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>

I've been seeing regular ASSERT failures in xfstests when running
fsstress based tests over the past month. xfs_getbmap() has been
failing this test:

XFS: Assertion failed: ((iflags & BMV_IF_DELALLOC) != 0) ||
(map[i].br_startblock != DELAYSTARTBLOCK), file: fs/xfs/xfs_bmap.c,
line: 5650

where it is encountering a delayed allocation extent after writing
all the dirty data to disk and then walking the extent map
atomically by holding the XFS_IOLOCK_SHARED to prevent new delayed
allocation extents from being created.

Test 083 on a 512 byte block size filesystem was used to reproduce
the problem, because it only had a 5s run timeand would usually fail
every 3-4 runs. This test is exercising ENOSPC behaviour by running
fsstress on a nearly full filesystem. The following trace extract
shows the final few events on the inode that tripped the assert:

 xfs_ilock:             flags ILOCK_EXCL caller xfs_setfilesize
 xfs_setfilesize:       isize 0x180000 disize 0x12d400 offset 0x17e200 count 7680

file size updated to 0x180000 by IO completion

 xfs_ilock:             flags ILOCK_EXCL caller xfs_iomap_write_delay
 xfs_iext_insert:       state  idx 3 offset 3072 block 4503599627239432 count 1 flag 0 caller xfs_bmap_add_extent_hole_delay
 xfs_get_blocks_alloc:  size 0x180000 offset 0x180000 count 512 type  startoff 0xc00 startblock -1 blockcount 0x1
 xfs_ilock:             flags ILOCK_EXCL caller __xfs_get_blocks

delalloc write, adding a single block at offset 0x180000

 xfs_delalloc_enospc:   isize 0x180000 disize 0x180000 offset 0x180200 count 512

ENOSPC trying to allocate a dellalloc block at offset 0x180200

 xfs_ilock:             flags ILOCK_EXCL caller xfs_iomap_write_delay
 xfs_get_blocks_alloc:  size 0x180000 offset 0x180200 count 512 type  startoff 0xc00 startblock -1 blockcount 0x2

And succeeding on retry after flushing dirty inodes.

 xfs_ilock:             flags ILOCK_EXCL caller __xfs_get_blocks
 xfs_delalloc_enospc:   isize 0x180000 disize 0x180000 offset 0x180400 count 512

ENOSPC trying to allocate a dellalloc block at offset 0x180400

 xfs_ilock:             flags ILOCK_EXCL caller xfs_iomap_write_delay
 xfs_delalloc_enospc:   isize 0x180000 disize 0x180000 offset 0x180400 count 512

And failing the retry, giving a real ENOSPC error.

 xfs_ilock:             flags ILOCK_EXCL caller xfs_vm_write_failed
                                                ^^^^^^^^^^^^^^^^^^^
The smoking gun - the write being failed and cleaning up delalloc
blocks beyond EOF allocated by the failed write.

 xfs_getattr:
 xfs_ilock:             flags IOLOCK_SHARED caller xfs_getbmap
 xfs_ilock:             flags ILOCK_SHARED caller xfs_ilock_map_shared

And that's where we died almost immediately afterwards.
xfs_bmapi_read() found delalloc extent beyond current file in memory
file size. Some debug I added to xfs_getbmap() showed the state just
before the assert failure:

 ino 0x80e48: off 0xc00, fsb 0xffffffffffffffff, len 0x1, size 0x180000
 start_fsb 0x106, end_fsb 0x638
 ino flags 0x2 nex 0xd bmvcnt 0x555, len 0x3c58a6f23c0bf1, start 0xc00
 ext 0: off 0x1fc, fsb 0x24782, len 0x254
 ext 1: off 0x450, fsb 0x40851, len 0x30
 ext 2: off 0x480, fsb 0xd99, len 0x1b8
 ext 3: off 0x92f, fsb 0x4099a, len 0x3b
 ext 4: off 0x96d, fsb 0x41844, len 0x98
 ext 5: off 0xbf1, fsb 0x408ab, len 0xf

which shows that we found a single delalloc block beyond EOF (first
line of output) when we were returning the map for a length
somewhere around 10^16 bytes long (second line), and the on-disk
extents showed they didn't go past EOF (last lines).

Further debug added to xfs_vm_write_failed() showed this happened
when punching out delalloc blocks beyond the end of the file after
the failed write:

[  132.606693] ino 0x80e48: vwf to 0x181000, sze 0x180000
[  132.609573] start_fsb 0xc01, end_fsb 0xc08

It punched the range 0xc01 -> 0xc08, but the range we really need to
punch is 0xc00 -> 0xc07 (8 blocks from 0xc00) as this testing was
run on a 512 byte block size filesystem (8 blocks per page).
the punch from is 0xc00. So end_fsb is correct, but start_fsb is
wrong as we punch from start_fsb for (end_fsb - start_fsb) blocks.
Hence we are not punching the delalloc block beyond EOF in the case.

The fix is simple - it's a silly off-by-one mistake in calculating
the range. It's especially silly because the macro used to calculate
the start_fsb already takes into account the case where the inode
size is an exact multiple of the filesystem block size...
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

For the direct IO write path, we only really need the ilock to be taken in
exclusive mode during IO submission if we need to do extent allocation
instead of all the time.

Change the block mapping code to take the ilock in shared mode for the
initial block mapping, and only retake it exclusively when we actually
have to perform extent allocations.  We were already dropping the ilock
for the transaction allocation, so this doesn't introduce new race windows.

Based on an earlier patch from Dave Chinner.
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>

Do not use unlogged metadata updates and the VFS dirty bit for updating
the file size after writeback.  In addition to causing various problems
with updates getting delayed for far too long this also drags in the
unscalable VFS dirty tracking, and is one of the few remaining unlogged
metadata updates.
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

If we convert and unwritten extent past the current i_size log the size update
as part of the extent manipulation transactions instead of doing an unlogged
metadata update later.
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

Replace xfs_ioend_new_eof with a new inline xfs_new_eof helper that
doesn't require and ioend, and is available also outside of xfs_aops.c.

Also make the code a bit more clear by using a normal if statement
instead of a slightly misleading MIN().
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

The new concurrency managed workqueues are cheap enough that we can create
per-filesystem instead of global workqueues.  This allows us to remove the
trylock or defer scheme on the ilock, which is not helpful once we have
outstanding log reservations until finishing a size update.

Also allow the default concurrency on this workqueues so that I/O completions
blocking on the ilock for one inode do not block process for another inode.
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

Now that we use the VFS i_size field throughout XFS there is no need for the
i_new_size field any more given that the VFS i_size field gets updated
in ->write_end before unlocking the page, and thus is always uptodate when
writeback could see a page.  Removing i_new_size also has the advantage that
we will never have to trim back di_size during a failed buffered write,
given that it never gets updated past i_size.

Note that currently the generic direct I/O code only updates i_size after
calling our end_io handler, which requires a small workaround to make
sure di_size actually makes it to disk.  I hope to fix this properly in
the generic code.

A downside is that we lose the support for parallel non-overlapping O_DIRECT
appending writes that recently was added.  I don't think keeping the complex
and fragile i_new_size infrastructure for this is a good tradeoff - if we
really care about parallel appending writers we should investigate turning
the iolock into a range lock, which would also allow for parallel
non-overlapping buffered writers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

There is no fundamental need to keep an in-memory inode size copy in the XFS
inode.  We already have the on-disk value in the dinode, and the separate
in-memory copy that we need for regular files only in the XFS inode.

Remove the xfs_inode i_size field and change the XFS_ISIZE macro to use the
VFS inode i_size field for regular files.  Switch code that was directly
accessing the i_size field in the xfs_inode to XFS_ISIZE, or in cases where
we are limited to regular files direct access of the VFS inode i_size field.

This also allows dropping some fairly complicated code in the write path
which dealt with keeping the xfs_inode i_size uptodate with the VFS i_size
that is getting updated inside ->write_end.

Note that we do not bother resetting the VFS i_size when truncating a file
that gets freed to zero as there is no point in doing so because the VFS inode
is no longer in use at this point.  Just relax the assert in xfs_ifree to
only check the on-disk size instead.
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBen Myers <bpm@sgi.com>

Ensure ioend->io_error gets propagated back to e.g. AIO completions.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAlex Elder <aelder@sgi.com>

Direct reclaim should never writeback pages.  For now, handle the
situation and warn about it.  Ultimately, this will be a BUG_ON.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

xfs_bmapi() currently handles both extent map reading and
allocation. As a result, the code is littered with "if (wr)"
branches to conditionally do allocation operations if required.
This makes the code much harder to follow and causes significant
indent issues with the code.

Given that read mapping is much simpler than allocation, we can
split out read mapping from xfs_bmapi() and reuse the logic that
we have already factored out do do all the hard work of handling the
extent map manipulations. The results in a much simpler function for
the common extent read operations, and will allow the allocation
code to be simplified in another commit.

Once xfs_bmapi_read() is implemented, convert all the callers of
xfs_bmapi() that are only reading extents to use the new function.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Return unwritten extent conversion errors to aio_complete.

Skip both unwritten extent conversion and size updates if we had an
I/O error or the filesystem has been shut down.

Return -EIO to the aio/buffer completion handlers in case of a
forced shutdown.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

We now have an i_dio_count filed and surrounding infrastructure to wait
for direct I/O completion instead of i_icount, and we have never needed
to iocount waits for buffered I/O given that we only set the page uptodate
after finishing all required work.  Thus remove i_iocount, and replace
the actually needed waits with calls to inode_dio_wait.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

There is no reason to queue up ioends for processing in user context
unless we actually need it.  Just complete ioends that do not convert
unwritten extents or need a size update from the end_io context.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

We really shouldn't complete AIO or DIO requests until we have finished
the unwritten extent conversion and size update.  This means fsync never
has to pick up any ioends as all work has been completed when signalling
I/O completion.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

No driver returns ENODEV from it bio completion handler, not has this
ever been documented.  Remove the dead code dealing with it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

There is a window in which the ioend that we call inode_dio_wake on
in xfs_end_io_direct_write is already free.  Fix this by storing
the inode pointer in a local variable.

This is a fix for the regression introduced in 3.1-rc by
"fs: move inode_dio_done to the end_io handler".
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Use the move from Linux 2.6 to Linux 3.x as an excuse to kill the
annoying subdirectories in the XFS source code.  Besides the large
amount of file rename the only changes are to the Makefile, a few
files including headers with the subdirectory prefix, and the binary
sysctl compat code that includes a header under fs/xfs/ from
kernel/.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

For filesystems that delay their end_io processing we should keep our
i_dio_count until the the processing is done.  Enable this by moving
the inode_dio_done call to the end_io handler if one exist.  Note that
the actual move to the workqueue for ext4 and XFS is not done in
this patch yet, but left to the filesystem maintainers.  At least
for XFS it's not needed yet either as XFS has an internal equivalent
to i_dio_count.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

For improving insight into IO completion behaviour.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

The non-blockig behaviour in xfs_vm_writepage currently is conditional on
having both the WB_SYNC_NONE sync_mode and the nonblocking flag set.
The latter used to be used by both pdflush, kswapd and a few other places
in older kernels, but has been fading out starting with the introduction
of the per-bdi flusher threads.

Enable the non-blocking behaviour for all WB_SYNC_NONE calls to get back
the behaviour we want.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

Now that we reject direct reclaim in addition to always using GFP_NOFS
allocation there's no chance we'll ever end up in ->writepage with
PF_FSTRANS set.  Add a WARN_ON if we hit this case, and stop checking
if we'd actually need to start a transaction.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAlex Elder <aelder@sgi.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

Remove two unused struct writeback_control fields:

	.encountered_congestion	(completely unused)
	.nonblocking		(never set, checked/showed in XFS,NFS/btrfs)

The .for_background check in nfs_write_inode() is also removed btw,
as .for_background implies WB_SYNC_NONE.
Reviewed-by: NJan Kara <jack@suse.cz>
Proposed-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>

Fixes generated by 'codespell' and manually reviewed.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>

With the plugging now being explicitly controlled by the
submitter, callers need not pass down unplugging hints
to the block layer. If they want to unplug, it's because they
manually plugged on their own - in which case, they should just
unplug at will.
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Convert the files in fs/xfs/linux-2.6/ to use the new xfs_<level>
logging format that replaces the old Irix inherited cmn_err()
interfaces. While there, also convert naked printk calls to use the
relevant xfs logging function to standardise output format.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NAlex Elder <aelder@sgi.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

Since the move to the new truncate sequence we call xfs_setattr to
truncate down excessively instanciated blocks.  As shown by the testcase
in kernel.org BZ #22452 that doesn't work too well.  Due to the confusion
of the internal inode size, and the VFS inode i_size it zeroes data that
it shouldn't.

But full blown truncate seems like overkill here.  We only instanciate
delayed allocations in the write path, and given that we never released
the iolock we can't have converted them to real allocations yet either.

The only nasty case is pre-existing preallocation which we need to skip.
We already do this for page discard during writeback, so make the delayed
allocation block punching a generic function and call it from the failed
write path as well as xfs_aops_discard_page. The callers are
responsible for ensuring that partial blocks are not truncated away,
and that they hold the ilock.

Based on a fix originally from Christoph Hellwig. This version used
filesystem blocks as the range unit.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

Move the buffer locking into the callers as they need to do it
wether they call xfs_map_at_offset or not.  Remove the b_bdev
assignment, which is already done by get_blocks.  Remove the
duplicate extent type asserts in xfs_convert_page just before
calling xfs_map_at_offset.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

After the last patches the code for overwrites is the same as for
delayed and unwritten extents except that it doesn't need to call
xfs_map_at_offset.  Take care of that fact to simplify
xfs_vm_writepage.

The buffer loop now first checks the type of buffer and checks/sets
the ioend type, or continues to the next buffer if it's not
interesting to us.  Only after that we validate the iomap and
perform the block mapping if needed, all in common code for the
cases where we have to do work.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

The all_bh flag is always set when entering the page clustering
machinery with a regular written extent, which means the check for
it is superflous.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

xfs_map_blocks always calls xfs_bmapi with the XFS_BMAPI_ENTIRE
entire flag, which tells it to not cap the extent at the passed in
size, but just treat the size as an minimum to map.  This means
xfs_probe_cluster is entirely useless as we'll always get the whole
extent back anyway.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

No need to lock the extent map exclusive when performing an
overwrite, we know the extent map must already have been loaded by
get_blocks.  Apply the non-blocking inode semantics to all mapping
types instead of just delayed allocations.  Remove the handling of
not yet allocated blocks for the IO_UNWRITTEN case - if an extent is
marked as unwritten allocated in the buffer it must already have an
extent on disk.

Add asserts to verify all the assumptions above in debug builds.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Opencode the xfs_iomap code in it's two callers.  The overlap of
passed flags already was minimal and will be further reduced in the
next patch.

As a side effect the BMAPI_* flags for xfs_bmapi and the IO_* flags
for I/O end processing are merged into a single set of flags, which
should be a bit more descriptive of the operation we perform.

Also improve the tracing by giving each caller it's own type set of
tracepoints.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Don't trylock the buffer.  We are the only one ever locking it for a
regular file address space, and trylock was only copied from the
generic code which did it due to the old buffer based writeout in
jbd.  Also make sure to only write out the buffer if the iomap
actually is valid, because we wouldn't have a proper mapping
otherwise.  In practice we will never get an invalid mapping here as
the page lock guarantees truncate doesn't race with us, but better
be safe than sorry.  Also make sure we allocate a new ioend when
crossing boundaries between mappings, just like we do for delalloc
and unwritten extents.  Again this currently doesn't matter as the
I/O end handler only cares for the boundaries for unwritten extents,
but this makes the code fully correct and the same as for
delalloc/unwritten extents.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

We'll never have BIO_EOPNOTSUPP set after calling submit_bio as this
can only happen for discards, and used to happen for barriers, none
of which is every submitted by xfs_submit_ioend_bio.  Also remove
the loop around bio_alloc as it will never fail due to it's mempool
backing.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Currently we only refuse a "read-only" mapping for writing out
unwritten and delayed buffers, and refuse any other for overwrites.
Improve the checks to require delalloc mappings for delayed buffers,
and unwritten extent mappings for unwritten extents.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

In commit 20cb52eb, titled
"xfs: simplify xfs_vm_writepage" I added an assert that any !mapped and
uptodate buffers are not dirty.  That asserts turns out to trigger a lot
when running fsx on filesystems with small block sizes.  The reason for
that is that the assert is simply incorrect.  !mapped and uptodate
just mean this buffer covers a hole, and whenever we do a set_page_dirty
we mark all blocks in the page dirty, no matter if they have data or
not.  So remove the assert, and update the comment above the condition
to match reality.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

This removes more dead code that was somehow missed by commit 0d99519e
(writeback: remove unused nonblocking and congestion checks).  There are
no behavior change except for the removal of two entries from one of the
ext4 tracing interface.

The nonblocking checks in ->writepages are no longer used because the
flusher now prefer to block on get_request_wait() than to skip inodes on
IO congestion.  The latter will lead to more seeky IO.

The nonblocking checks in ->writepage are no longer used because it's
redundant with the WB_SYNC_NONE check.

We no long set ->nonblocking in VM page out and page migration, because
a) it's effectively redundant with WB_SYNC_NONE in current code
b) it's old semantic of "Don't get stuck on request queues" is mis-behavior:
   that would skip some dirty inodes on congestion and page out others, which
   is unfair in terms of LRU age.

Inspired by Christoph Hellwig. Thanks!
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: David Howells <dhowells@redhat.com>
Cc: Sage Weil <sage@newdream.net>
Cc: Steve French <sfrench@samba.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>