Commit e459df5, 'xfs: move busy extent handling to it's own file'
moved some code from xfs_alloc.c into xfs_extent_busy.c for
convenience in userspace code merges.  One of the functions moved is
xfs_extent_busy_trim (formerly xfs_alloc_busy_trim) which is defined
STATIC.  Unfortunately this function is still used in xfs_alloc.c, and
this results in an undefined symbol in xfs.ko.

Make xfs_extent_busy_trim not static and add its prototype to
xfs_extent_busy.h.
Signed-off-by: NBen Myers <bpm@sgi.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>

Rather than specifying XBF_MAPPED for almost all buffers, introduce
XBF_UNMAPPED for the couple of users that use unmapped buffers.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

When we fail to mount the log in xfs_mountfs(), we tear down all the
infrastructure we have already allocated. However, the process of
mounting the log may have progressed to the point of reading,
caching and modifying buffers in memory. Hence before we can free
all the infrastructure, we have to flush and remove all the buffers
from memory.

Problem first reported by Eric Sandeen, later a different incarnation
was reported by Ben Myers.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

Recent event tracing during a debugging session showed that flags
that define the IO type for a buffer are leaking into the flags on
the buffer incorrectly. Fix the flag exclusion mask in
xfs_buf_alloc() to avoid problems that may be caused by such
leakage.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

With the removal of xfs_rw.h and other changes over time, xfs_bit.h
is being included in many files that don't actually need it. Clean
up the includes as necessary.

Also move the only-used-once xfs_ialloc_find_free() static inline
function out of a header file that is widely included to reduce
the number of needless dependencies on xfs_bit.h.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfs_do_force_shutdown now is the only thing in xfs_rw.c. There is no
need to keep it in it's own file anymore, so move it to xfs_fsops.c
next to xfs_fs_goingdown() and kill xfs_rw.c.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

The only thing left in xfs_rw.h is a function prototype for an inode
function.  Move that to xfs_inode.h, and kill xfs_rw.h.

Also move the function implementing the prototype from xfs_rw.c to
xfs_inode.c so we only have one function left in xfs_rw.c
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

This is the only remaining useful function in xfs_rw.h, so move it
to a header file responsible for block mapping functions that the
callers already include. Soon we can get rid of xfs_rw.h.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Now that the busy extent tracking has been moved out of the
allocation files, clean up the namespace it uses to
"xfs_extent_busy" rather than a mix of "xfs_busy" and
"xfs_alloc_busy".

Signed-off-by: Dave Chinner<dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

To make it easier to handle userspace code merges, move all the busy
extent handling out of the allocation code and into it's own file.
The userspace code does not need the busy extent code, so this
simplifies the merging of the kernel code into the userspace
xfsprogs library.

Because the busy extent code has been almost completely rewritten
over the past couple of years, also update the copyright on this new
file to include the authors that made all those changes.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Untangle the header file includes a bit by moving the definition of
xfs_agino_t to xfs_types.h. This removes the dependency that xfs_ag.h has on
xfs_inum.h, meaning we don't need to include xfs_inum.h everywhere we include
xfs_ag.h.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fsstress has a particular effective way of stopping debug XFS
kernels. We keep seeing assert failures due finding delayed
allocation extents where there should be none. This shows up when
extracting extent maps and we are holding all the locks we should be
to prevent races, so this really makes no sense to see these errors.

After checking that fsstress does not use mmap, it occurred to me
that fsstress uses something that no sane application uses - the
XFS_IOC_ALLOCSP ioctl interfaces for preallocation. These interfaces
do allocation of blocks beyond EOF without using preallocation, and
then call setattr to extend and zero the allocated blocks.

THe problem here is this is a buffered write, and hence the
allocation is a delayed allocation. Unlike the buffered IO path, the
allocation and zeroing are not serialised using the IOLOCK. Hence
the ALLOCSP operation can race with operations holding the iolock to
prevent buffered IO operations from occurring.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Just about all callers of xfs_buf_read() and xfs_buf_get() use XBF_DONTBLOCK.
This is used to make memory allocation use GFP_NOFS rather than GFP_KERNEL to
avoid recursion through memory reclaim back into the filesystem.

All the blocking get calls in growfs occur inside a transaction, even though
they are no part of the transaction, so all allocation will be GFP_NOFS due to
the task flag PF_TRANS being set. The blocking read calls occur during log
recovery, so they will probably be unaffected by converting to GFP_NOFS
allocations.

Hence make XBF_DONTBLOCK behaviour always occur for buffers and kill the flag.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfs_read_buf() is effectively the same as xfs_trans_read_buf() when called
outside a transaction context. The error handling is slightly different in that
xfs_read_buf stales the errored buffer it gets back, but there is probably good
reason for xfs_trans_read_buf() for doing this.

Hence update xfs_trans_read_buf() to the same error handling as xfs_read_buf(),
and convert all the callers of xfs_read_buf() to use the former function. We can
then remove xfs_read_buf().
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Buffers are always returned locked from the lookup routines. Hence
we don't need to tell the lookup routines to return locked buffers,
on to try and lock them. Remove XBF_LOCK from all the callers and
from internal buffer cache usage.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfs_buf_btoc and friends are simple macros that do basic block
to page index conversion and vice versa. These aren't widely used,
and we use open coded masking and shifting everywhere else. Hence
remove the macros and open code the work they do.

Also, use of PAGE_CACHE_{SIZE|SHIFT|MASK} for these macros is now
incorrect - we are using pages directly and not the page cache, so
use PAGE_{SIZE|MASK|SHIFT} instead.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Now that we pass block counts everywhere, and index buffers by block
number and length in units of blocks, convert the desired IO size
into block counts rather than bytes. Convert the code to use block
counts, and those that need byte counts get converted at the time of
use.

Rename the b_desired_count variable to something closer to it's
purpose - b_io_length - as it is only used to specify the length of
an IO for a subset of the buffer.  The only time this is used is for
log IO - both writing iclogs and during log recovery. In all other
cases, the b_io_length matches b_length, and hence a lot of code
confuses the two. e.g. the buf item code uses the io count
exclusively when it should be using the buffer length. Fix these
apprpriately as they are found.

Also, remove the XFS_BUF_{SET_}COUNT() macros that are just wrappers
around the desired IO length. They only serve to make the code
shouty loud, don't actually add any real value, and are often used
incorrectly.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Now that we pass block counts everywhere, and index buffers by block
number, track the length of the buffer in units of blocks rather
than bytes. Convert the code to use block counts, and those that
need byte counts get converted at the time of use.

Also, remove the XFS_BUF_{SET_}SIZE() macros that are just wrappers
around the buffer length. They only serve to make the code shouty
loud and don't actually add any real value.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Seeing as we pass block numbers around everywhere in the buffer
cache now, it makes no sense to index everything by byte offset.
Replace all the byte offset indexing with block number based
indexing, and replace all uses of the byte offset with direct
conversion from the block index.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

The xfs_buf_get/read API is not consistent in the units it uses, and
does not use appropriate or consistent units/types for the
variables.

Convert the API to use disk addresses and block counts for all
buffer get and read calls. Use consistent naming for all the
functions and their declarations, and convert the internal functions
to use disk addresses and block counts to avoid need to convert them
from one type to another and back again.

Fix all the callers to use disk addresses and block counts. In many
cases, this removes an additional conversion from the function call
as the callers already have a block count.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

To replace the alloc/memset pair.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Because we no longer use the page cache for buffering, there is no
direct block number to page offset relationship anymore.
xfs_buf_get_pages is still setting up b_offset as if there was some
relationship, and that is leading to incorrectly setting up
*uncached* buffers that don't overwrite b_offset once they've had
pages allocated.

For cached buffers, the first block of the buffer is always at offset
zero into the allocated memory. This is true for sub-page sized
buffers, as well as for multiple-page buffers.

For uncached buffers, b_offset is only non-zero when we are
associating specific memory to the buffers, and that is set
correctly by the code setting up the buffer.

Hence remove the setting of b_offset in xfs_buf_get_pages, because
it is now always the wrong thing to do.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

If we call xfs_buf_iowait() on a buffer that failed dispatch due to
an IO error, it will wait forever for an Io that does not exist.
This is hndled in xfs_buf_read, but there is other code that calls
xfs_buf_iowait directly that doesn't.

Rather than make the call sites have to handle checking for dispatch
errors and then checking for completion errors, make
xfs_buf_iowait() check for dispatch errors on the buffer before
waiting. This means we handle both dispatch and completion errors
with one set of error handling at the caller sites.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

When memory allocation fails to add the page array or tht epages to
a buffer during xfs_buf_get(), the buffer is left in the cache in a
partially initialised state. There is enough state left for the next
lookup on that buffer to find the buffer, and for the buffer to then
be used without finishing the initialisation.  As a result, when an
attempt to do IO on the buffer occurs, it fails with EIO because
there are no pages attached to the buffer.

We cannot remove the buffer from the cache immediately and free it,
because there may already be a racing lookup that is blocked on the
buffer lock. Hence the moment we unlock the buffer to then free it,
the other user is woken and we have a use-after-free situation.

To avoid this race condition altogether, allocate the pages for the
buffer before we insert it into the cache.  This then means that we
don't have an allocation  failure case to deal after the buffer is
already present in the cache, and hence avoid the problem
altogether.  In most cases we won't have racing inserts for the same
buffer, and so won't increase the memory pressure allocation before
insertion may entail.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfstest 229 exposes a problem with buffered IO, delayed allocation
and extent size hints. That is when we do delayed allocation during
buffered IO, we reserve space for the extent size hint alignment and
allocate the physical space to align the extent, but we do not zero
the regions of the extent that aren't written by the write(2)
syscall. The result is that we expose stale data in unwritten
regions of the extent size hints.

There are two ways to fix this. The first is to detect that we are
doing unaligned writes, check if there is already a mapping or data
over the extent size hint range, and if not zero the page cache
first before then doing the real write. This can be very expensive
for large extent size hints, especially if the subsequent writes
fill then entire extent size before the data is written to disk.

The second, and simpler way, is simply to turn off delayed
allocation when the extent size hint is set and use preallocation
instead. This results in unwritten extents being laid down on disk
and so only the written portions will be converted. This matches the
behaviour for direct IO, and will also work for the real time
device. The disadvantage of this approach is that for small extent
size hints we can get file fragmentation, but in general extent size
hints are fairly large (e.g. stripe width sized) so this isn't a big
deal.

Implement the second approach as it is simple and effective.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Speculative delayed allocation beyond EOF near the maximum supported
file offset can result in creating delalloc extents beyond
mp->m_maxioffset (8EB). These can never be trimmed during
xfs_free_eof_blocks() because they are beyond mp->m_maxioffset, and
that results in assert failures in xfs_fs_destroy_inode() due to
delalloc blocks still being present. xfstests 071 exposes this
problem.

Limit speculative delalloc to mp->m_maxioffset to avoid this
problem.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

When we are doing speculative delayed allocation beyond EOF,
conversion of the region allocated beyond EOF is dependent on the
largest free space extent available. If the largest free extent is
smaller than the delalloc range, then after allocation we leave
a delalloc extent that starts beyond EOF. This extent cannot *ever*
be converted by flushing data, and so will remain there until either
the EOF moves into the extent or it is truncated away.

Hence if xfs_getbmap() runs on such an inode and is asked to return
extents beyond EOF, it will assert fail on this extent even though
there is nothing xfs_getbmap() can do to convert it to a real
extent. Hence we should simply report these delalloc extents rather
than assert that there should be none.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Often mounting small filesystem with small logs will emit a warning
such as:

XFS (vdb): Invalid block length (0x2000) for buffer

during log recovery. This causes tests to randomly fail because this
output causes the clean filesystem checks on test completion to
think the filesystem is inconsistent.

The cause of the error is simply that log recovery is asking for a
buffer size that is larger than the log when zeroing the tail. This
is because the buffer size is rounded up, and if the right head and
tail conditions exist then the buffer size can be larger than the log.
Limit the variable size xlog_get_bp() callers to requesting buffers
smaller than the log.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

When a partial write inside EOF fails, it can leave delayed
allocation blocks lying around because they don't get punched back
out. This leads to assert failures like:

XFS: Assertion failed: XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0, file: fs/xfs/xfs_super.c, line: 847

when evicting inodes from the cache. This can be trivially triggered
by xfstests 083, which takes between 5 and 15 executions on a 512
byte block size filesystem to trip over this. Debugging shows a
failed write due to ENOSPC calling xfs_vm_write_failed such as:

[ 5012.329024] ino 0xa0026: vwf to 0x17000, sze 0x1c85ae

and no action is taken on it. This leaves behind a delayed
allocation extent that has no page covering it and no data in it:

[ 5015.867162] ino 0xa0026: blks: 0x83 delay blocks 0x1, size 0x2538c0
[ 5015.868293] ext 0: off 0x4a, fsb 0x50306, len 0x1
[ 5015.869095] ext 1: off 0x4b, fsb 0x7899, len 0x6b
[ 5015.869900] ext 2: off 0xb6, fsb 0xffffffffe0008, len 0x1
                                    ^^^^^^^^^^^^^^^
[ 5015.871027] ext 3: off 0x36e, fsb 0x7a27, len 0xd
[ 5015.872206] ext 4: off 0x4cf, fsb 0x7a1d, len 0xa

So the delayed allocation extent is one block long at offset
0x16c00. Tracing shows that a bigger write:

xfs_file_buffered_write: size 0x1c85ae offset 0x959d count 0x1ca3f ioflags

allocates the block, and then fails with ENOSPC trying to allocate
the last block on the page, leading to a failed write with stale
delalloc blocks on it.

Because we've had an ENOSPC when trying to allocate 0x16e00, it
means that we are never goinge to call ->write_end on the page and
so the allocated new buffer will not get marked dirty or have the
buffer_new state cleared. In other works, what the above write is
supposed to end up with is this mapping for the page:

    +------+------+------+------+------+------+------+------+
      UMA    UMA    UMA    UMA    UMA    UMA    UND    FAIL

where:  U = uptodate
        M = mapped
        N = new
        A = allocated
        D = delalloc
        FAIL = block we ENOSPC'd on.

and the key point being the buffer_new() state for the newly
allocated delayed allocation block. Except it doesn't - we're not
marking buffers new correctly.

That buffer_new() problem goes back to the xfs_iomap removal days,
where xfs_iomap() used to return a "new" status for any map with
newly allocated blocks, so that __xfs_get_blocks() could call
set_buffer_new() on it. We still have the "new" variable and the
check for it in the set_buffer_new() logic - except we never set it
now!

Hence that newly allocated delalloc block doesn't have the new flag
set on it, so when the write fails we cannot tell which blocks we
are supposed to punch out. WHy do we need the buffer_new flag? Well,
that's because we can have this case:

    +------+------+------+------+------+------+------+------+
      UMD    UMD    UMD    UMD    UMD    UMD    UND    FAIL

where all the UMD buffers contain valid data from a previously
successful write() system call. We only want to punch the UND buffer
because that's the only one that we added in this write and it was
only this write that failed.

That implies that even the old buffer_new() logic was wrong -
because it would result in all those UMD buffers on the page having
set_buffer_new() called on them even though they aren't new. Hence
we shoul donly be calling set_buffer_new() for delalloc buffers that
were allocated (i.e. were a hole before xfs_iomap_write_delay() was
called).

So, fix this set_buffer_new logic according to how we need it to
work for handling failed writes correctly. Also, restore the new
buffer logic handling for blocks allocated via
xfs_iomap_write_direct(), because it should still set the buffer_new
flag appropriately for newly allocated blocks, too.

SO, now we have the buffer_new() being set appropriately in
__xfs_get_blocks(), we can detect the exact delalloc ranges that
we allocated in a failed write, and hence can now do a walk of the
buffers on a page to find them.

Except, it's not that easy. When block_write_begin() fails, it
unlocks and releases the page that we just had an error on, so we
can't use that page to handle errors anymore. We have to get access
to the page while it is still locked to walk the buffers. Hence we
have to open code block_write_begin() in xfs_vm_write_begin() to be
able to insert xfs_vm_write_failed() is the right place.

With that, we can pass the page and write range to
xfs_vm_write_failed() and walk the buffers on the page, looking for
delalloc buffers that are either new or beyond EOF and punch them
out. Handling buffers beyond EOF ensures we still handle the
existing case that xfs_vm_write_failed() handles.

Of special note is the truncate_pagecache() handling - that only
should be done for pages outside EOF - pages within EOF can still
contain valid, dirty data so we must not punch them out of the
cache.

That just leaves the xfs_vm_write_end() failure handling.
The only failure case here is that we didn't copy the entire range,
and generic_write_end() handles that by zeroing the region of the
page that wasn't copied, we don't have to punch out blocks within
the file because they are guaranteed to contain zeros. Hence we only
have to handle the existing "beyond EOF" case and don't need access
to the buffers on the page. Hence it remains largely unchanged.

Note that xfs_getbmap() can still trip over delalloc blocks beyond
EOF that are left there by speculative delayed allocation. Hence
this bug fix does not solve all known issues with bmap vs delalloc,
but it does fix all the the known accidental occurances of the
problem.
Signed-off-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfs_is_delayed_page() checks to see if a page has buffers matching
the given IO type passed in. It does so by walking the buffer heads
on the page and checking if the state flags match the IO type.

However, the "acceptable" variable that is calculated is overwritten
every time a new buffer is checked. Hence if the first buffer on the
page is of the right type, this state is lost if the second buffer
is not of the correct type. This means that xfs_aops_discard_page()
may not discard delalloc regions when it is supposed to, and
xfs_convert_page() may not cluster IO as efficiently as possible.

This problem only occurs on filesystems with a block size smaller
than page size.

Also, rename xfs_is_delayed_page() to xfs_check_page_type() to
better describe what it is doing - it is not delalloc specific
anymore.

The problem was first noticed by Peter Watkins.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Doing background CIL flushes adds significant latency to whatever
async transaction that triggers it. To avoid blocking async
transactions on things like waiting for log buffer IO to complete,
move the CIL push off into a workqueue.  By moving the push work
into a workqueue, we remove all the latency that the commit adds
from the foreground transaction commit path. This also means that
single threaded workloads won't do the CIL push procssing, leaving
them more CPU to do more async transactions.

To do this, we need to keep track of the sequence number we have
pushed work for. This avoids having many transaction commits
attempting to schedule work for the same sequence, and ensures that
we only ever have one push (background or forced) in progress at a
time. It also means that we don't need to take the CIL lock in write
mode to check for potential background push races, which reduces
lock contention.

To avoid potential issues with "smart" IO schedulers, don't use the
workqueue for log force triggered flushes. Instead, do them directly
so that the log IO is done directly by the process issuing the log
force and so doesn't get stuck on IO elevator queue idling
incorrectly delaying the log IO from the workqueue.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

xfs_trans_ail_delete_bulk() can be called from different contexts so
if the item is not in the AIL we need different shutdown for each
context.  Pass in the shutdown method needed so the correct action
can be taken.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Queue delwri buffers on a local on-stack list instead of a per-buftarg one,
and write back the buffers per-process instead of by waking up xfsbufd.

This is now easily doable given that we have very few places left that write
delwri buffers:

 - log recovery:
	Only done at mount time, and already forcing out the buffers
	synchronously using xfs_flush_buftarg

 - quotacheck:
	Same story.

 - dquot reclaim:
	Writes out dirty dquots on the LRU under memory pressure.  We might
	want to look into doing more of this via xfsaild, but it's already
	more optimal than the synchronous inode reclaim that writes each
	buffer synchronously.

 - xfsaild:
	This is the main beneficiary of the change.  By keeping a local list
	of buffers to write we reduce latency of writing out buffers, and
	more importably we can remove all the delwri list promotions which
	were hitting the buffer cache hard under sustained metadata loads.

The implementation is very straight forward - xfs_buf_delwri_queue now gets
a new list_head pointer that it adds the delwri buffers to, and all callers
need to eventually submit the list using xfs_buf_delwi_submit or
xfs_buf_delwi_submit_nowait.  Buffers that already are on a delwri list are
skipped in xfs_buf_delwri_queue, assuming they already are on another delwri
list.  The biggest change to pass down the buffer list was done to the AIL
pushing. Now that we operate on buffers the trylock, push and pushbuf log
item methods are merged into a single push routine, which tries to lock the
item, and if possible add the buffer that needs writeback to the buffer list.
This leads to much simpler code than the previous split but requires the
individual IOP_PUSH instances to unlock and reacquire the AIL around calls
to blocking routines.

Given that xfsailds now also handle writing out buffers, the conditions for
log forcing and the sleep times needed some small changes.  The most
important one is that we consider an AIL busy as long we still have buffers
to push, and the other one is that we do increment the pushed LSN for
buffers that are under flushing at this moment, but still count them towards
the stuck items for restart purposes.  Without this we could hammer on stuck
items without ever forcing the log and not make progress under heavy random
delete workloads on fast flash storage devices.

[ Dave Chinner:
	- rebase on previous patches.
	- improved comments for XBF_DELWRI_Q handling
	- fix XBF_ASYNC handling in queue submission (test 106 failure)
	- rename delwri submit function buffer list parameters for clarity
	- xfs_efd_item_push() should return XFS_ITEM_PINNED ]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Instead of adding buffers to the delwri list as soon as they are logged,
even if they can't be written until commited because they are pinned
defer adding them to the delwri list until xfsaild pushes them.  This
makes the code more similar to other log items and prepares for writing
buffers directly from xfsaild.

The complication here is that we need to fail buffers that were added
but not logged yet in xfs_buf_item_unpin, borrowing code from
xfs_bioerror.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Instead of writing the buffer directly from inside xfs_qm_dqflush return it
to the caller and let the caller decide what to do with the buffer.  Also
remove the pincount check in xfs_qm_dqflush that all non-blocking callers
already implement and the now unused flags parameter and the XFS_DQ_IS_DIRTY
check that all callers already perform.

[ Dave Chinner: fixed build error cause by missing '{'. ]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Instead of writing the buffer directly from inside xfs_iflush return it to
the caller and let the caller decide what to do with the buffer.  Also
remove the pincount check in xfs_iflush that all non-blocking callers already
implement and the now unused flags parameter.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

We already flush dirty inodes throug the AIL regularly, there is no reason
to have second thread compete with it and disturb the I/O pattern.  We still
do write inodes when doing a synchronous reclaim from the shrinker or during
unmount for now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Now that we write back all metadata either synchronously or through
the AIL we can simply implement metadata freezing in terms of
emptying the AIL.

The implementation for this is fairly simply and straight-forward:
A new routine is added that asks the xfsaild to push the AIL to the
end and waits for it to complete and send a wakeup. The routine will
then loop if the AIL is not actually empty, and continue to do so
until the AIL is compeltely empty.

We keep an inode reclaim pass in the freeze process to avoid having
memory pressure have to reclaim inodes that require dirtying the
filesystem to be reclaimed after the freeze has completed. This
means we can also treat unmount in the exact same way as freeze.

As an upside we can now remove the radix tree based inode writeback
and xfs_unmountfs_writesb.

[ Dave Chinner:
	- Cleaned up commit message.
	- Added inode reclaim passes back into freeze.
	- Cleaned up wakeup mechanism to avoid the use of a new
	  sleep counter variable. ]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Provide a variant of xlog_assign_tail_lsn that has the AIL lock already
held.  By doing so we do an additional atomic_read + atomic_set under
the lock, which comes down to two instructions.

Switch xfs_trans_ail_update_bulk and xfs_trans_ail_delete_bulk to the
new version to reduce the number of lock roundtrips, and prepare for
a new addition that would require a third lock roundtrip in
xfs_trans_ail_delete_bulk.  This addition is also the reason for
slightly rearranging the conditionals and relying on xfs_log_space_wake
for checking that the filesystem has been shut down internally.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>