xfs: bulkstat doesn't release AGI buffer on error

The recent refactoring of the bulkstat code left a small landmine in
the code. If a inobt read fails, then the tree walk is aborted and
returns without releasing the AGI buffer or freeing the cursor. This
can lead to a subsequent bulkstat call hanging trying to grab the
AGI buffer again.

cc: <stable@vger.kernel.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: Check error during inode btree iteration in xfs_bulkstat()

xfs_bulkstat() doesn't check error return from xfs_btree_increment(). In
case of specific fs corruption that could result in xfs_bulkstat()
entering an infinite loop because we would be looping over the same
chunk over and over again. Fix the problem by checking the return value
and terminating the loop properly.

Coverity-id: 1231338
cc: <stable@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jie Liu <jeff.u.liu@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
mm: Remove false WARN_ON from pagecache_isize_extended()

The WARN_ON checking whether i_mutex is held in
pagecache_isize_extended() was wrong because some filesystems (e.g.
XFS) use different locks for serialization of truncates / writes. So
just remove the check.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: rework zero range to prevent invalid i_size updates

The zero range operation is analogous to fallocate with the exception of
converting the range to zeroes. E.g., it attempts to allocate zeroed
blocks over the range specified by the caller. The XFS implementation
kills all delalloc blocks currently over the aligned range, converts the
range to allocated zero blocks (unwritten extents) and handles the
partial pages at the ends of the range by sending writes through the
pagecache.

The current implementation suffers from several problems associated with
inode size. If the aligned range covers an extending I/O, said I/O is
discarded and an inode size update from a previous write never makes it
to disk. Further, if an unaligned zero range extends beyond eof, the
page write induced for the partial end page can itself increase the
inode size, even if the zero range request is not supposed to update
i_size (via KEEP_SIZE, similar to an fallocate beyond EOF).

The latter behavior not only incorrectly increases the inode size, but
can lead to stray delalloc blocks on the inode. Typically, post-eof
preallocation blocks are either truncated on release or inode eviction
or explicitly written to by xfs_zero_eof() on natural file size
extension. If the inode size increases due to zero range, however,
associated blocks leak into the address space having never been
converted or mapped to pagecache pages. A direct I/O to such an
uncovered range cannot convert the extent via writeback and will BUG().
For example:

$ xfs_io -fc "pwrite 0 128k" -c "fzero -k 1m 54321" <file>
...
$ xfs_io -d -c "pread 128k 128k" <file>
<BUG>

If the entire delalloc extent happens to not have page coverage
whatsoever (e.g., delalloc conversion couldn't find a large enough free
space extent), even a full file writeback won't convert what's left of
the extent and we'll assert on inode eviction.

Rework xfs_zero_file_space() to avoid buffered I/O for partial pages.
Use the existing hole punch and prealloc mechanisms as primitives for
zero range. This implementation is not efficient nor ideal as we
writeback dirty data over the range and remove existing extents rather
than convert to unwrittern. The former writeback, however, is currently
the only mechanism available to ensure consistency between pagecache and
extent state. Even a pagecache truncate/delalloc punch prior to hole
punch has lead to inconsistencies due to racing with writeback.

This provides a consistent, correct implementation of zero range that
survives fsstress/fsx testing without assert failures. The
implementation can be optimized from this point forward once the
fundamental issue of pagecache and delalloc extent state consistency is
addressed.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
mm: Fix comment before truncate_setsize()

XFS doesn't always hold i_mutex when calling truncate_setsize() and it
uses a different lock to serialize truncates and writes. So fix the
comment before truncate_setsize().

Reported-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: bulkstat btree walk doesn't terminate

The bulkstat code has several different ways of detecting the end of
an AG when doing a walk. They are not consistently detected, and the
code that checks for the end of AG conditions is not consistently
coded. Hence the are conditions where the walk code can get stuck in
an endless loop making no progress and not triggering any
termination conditions.

Convert all the "tmp/i" status return codes from btree operations
to a common name (stat) and apply end-of-ag detection to these
operations consistently.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: bulkstat chunk formatting cursor is broken

The xfs_bulkstat_agichunk formatting cursor takes buffer values from
the main loop and passes them via the structure to the chunk
formatter, and the writes the changed values back into the main loop
local variables. Unfortunately, this complex dance is full of corner
cases that aren't handled correctly.

The biggest problem is that it is double handling the information in
both the main loop and the chunk formatting function, leading to
inconsistent updates and endless loops where progress is not made.

To fix this, push the struct xfs_bulkstat_agichunk outwards to be
the primary holder of user buffer information. this removes the
double handling in the main loop.

Also, pass the last inode processed by the chunk formatter as a
separate parameter as it purely an output variable and is not
related to the user buffer consumption cursor.

Finally, the chunk formatting code is not shared by anyone, so make
it local to xfs_itable.c.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: bulkstat chunk-formatter has issues

The loop construct has issues:
	- clustidx is completely unused, so remove it.
	- the loop tries to be smart by terminating when the
	  "freecount" tells it that all inodes are free. Just drop
	  it as in most cases we have to scan all inodes in the
	  chunk anyway.
	- move the "user buffer left" condition check to the only
	  point where we consume space int eh user buffer.
	- move the initialisation of agino out of the loop, leaving
	  just a simple loop control logic using the clusteridx.

Also, double handling of the user buffer variables leads to problems
tracking the current state - use the cursor variables directly
rather than keeping local copies and then having to update the
cursor before returning.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: bulkstat main loop logic is a mess

There are a bunch of variables tha tare more wildy scoped than they
need to be, obfuscated user buffer checks and tortured "next inode"
tracking. This all needs cleaning up to expose the real issues that
need fixing.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xfs: bulkstat error handling is broken

The error propagation is a horror - xfs_bulkstat() returns
a rval variable which is only set if there are formatter errors. Any
sort of btree walk error or corruption will cause the bulkstat walk
to terminate but will not pass an error back to userspace. Worse
is the fact that formatter errors will also be ignored if any inodes
were correctly formatted into the user buffer.

Hence bulkstat can fail badly yet still report success to userspace.
This causes significant issues with xfsdump not dumping everything
in the filesystem yet reporting success. It's not until a restore
fails that there is any indication that the dump was bad and tha
bulkstat failed. This patch now triggers xfsdump to fail with
bulkstat errors rather than silently missing files in the dump.

This now causes bulkstat to fail when the lastino cookie does not
fall inside an existing inode chunk. The pre-3.17 code tolerated
that error by allowing the code to move to the next inode chunk
as the agino target is guaranteed to fall into the next btree
record.

With the fixes up to this point in the series, xfsdump now passes on
the troublesome filesystem image that exposes all these bugs.

cc: <stable@vger.kernel.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
xfs: track bulkstat progress by agino

The bulkstat main loop progress is tracked by the "lastino"
variable, which is a full 64 bit inode. However, the loop actually
works on agno/agino pairs, and so there's a significant disconnect
between the rest of the loop and the main cursor. Convert this to
use the agino, and pass the agino into the chunk formatting function
and convert it too.

This gets rid of the inconsistency in the loop processing, and
finally makes it simple for us to skip inodes at any point in the
loop simply by incrementing the agino cursor.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Merge tag 'xfs-for-linus-3.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs

Pull xfs fixes from Dave Chinner:
 "This update fixes a warning in the new pagecache_isize_extended() and
  updates some related comments, another fix for zero-range
  misbehaviour, and an unforntuately large set of fixes for regressions
  in the bulkstat code.

  The bulkstat fixes are large but necessary.  I wouldn't normally push
  such a rework for a -rcX update, but right now xfsdump can silently
  create incomplete dumps on 3.17 and it's possible that even xfsrestore
  won't notice that the dumps were incomplete.  Hence we need to get
  this update into 3.17-stable kernels ASAP.

  In more detail, the refactoring work I committed in 3.17 has exposed a
  major hole in our QA coverage.  With both xfsdump (the major user of
  bulkstat) and xfsrestore silently ignoring missing files in the
  dump/restore process, incomplete dumps were going unnoticed if they
  were being triggered.  Many of the dump/restore filesets were so small
  that they didn't evenhave a chance of triggering the loop iteration
  bugs we introduced in 3.17, so we didn't exercise the code
  sufficiently, either.

  We have already taken steps to improve QA coverage in xfstests to
  avoid this happening again, and I've done a lot of manual verification
  of dump/restore on very large data sets (tens of millions of inodes)
  of the past week to verify this patch set results in bulkstat behaving
  the same way as it does on 3.16.

  Unfortunately, the fixes are not exactly simple - in tracking down the
  problem historic API warts were discovered (e.g xfsdump has been
  working around a 20 year old bug in the bulkstat API for the past 10
  years) and so that complicated the process of diagnosing and fixing
  the problems.  i.e. we had to fix bugs in the code as well as
  discover and re-introduce the userspace visible API bugs that we
  unwittingly "fixed" in 3.17 that xfsdump relied on to work correctly.

  Summary:

   - incorrect warnings about i_mutex locking in pagecache_isize_extended()
     and updates comments to match expected locking
   - another zero-range bug fix for stray file size updates
   - a bunch of fixes for regression in the bulkstat code introduced in
     3.17"

* tag 'xfs-for-linus-3.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs:
  xfs: track bulkstat progress by agino
  xfs: bulkstat error handling is broken
  xfs: bulkstat main loop logic is a mess
  xfs: bulkstat chunk-formatter has issues
  xfs: bulkstat chunk formatting cursor is broken
  xfs: bulkstat btree walk doesn't terminate
  mm: Fix comment before truncate_setsize()
  xfs: rework zero range to prevent invalid i_size updates
  mm: Remove false WARN_ON from pagecache_isize_extended()
  xfs: Check error during inode btree iteration in xfs_bulkstat()
  xfs: bulkstat doesn't release AGI buffer on error