

While doing a commit, btrfs makes sure all the metadata blocks
were properly written to disk, calling wait_on_page_writeback for
each page.  This writeback happens after allowing another transaction
to start, so it competes for the disk with other processes in the FS.

If the page writeback bit is still set, each wait_on_page_writeback might
trigger an unplug, even though the page might be waiting for checksumming
to finish or might be waiting for the async work queue to submit the
bio.

This trades wait_on_page_writeback for waiting on the extent writeback
bits.  It won't trigger any unplugs and substantially improves performance
in a number of workloads.

This also changes the async bio submission to avoid requeueing if there
is only one device.  The requeue just wastes CPU time because there are
no other devices to service.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

In comes cases the empty cluster was added twice to the total number of
bytes the allocator was trying to find.

With empty clustering on, the hint byte was sometimes outside of the
block group.  Add an extra goto to find the correct block group.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

When writing a compressed extent, a number of bios are created that
point to a single struct compressed_bio.  At end_io time an atomic counter in
the compressed_bio struct makes sure that all of the bios have finished
before final end_io processing is done.

But when multiple bios are needed to write a compressed extent, the
counter was being incremented after the first bio was sent to submit_bio.
It is possible the bio will complete before the counter is incremented,
making the end_io handler free the compressed_bio struct before
processing is finished.

The fix is to increment the atomic counter before bio submission,
both for compressed reads and writes.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This lowers the empty cluster target for metadata allocations.  The lower
target makes it easier to do allocations and still seems to perform well.

It also fixes the allocator loop to drop the empty cluster when things
start getting difficult, avoiding false enospc warnings.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The allocator uses the last allocation as a starting point for metadata
allocations, and tries to allocate in clusters of at least 256k.

If the search for a free block fails to find the expected block, this patch
forces a new cluster to be found in the free list.
Signed-off-by: Chris Mason <chris.mason@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>

Btrfs uses kernel threads to create async work queues for cpu intensive
operations such as checksumming and decompression.  These work well,
but they make it difficult to keep IO order intact.

A single writepages call from pdflush or fsync will turn into a number
of bios, and each bio is checksummed in parallel.  Once the checksum is
computed, the bio is sent down to the disk, and since we don't control
the order in which the parallel operations happen, they might go down to
the disk in almost any order.

The code deals with this somewhat by having deep work queues for a single
kernel thread, making it very likely that a single thread will process all
the bios for a single inode.

This patch introduces an explicitly ordered work queue.  As work structs
are placed into the queue they are put onto the tail of a list.  They have
three callbacks:

->func (cpu intensive processing here)
->ordered_func (order sensitive processing here)
->ordered_free (free the work struct, all processing is done)

The work struct has three callbacks.  The func callback does the cpu intensive
work, and when it completes the work struct is marked as done.

Every time a work struct completes, the list is checked to see if the head
is marked as done.  If so the ordered_func callback is used to do the
order sensitive processing and the ordered_free callback is used to do
any cleanup.  Then we loop back and check the head of the list again.

This patch also changes the checksumming code to use the ordered workqueues.
One a 4 drive array, it increases streaming writes from 280MB/s to 350MB/s.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

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

Make sure we keep page->mapping NULL on the pages we're getting
via alloc_page.  It gets set so a few of the callbacks can do the right
thing, but in general these pages don't have a mapping.

Don't try to truncate compressed inline items in btrfs_drop_extents.
The whole compressed item must be preserved.

Don't try to create multipage inline compressed items.  When we try to
overwrite just the first page of the file, we would have to read in and recow
all the pages after it in the same compressed inline items.  For now, only
create single page inline items.

Make sure we lock pages in the correct order during delalloc.  The
search into the state tree for delalloc bytes can return bytes before
the page we already have locked.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This patch updates btrfs-progs for fallocate support.

fallocate is a little different in Btrfs because we need to tell the
COW system that a given preallocated extent doesn't need to be
cow'd as long as there are no snapshots of it.  This leverages the
-o nodatacow checks.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

This patch simplifies the nodatacow checker. If all references
were created after the latest snapshot, then we can avoid COW
safely. This patch also updates run_delalloc_nocow to do more
fine-grained checking.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

When dropping middle part of an extent, btrfs_drop_extents truncates
the extent at first, then inserts a bookend extent.

Since truncation and insertion can't be done atomically, there is a small
period that the bookend extent isn't in the tree. This causes problem for
functions that search the tree for file extent item. The way to fix this is
lock the range of the bookend extent before truncation.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

This patch splits the hole insertion code out of btrfs_setattr
into btrfs_cont_expand and updates btrfs_get_extent to properly
handle the case that file extent items are not continuous.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

When compression was on, we were improperly ignoring -o nodatasum.  This
reworks the logic a bit to properly honor all the flags.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

The byte walk counting was awkward and error prone.  This uses the
number of pages sent the higher layer to build bios.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

finish_current_insert and del_pending_extents process extent tree modifications
that build up while we are changing the extent tree.  It is a confusing
bit of code that prevents recursion.

Both functions run through a list of pending operations and both funcs
add to the list of pending operations.  If you have two procs in either
one of them, they can end up looping forever making more work for each other.

This patch makes them walk forward through the list of pending changes instead
of always trying to process the entire list.  At transaction commit
time, we catch any changes that were left over.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

This patch adds transaction IDs to root tree pointers.
Transaction IDs in tree pointers are compared with the
generation numbers in block headers when reading root
blocks of trees. This can detect some types of IO errors.
Signed-off-by: Yan Zheng <zheng.yan@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>

So there is an odd case where we can possibly return -ENOSPC when there is in
fact space to be had.  It only happens with Metadata writes, and happens _very_
infrequently.  What has to happen is we have to allocate have allocated out of
the first logical byte on the disk, which would set last_alloc to
first_logical_byte(root, 0), so search_start == orig_search_start.  We then
need to allocate for normal metadata, so BTRFS_BLOCK_GROUP_METADATA |
BTRFS_BLOCK_GROUP_DUP.  We will do a block lookup for the given search_start,
block_group_bits() won't match and we'll go to choose another block group.
However because search_start matches orig_search_start we go to see if we can
allocate a chunk.

If we are in the situation that we cannot allocate a chunk, we fail and ENOSPC.
This is kind of a big flaw of the way find_free_extent works, as it along with
find_free_space loop through _all_ of the block groups, not just the ones that
we want to allocate out of.  This patch completely kills find_free_space and
rolls it into find_free_extent.  I've introduced a sort of state machine into
this, which will make it easier to get cache miss information out of the
allocator, and will work well with my locking changes.

The basic flow is this:  We have the variable loop which is 0, meaning we are
in the hint phase.  We lookup the block group for the hint, and lookup the
space_info for what we want to allocate out of.  If the block group we were
pointed at by the hint either isn't of the correct type, or just doesn't have
the space we need, we set head to space_info->block_groups, so we start at the
beginning of the block groups for this particular space info, and loop through.

This is also where we add the empty_cluster to total_needed.  At this point
loop is set to 1 and we just loop through all of the block groups for this
particular space_info looking for the space we need, just as find_free_space
would have done, except we only hit the block groups we want and not _all_ of
the block groups.  If we come full circle we see if we can allocate a chunk.
If we cannot of course we exit with -ENOSPC and we are good.  If not we start
over at space_info->block_groups and loop through again, with loop == 2.  If we
come full circle and haven't found what we need then we exit with -ENOSPC.
I've been running this for a couple of days now and it seems stable, and I
haven't yet hit a -ENOSPC when there was plenty of space left.

Also I've made a groups_sem to handle the group list for the space_info.  This
is part of my locking changes, but is relatively safe and seems better than
holding the space_info spinlock over that entire search time.  Thanks,
Signed-off-by: Josef Bacik <jbacik@redhat.com>
 

This patch improves the space balancing code to keep more sharing
of tree blocks. The only case that breaks sharing of tree blocks is
data extents get fragmented during balancing. The main changes in
this patch are:

Add a 'drop sub-tree' function. This solves the problem in old code
that BTRFS_HEADER_FLAG_WRITTEN check breaks sharing of tree block.

Remove relocation mapping tree. Relocation mappings are stored in
struct btrfs_ref_path and updated dynamically during walking up/down
the reference path. This reduces CPU usage and simplifies code.

This patch also fixes a bug. Root items for reloc trees should be
updated in btrfs_free_reloc_root.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>