Create an xfs_name_dot object so that upcoming scrub code can compare
against that.  Offline repair already has such an object, so we're
really just hoisting it to the kernel.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

The inode scanner tries to reduce contention on the AGI header buffer
lock by grabbing references to consecutive allocated inodes.  Batching
stops as soon as we encounter an unallocated inode.  This is unfortunate
because in the worst case performance collapses to the old "one at a
time" behavior if every other inode is free.

This is correct behavior, but we could do better.  Unallocated inodes by
definition have nothing to scan, which means the iscan can ignore them
as long as someone ensures that the scan data will reflect another
thread allocating the inode and adding interesting metadata to that
inode.  That mechanism is, of course, the live update hooks.

Therefore, extend the batching mechanism to track unallocated inodes
adjacent to the scan cursor.  The _want_live_update predicate can tell
the caller's live update hook to incorporate all live updates to what
the scanner thinks is an unallocated inode if (after dropping the AGI)
some other thread allocates one of those inodes and begins using it.

Note that we cannot just copy the ir_free bitmap into the scan cursor
because the batching stops if iget says the inode is in an intermediate
state (e.g. on the inactivation list) and cannot be igrabbed.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

After observing xfs_scrub taking forever to rebuild parent pointers on a
pptrs enabled filesystem, I decided to profile what the system was
doing.  It turns out that when there are a lot of threads trying to scan
the filesystem, most of our time is spent contending on AGI buffer
locks.  Given that we're walking the inobt records anyway, we can often
tell ahead of time when there's a bunch of (up to 64) consecutive inodes
that we could grab all at once.

Do this to amortize the cost of taking the AGI lock across as many
inodes as we possibly can.  On the author's system this seems to improve
parallel throughput from barely one and a half cores to slightly
sublinear scaling.  The obvious antipattern here of course is where the
freemask has every other bit set (e.g. all 0xA's)
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Online directory and parent repairs on parent-pointer equipped
filesystems have shown that starting a large number of parallel iscans
causes a lot of AGI buffer contention.  Try to reduce this by making it
so that iscans scan wrap around the end of the filesystem, and using a
rotor to stagger where each scanner begins.  Surprisingly, this boosts
CPU utilization (on the author's test machines) from effectively
single-threaded to 160%.  Not great, but see the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Certain types of filesystem metadata can only be checked by scanning
every file in the entire filesystem.  Specific examples of this include
quota counts, file link counts, and reverse mappings of file extents.
Directory and parent pointer reconstruction may also fall into this
category.  File scanning is much trickier than scanning AG metadata
because we have to take inode locks in the same order as the rest of
[VX]FS, we can't be holding buffer locks when we do that, and scanning
the whole filesystem takes time.

Earlier versions of the online repair patchset relied heavily on
fsfreeze as a means to quiesce the filesystem so that we could take
locks in the proper order without worrying about concurrent updates from
other writers.  Reviewers of those patches opined that freezing the
entire fs to check and repair something was not sufficiently better than
unmounting to run fsck offline.  I don't agree with that 100%, but the
message was clear: find a way to repair things that minimizes the
quiet period where nobody can write to the filesystem.

Generally, building btree indexes online can be split into two phases: a
collection phase where we compute the records that will be put into the
new btree; and a construction phase, where we construct the physical
btree blocks and persist them.  While it's simple to hold resource locks
for the entirety of the two phases to ensure that the new index is
consistent with the rest of the system, we don't need to hold resource
locks during the collection phase if we have a means to receive live
updates of other work going on elsewhere in the system.

The goal of this patch, then, is to enable online fsck to learn about
metadata updates going on in other threads while it constructs a shadow
copy of the metadata records to verify or correct the real metadata.  To
minimize the overhead when online fsck isn't running, we use srcu
notifiers because they prioritize fast access to the notifier call chain
(particularly when the chain is empty) at a cost to configuring
notifiers.  Online fsck should be relatively infrequent, so this is
acceptable.

The intended usage model is fairly simple.  Code that modifies a
metadata structure of interest should declare a xfs_hook_chain structure
in some well defined place, and call xfs_hook_call whenever an update
happens.  Online fsck code should define a struct notifier_block and use
xfs_hook_add to attach the block to the chain, along with a function to
be called.  This function should synchronize with the fsck scanner to
update whatever in-memory data the scanner is collecting.  When
finished, xfs_hook_del removes the notifier from the list and waits for
them all to complete.

Originally, I selected srcu notifiers over blocking notifiers to
implement live hooks because they seemed to have fewer impacts to
scalability.  The per-call cost of srcu_notifier_call_chain is higher
(19ns) than blocking_notifier_ (4ns) in the single threaded case, but
blocking notifiers use an rwsem to stabilize the list.  Cacheline
bouncing for that rwsem is costly to runtime code when there are a lot
of CPUs running regular filesystem operations.  If there are no hooks
installed, this is a total waste of CPU time.

Therefore, I stuck with srcu notifiers, despite trading off single
threaded performance for multithreaded performance.  I also wasn't
thrilled with the very high teardown time for srcu notifiers, since the
caller has to wait for the next rcu grace period.  This can take a long
time if there are a lot of CPUs.

Then I discovered the jump label implementation of static keys.

Jump labels use kernel code patching to replace a branch with a nop sled
when the key is disabled.  IOWs, they can eliminate the overhead of
_call_chain when there are no hooks enabled.  This makes blocking
notifiers competitive again -- scrub runs faster because teardown of the
chain is a lot cheaper, and runtime code only pays the rwsem locking
overhead when scrub is actually running.

With jump labels enabled, calls to empty notifier chains are elided from
the call sites when there are no hooks registered, which means that the
overhead is 0.36ns when fsck is not running.  This is perfect for most
of the architectures that XFS is expected to run on (e.g. x86, powerpc,
arm64, s390x, riscv).

For architectures that don't support jump labels (e.g. m68k) the runtime
overhead of checking the static key is an atomic counter read.  This
isn't great, but it's still cheaper than taking a shared rwsem.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

This patch implements a live file scanner for online fsck functions that
require the ability to walk a filesystem to gather metadata records and
stay informed about metadata changes to files that have already been
visited.

The iscan structure consists of two inode number cursors: one to track
which inode we want to visit next, and a second one to track which
inodes have already been visited.  This second cursor is key to
capturing live updates to files previously scanned while the main thread
continues scanning -- any inode greater than this value hasn't been
scanned and can go on its way; any other update must be incorporated
into the collected data.  It is critical for the scanning thraad to hold
exclusive access on the inode until after marking the inode visited.

This new code is a separate patch from the patchsets adding callers for
the sake of enabling the author to move patches around his tree with
ease.  The intended usage model for this code is roughly:

	xchk_iscan_start(iscan, 0, 0);
	while ((error = xchk_iscan_iter(sc, iscan, &ip)) == 1) {
		xfs_ilock(ip, ...);
		/* capture inode metadata */
		xchk_iscan_mark_visited(iscan, ip);
		xfs_iunlock(ip, ...);

		xfs_irele(ip);
	}
	xchk_iscan_stop(iscan);
	if (error)
		return error;

Hook functions for live updates can then do:

	if (xchk_iscan_want_live_update(...))
		/* update the captured inode metadata */
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Replace the open-coded loop that recomputes freecount with a single call
to a bit weight function.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

A data corruption problem was reported by CoreOS image builders
when using reflink based disk image copies and then converting
them to qcow2 images. The converted images failed the conversion
verification step, and it was isolated down to the fact that
qemu-img uses SEEK_HOLE/SEEK_DATA to find the data it is supposed to
copy.

The reproducer allowed me to isolate the issue down to a region of
the file that had overlapping data and COW fork extents, and the
problem was that the COW fork extent was being reported in it's
entirity by xfs_seek_iomap_begin() and so skipping over the real
data fork extents in that range.

This was somewhat hidden by the fact that 'xfs_bmap -vvp' reported
all the extents correctly, and reading the file completely (i.e. not
using seek to skip holes) would map the file correctly and all the
correct data extents are read. Hence the problem is isolated to just
the xfs_seek_iomap_begin() implementation.

Instrumentation with trace_printk made the problem obvious: we are
passing the wrong length to xfs_trim_extent() in
xfs_seek_iomap_begin(). We are passing the end_fsb, not the
maximum length of the extent we want to trim the map too. Hence the
COW extent map never gets trimmed to the start of the next data fork
extent, and so the seek code treats the entire COW fork extent as
unwritten and skips entirely over the data fork extents in that
range.

Link: https://github.com/coreos/coreos-assembler/issues/3728
Fixes: 60271ab7 ("xfs: fix SEEK_DATA for speculative COW fork preallocation")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

These functions aren't used anymore, so get rid of them.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Convert xfarray_pagesort to handle large folios by introducing a new
xfile_get_folio routine that can return a folio of arbitrary size, and
using heapsort on the full folio.  This also corrects an off-by-one bug
in the calculation of len in xfarray_pagesort that was papered over by
xfarray_want_pagesort.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfiles are shmem files, not memfds.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Now that xfile pages don't need kmapping, there is no need to cache
the kernel virtual address for them.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Add helper similar to file_{get,set}_page, but which deal with folios
and don't allocate new folio unless explicitly asked to, which map
to shmem_get_folio instead of calling into the aops.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Switch to using shmem_get_folio in xfile_load instead of using
shmem_read_mapping_page_gfp.  This gets us support for large folios
and also optimized reading from unallocated space, as
shmem_get_folio with SGP_READ won't allocate a page for them just
to zero the content.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Switch to using shmem_get_folio and manually dirtying the page instead
of abusing aops->write_begin and aops->write_end in xfile_get_page.

This simplifies the code by not doing indirect calls of not actually
exported interfaces that don't really fit the use case very well, and
happens to get us large folio support for free.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

XFS is generally used on 64-bit, non-highmem platforms and xfile
mappings are accessed all the time.  Reduce our pain by not allowing
any highmem mappings in the xfile page cache and remove all the kmap
calls for it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

shmem_read_mapping_page_gfp always returns an uptodate page or an
ERR_PTR.  Remove the code that tries to handle a non-uptodate page.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

All current and pending xfile users use the xfile_obj_load
and xfile_obj_store API, so make those the actual implementation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

vfs_getattr is needed to query inode attributes for unknown underlying
file systems.  But shmemfs is well known for users of shmem_file_setup
and shmem_read_mapping_page_gfp that rely on it not needing specific
inode revalidation and having a normal mapping.  Remove the detour
through the getattr method and an extra wrapper, and just read the
inode size and i_bytes directly in the scrub tracing code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

shmem_file_setup is explicitly intended for a file that can be
fully read and written by kernel users without restrictions.  Don't
poke into internals to change random flags in the file or inode.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

shmem_kernel_file_setup is equivalent to shmem_file_setup except that it
already sets the S_PRIVATE flag.  Use it instead of open coding the
logic.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

shmem_file_setup always returns a struct file pointer or an ERR_PTR,
so remove the code to check for a NULL return.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfile_create creates a (potentially large) sparse file.  Pass
VM_NORESERVE to shmem_file_setup to not account for the entire file size
at file creation time.
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Add a blurb that simply dirtying the folio will persist data for in-kernel
shmem files.  This is what most of the callers already do.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

XFS wants to use this for it's internal in-memory data structures and
currently duplicates the functionality.  Export shmem_kernel_file_setup
to allow XFS to switch over to using the proper kernel API.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Export shmem_get_folio as a slightly lower-level variant of
shmem_read_folio_gfp.  This will be useful for XFS xfile use cases
that want to pass SGP_NOALLOC or get a locked page, which the thin
shmem_read_folio_gfp wrapper can't provide.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Move the check that the inode really is a shmemfs one from
shmem_read_folio_gfp to shmem_get_folio_gfp given that shmem_get_folio
can also be called from outside of shmem.c.  Also turn it into a
WARN_ON_ONCE and error return instead of BUG_ON to be less severe.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Set the a_ops in shmem_symlink before reading a folio from the mapping
to prepare for asserting that shmem_get_folio is only called on shmem
mappings.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

shmem_aops really should not be exported to the world.  Move
shmem_mapping and export it as internal for the one semi-legitimate
modular user in udmabuf.

This effectively reverts commit 30e6a51d ("mm/shmem.c: make
shmem_mapping() inline"). which added a bogus shmem_aops non-GPL export
for no reason whatsoever as there as no shmem_mapping call outside of
core MM code at that point.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

mapping_set_update is only used inside mm/.  Move mapping_set_update to
mm/internal.h and turn it into an inline function instead of a macro.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Another incorrect conversion to kfree() instead of kvfree().

Fixes: 49292576 ("xfs: convert kmem_free() for kvmalloc users to kvfree()")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Wrongly converted from kmem_free() to kfree().
Reported-by: Matthew Wilcox <willy@infradead.org>
Fixes: 49292576 ("xfs: convert kmem_free() for kvmalloc users to kvfree()")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

mrlock was an rwsem wrapper that also recorded whether the lock was
held for read or write.  Now that we can ask the generic code whether
the lock is held for read or write, we can remove this wrapper and use
an rwsem directly.

As the comment says, we can't use lockdep to assert that the ILOCK is
held for write, because we might be in a workqueue, and we aren't able
to tell lockdep that we do in fact own the lock.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

To use the new rwsem_assert_held()/rwsem_assert_held_write(), we can't
use the existing ASSERT macro.  Add a new xfs_assert_ilocked() and
convert all the callers.

Fix an apparent bug in xfs_isilocked(): If the caller specifies
XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL, xfs_assert_ilocked() will check both
the IOLOCK and the ILOCK are held for write.  xfs_isilocked() only
checked that the ILOCK was held for write.

xfs_assert_ilocked() is always on, even if DEBUG or XFS_WARN aren't
defined.  It's a cheap check, so I don't think it's worth defining
it away.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Modelled after lockdep_assert_held() and lockdep_assert_held_write(),
but are always active, even when lockdep is disabled.  Of course, they
don't test that _this_ thread is the owner, but it's sufficient to catch
many bugs and doesn't incur the same performance penalty as lockdep.
Acked-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Without this the kernel crashes in kfree for files with a sufficiently
large number of extents.

Fixes: d4c75a1b ("xfs: convert remaining kmem_free() to kfree()")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

While performing the IO fault injection test, I caught the following data
corruption report:

 XFS (dm-0): Internal error ltbno + ltlen > bno at line 1957 of file fs/xfs/libxfs/xfs_alloc.c.  Caller xfs_free_ag_extent+0x79c/0x1130
 CPU: 3 PID: 33 Comm: kworker/3:0 Not tainted 6.5.0-rc7-next-20230825-00001-g7f8666926889 #214
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
 Workqueue: xfs-inodegc/dm-0 xfs_inodegc_worker
 Call Trace:
  <TASK>
  dump_stack_lvl+0x50/0x70
  xfs_corruption_error+0x134/0x150
  xfs_free_ag_extent+0x7d3/0x1130
  __xfs_free_extent+0x201/0x3c0
  xfs_trans_free_extent+0x29b/0xa10
  xfs_extent_free_finish_item+0x2a/0xb0
  xfs_defer_finish_noroll+0x8d1/0x1b40
  xfs_defer_finish+0x21/0x200
  xfs_itruncate_extents_flags+0x1cb/0x650
  xfs_free_eofblocks+0x18f/0x250
  xfs_inactive+0x485/0x570
  xfs_inodegc_worker+0x207/0x530
  process_scheduled_works+0x24a/0xe10
  worker_thread+0x5ac/0xc60
  kthread+0x2cd/0x3c0
  ret_from_fork+0x4a/0x80
  ret_from_fork_asm+0x11/0x20
  </TASK>
 XFS (dm-0): Corruption detected. Unmount and run xfs_repair

After analyzing the disk image, it was found that the corruption was
triggered by the fact that extent was recorded in both inode datafork
and AGF btree blocks. After a long time of reproduction and analysis,
we found that the reason of free sapce btree corruption was that the
AGF btree was not recovered correctly.

Consider the following situation, Checkpoint A and Checkpoint B are in
the same record and share the same start LSN1, buf items of same object
(AGF btree block) is included in both Checkpoint A and Checkpoint B. If
the buf item in Checkpoint A has been recovered and updates metadata LSN
permanently, then the buf item in Checkpoint B cannot be recovered,
because log recovery skips items with a metadata LSN >= the current LSN
of the recovery item. If there is still an inode item in Checkpoint B
that records the Extent X, the Extent X will be recorded in both inode
datafork and AGF btree block after Checkpoint B is recovered. Such
transaction can be seen when allocing enxtent for inode bmap, it record
both the addition of extent to the inode extent list and the removing
extent from the AGF.

  |------------Record (LSN1)------------------|---Record (LSN2)---|
  |-------Checkpoint A----------|----------Checkpoint B-----------|
  |     Buf Item(Extent X)      | Buf Item / Inode item(Extent X) |
  |     Extent X is freed       |     Extent X is allocated       |

After commit 12818d24 ("xfs: rework log recovery to submit buffers
on LSN boundaries") was introduced, we submit buffers on lsn boundaries
during log recovery. The above problem can be avoided under normal paths,
but it's not guaranteed under abnormal paths. Consider the following
process, if an error was encountered after recover buf item in Checkpoint
A and before recover buf item in Checkpoint B, buffers that have been
added to the buffer_list will still be submitted, this violates the
submits rule on lsn boundaries. So buf item in Checkpoint B cannot be
recovered on the next mount due to current lsn of transaction equal to
metadata lsn on disk. The detailed process of the problem is as follows.

First Mount:

  xlog_do_recovery_pass
    error = xlog_recover_process
      xlog_recover_process_data
        xlog_recover_process_ophdr
          xlog_recovery_process_trans
            ...
              /* recover buf item in Checkpoint A */
              xlog_recover_buf_commit_pass2
                xlog_recover_do_reg_buffer
                /* add buffer of agf btree block to buffer_list */
                xfs_buf_delwri_queue(bp, buffer_list)
            ...
            ==> Encounter read IO error and return
    /* submit buffers regardless of error */
    if (!list_empty(&buffer_list))
      xfs_buf_delwri_submit(&buffer_list);

    <buf items of agf btree block in Checkpoint A recovery success>

Second Mount:

  xlog_do_recovery_pass
    error = xlog_recover_process
      xlog_recover_process_data
        xlog_recover_process_ophdr
          xlog_recovery_process_trans
            ...
              /* recover buf item in Checkpoint B */
              xlog_recover_buf_commit_pass2
                /* buffer of agf btree block wouldn't added to
                   buffer_list due to lsn equal to current_lsn */
                if (XFS_LSN_CMP(lsn, current_lsn) >= 0)
                  goto out_release

    <buf items of agf btree block in Checkpoint B wouldn't recovery>

In order to make sure that submits buffers on lsn boundaries in the
abnormal paths, we need to check error status before submit buffers that
have been added from the last record processed. If error status exist,
buffers in the bufffer_list should not be writen to disk.

Canceling the buffers in the buffer_list directly isn't correct, unlike
any other place where write list was canceled, these buffers has been
initialized by xfs_buf_item_init() during recovery and held by buf item,
buf items will not be released in xfs_buf_delwri_cancel(), it's not easy
to solve.

If the filesystem has been shut down, then delwri list submission will
error out all buffers on the list via IO submission/completion and do
all the correct cleanup automatically. So shutting down the filesystem
could prevents buffers in the bufffer_list from being written to disk.

Fixes: 50d5c8d8 ("xfs: check LSN ordering for v5 superblocks during recovery")
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

when a ifdef is used in the below manner, second one could be considered as
duplicate.

ifdef DEFINE_A
...code block...
ifdef DEFINE_A
...code block...
endif
...code block...
endif

In the xfs code two such patterns were seen. Hence removing these ifdefs.
No functional change is intended here. It only aims to improve code
readability.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

While testing a 64k-blocksize filesystem, I noticed that xfs/709 fails
to rebuild the inode btree with a bunch of "Corruption remains"
messages.  It turns out that when the inode chunk size is smaller than a
single filesystem block, no block alignments constraints are necessary
for inode chunk allocations, and sb_spino_align is zero.  Hence we can
skip the check.

Fixes: dbfbf3bd ("xfs: repair inode btrees")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Noticed by inspection, simple factoring allows the same allocation
routine to be used for both transaction and recovery contexts.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>