Darrick J. Wong [Thu, 22 Feb 2024 20:43:40 +0000 (12:43 -0800)]
xfs: define an in-memory btree for storing refcount bag info during repairs
Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:
It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.
So we add the first rmap to the rcbag, and it looks like:
0: {agbno: 10, length: 40}
The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:
The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:
The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.
That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.
I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.
(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:40 +0000 (12:43 -0800)]
xfs: hook live rmap operations during a repair operation
Hook the regular rmap code when an rmapbt repair operation is running so
that we can unlock the AGF buffer to scan the filesystem and keep the
in-memory btree up to date during the scan.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:38 +0000 (12:43 -0800)]
xfs: repair the rmapbt
Rebuild the reverse mapping btree from all primary metadata. This first
patch establishes the bare mechanics of finding records and putting
together a new ondisk tree; more complex pieces are needed to make it
work properly.
Link: Documentation/filesystems/xfs-online-fsck-design.rst Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:37 +0000 (12:43 -0800)]
xfs: create agblock bitmap helper to count the number of set regions
In the next patch, the rmap btree repair code will need to estimate the
size of the new ondisk rmapbt. The size is a function of the number of
records that will be written to disk, and the size of the recordset is
the number of observations made while scanning the filesystem plus the
number of OWN_AG records that will be injected into the rmap btree.
OWN_AG rmap records track the free space btrees, the AGFL, and the new
rmap btree itself. The repair tool uses a bitmap to record the space
used for all four structures, which is why we need a function to count
the number of set regions.
A reviewer requested that this be pulled into a separate patch with its
own justification, so here it is.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:36 +0000 (12:43 -0800)]
xfs: launder in-memory btree buffers before transaction commit
As we've noted in various places, all current users of in-memory btrees
are online fsck. Online fsck only stages a btree long enough to rebuild
an ondisk data structure, which means that the in-memory btree is
ephemeral. Furthermore, if we encounter /any/ errors while updating an
in-memory btree, all we do is tear down all the staged data and return
an errno to userspace. In-memory btrees need not be transactional, so
their buffers should not be committed to the ondisk log, nor should they
be checkpointed by the AIL. That's just as well since the ephemeral
nature of the btree means that the buftarg and the buffers may disappear
quickly anyway.
Therefore, we need a way to launder the btree buffers that get attached
to the transaction by the generic btree code. Because the buffers are
directly mapped to backing file pages, there's no need to bwrite them
back to the tmpfs file. All we need to do is clean enough of the buffer
log item state so that the bli can be detached from the buffer, remove
the bli from the transaction's log item list, and reset the transaction
dirty state as if the laundered items had never been there.
For simplicity, create xfbtree transaction commit and cancel helpers
that launder the in-memory btree buffers for callers. Once laundered,
call the write verifier on non-stale buffers to avoid integrity issues,
or punch a hole in the backing file for stale buffers.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:35 +0000 (12:43 -0800)]
xfs: support in-memory btrees
Adapt the generic btree cursor code to be able to create a btree whose
buffers come from a (presumably in-memory) buftarg with a header block
that's specific to in-memory btrees. We'll connect this to other parts
of online scrub in the next patches.
Note that in-memory btrees always have a block size matching the system
memory page size for efficiency reasons. There are also a few things we
need to do to finalize a btree update; that's covered in the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:43:21 +0000 (12:43 -0800)]
xfs: support in-memory buffer cache targets
Allow the buffer cache to target in-memory files by making it possible
to have a buftarg that maps pages from private shmem files. As the
prevous patch alludes, the in-memory buftarg contains its own cache,
points to a shmem file, and does not point to a block_device.
The next few patches will make it possible to construct an xfs_btree in
pageable memory by using this buftarg.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:42:58 +0000 (12:42 -0800)]
xfs: teach buftargs to maintain their own buffer hashtable
Currently, cached buffers are indexed by per-AG hashtables. This works
great for the data device, but won't work for in-memory btrees. To
handle that use case, buftargs will need to be able to index buffers
independently of other data structures.
We accomplish this by hoisting the rhashtable and its lock into a
separate xfs_buf_cache structure, make the buftarg point to the
_buf_cache structure, and rework various functions to use it. This
will enable the in-memory buftarg to come up with its own _buf_cache.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
xfs: move setting bt_logical_sectorsize out of xfs_setsize_buftarg
bt_logical_sectorsize and the associated mask is set based on the
constant logical block size in the block_device structure and thus
doesn't need to be updated in xfs_setsize_buftarg. Move it into
xfs_alloc_buftarg so that it is only done once per buftarg.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs: split xfs_buf_rele for cached vs uncached buffers
xfs_buf_rele is a bit confusing because it mixes up handling of normal
cached and the special uncached buffers without much explanation.
Split the handling into two different helpers, and use a clearly named
helper that checks the hash key to distinguish the two cases instead
of checking the pag pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Despite its name, xfs_btree_read_bufl doesn't contain any btree-related
functionaliy and isn't used by the btree code. Move it to xfs_bmap.c,
hard code the refval and ops arguments and rename it to
xfs_bmap_read_buf.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs_btree_reada_bufl just wraps xfs_btree_readahead and a agblock
to daddr conversion. Just open code it's three callsites in the
two callers (One of which isn't even btree related).
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs: rename btree helpers that depends on the block number representation
All these helpers hardcode fsblocks or agblocks and not just the pointer
size. Rename them so that the names are still fitting when we add the
long format in-memory blocks and adjust the checks when calling them to
check the btree types and not just pointer length.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Add a __xfs_btree_check_block helper that can be called by the scrub code
to validate a btree block of any form, and move the duplicate error
handling code from xfs_btree_check_sblock and xfs_btree_check_lblock into
xfs_btree_check_block and thus remove these two helpers.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Merge xfs_btree_check_sptr and xfs_btree_check_lptr into a single
__xfs_btree_check_ptr that can be shared between xfs_btree_check_ptr
and the scrub code.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Stop using xfs_btree_check_lptr in xfs_btree_check_lblock_siblings,
as it only duplicates the xfs_verify_fsbno call in the other leg of
if / else besides adding a tautological level check.
With this the cur and level arguments can be removed as they are
now unused.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Stop using xfs_btree_check_sptr in xfs_btree_check_sblock_siblings,
as it only duplicates the xfs_verify_agbno call in the other leg of
if / else besides adding a tautological level check.
With this the cur and level arguments can be removed as they are
now unused.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The last checks for bc_btnum can be replaced with helpers that check
the btree ops. This allows adding new btrees to XFS without having
to update a global enum.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: complete the ops predicates] Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Split xfs_inobt_init_cursor into separate routines for the inobt and
finobt to prepare for the removal of the xfs_btnum global enumeration
of btree types.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The which variable that holds a btree number is passed to two functions
that ignore it and used in a single check that can check the sm_type
as well. Remove it to unclutter the code.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Split xfs_allocbt_init_cursor into separate routines for the by-bno
and by-cnt btrees to prepare for the removal of the xfs_btnum global
enumeration of btree types.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The btnum in struct xfs_btree_ops is often used for printing a symbolic
name for the btree. Add a name field to the ops structure and use that
directly.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs: fold xfs_bmbt_init_common into xfs_bmbt_init_cursor
Make the levels initialization in xfs_bmbt_init_cursor conditional
and merge the two helpers.
This requires the fakeroot case to now pass a -1 whichfork directly
into xfs_bmbt_init_cursor, and some special casing for that, but
at least this scheme to deal with the fake btree root is handled and
documented in once place now.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: tidy up a multline ternary] Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Darrick J. Wong [Thu, 22 Feb 2024 20:39:43 +0000 (12:39 -0800)]
xfs: make staging file forks explicit
Don't open-code "-1" for whichfork when we're creating a staging btree
for a repair; let's define an actual symbol to make grepping and
understanding easier.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
xfs: make full use of xfs_btree_stage_ifakeroot in xfs_bmbt_stage_cursor
Remove the duplicate cur->bc_nlevels assignment in xfs_bmbt_stage_cursor,
and move the cur->bc_ino.forksize assignment into
xfs_btree_stage_ifakeroot as it is part of setting up the fake btree
root.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Inode-rooted btrees don't need to initialize the root pointer in the
->init_ptr_from_cur method as the root is found by the
xfs_btree_get_iroot method later. Make ->init_ptr_from_cur option
for inode rooted btrees by providing a helper that does the right
thing for the given btree type and also documents the semantics.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Darrick J. Wong [Thu, 22 Feb 2024 20:37:24 +0000 (12:37 -0800)]
xfs: create predicate to determine if cursor is at inode root level
Create a predicate to decide if the given cursor and level point to the
root block in the inode immediate area instead of a disk block, and get
rid of the open-coded logic everywhere.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
xfs: split the per-btree union in struct xfs_btree_cur
Split up the union that encodes btree-specific fields in struct
xfs_btree_cur. Most fields in there are specific to the btree type
encoded in xfs_btree_ops.type, and we can use the obviously named union
for that. But one field is specific to the bmapbt and two are shared by
the refcount and rtrefcountbt. Move those to a separate union to make
the usage clear and not need a separate struct for the refcount-related
fields.
This will also make unnecessary some very awkward btree cursor
refc/rtrefc switching logic in the rtrefcount patchset.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs: split out a btree type from the btree ops geometry flags
Two of the btree cursor flags are always used together and encode
the fundamental btree type. There currently are two such types:
1) an on-disk AG-rooted btree with 32-bit pointers
2) an on-disk inode-rooted btree with 64-bit pointers
and we're about to add:
3) an in-memory btree with 64-bit pointers
Introduce a new enum and a new type field in struct xfs_btree_geom
to encode this type directly instead of using flags and change most
code to switch on this enum.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: make the pointer lengths explicit] Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Darrick J. Wong [Thu, 22 Feb 2024 20:35:36 +0000 (12:35 -0800)]
xfs: store the btree pointer length in struct xfs_btree_ops
Make the pointer length an explicit field in the btree operations
structure so that the next patch (which introduces an explicit btree
type enum) doesn't have to play a bunch of awkward games with inferring
the pointer length from the enumeration.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:35:22 +0000 (12:35 -0800)]
xfs: factor out a xfs_btree_owner helper
Split out a helper to calculate the owner for a given btree instead of
duplicating the logic in two places. While we're at it, make the
bc_ag/bc_ino switch logic depend on the correct geometry flag.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: break this up into two patches for the owner check] Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Darrick J. Wong [Thu, 22 Feb 2024 20:35:20 +0000 (12:35 -0800)]
xfs: move lru refs to the btree ops structure
Move the btree buffer LRU refcount to the btree ops structure so that we
can eliminate the last bc_btnum switch in the generic btree code. We're
about to create repair-specific btree types, and we don't want that
stuff cluttering up libxfs.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:35:17 +0000 (12:35 -0800)]
xfs: rename btree block/buffer init functions
Rename xfs_btree_init_block_int to xfs_btree_init_block, and
xfs_btree_init_block to xfs_btree_init_buf so that the name suggests the
type that caller are supposed to pass in.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:35:16 +0000 (12:35 -0800)]
xfs: initialize btree blocks using btree_ops structure
Notice now that the btree ops structure encodes btree geometry flags and
the magic number through the buffer ops. Refactor the btree block
initialization functions to use the btree ops so that we no longer have
to open code all that.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:34:29 +0000 (12:34 -0800)]
xfs: encode the btree geometry flags in the btree ops structure
Certain btree flags never change for the life of a btree cursor because
they describe the geometry of the btree itself. Encode these in the
btree ops structure and reduce the amount of code required in each btree
type's init_cursor functions. This also frees up most of the bits in
bc_flags.
A previous version of this patch also converted the open-coded flags
logic to helpers. This was removed due to the pending refactoring (that
follows this patch) to eliminate most of the state flags.
Darrick J. Wong [Thu, 22 Feb 2024 20:34:13 +0000 (12:34 -0800)]
xfs: fix imprecise logic in xchk_btree_check_block_owner
A reviewer was confused by the init_sa logic in this function. Upon
checking the logic, I discovered that the code is imprecise. What we
want to do here is check that there is an ownership record in the rmap
btree for the AG that contains a btree block.
For an inode-rooted btree (e.g. the bmbt) the per-AG btree cursors have
not been initialized because inode btrees can span multiple AGs.
Therefore, we must initialize the per-AG btree cursors in sc->sa before
proceeding. That is what init_sa controls, and hence the logic should
be gated on XFS_BTREE_ROOT_IN_INODE, not XFS_BTREE_LONG_PTRS.
In practice, ROOT_IN_INODE and LONG_PTRS are coincident so this hasn't
mattered. However, we're about to refactor both of those flags into
separate btree_ops fields so we want this the logic to make sense
afterwards.
Fixes: 858333dcf021a ("xfs: check btree block ownership with bnobt/rmapbt when scrubbing btree") Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:34:12 +0000 (12:34 -0800)]
xfs: drop XFS_BTREE_CRC_BLOCKS
All existing btree types set XFS_BTREE_CRC_BLOCKS when running against a
V5 filesystem. All currently proposed btree types are V5 only and use
the richer XFS_BTREE_CRC_BLOCKS format. Therefore, we can drop this
flag and change the conditional to xfs_has_crc.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:33:05 +0000 (12:33 -0800)]
xfs: repair summary counters
Use the same summary counter calculation infrastructure to generate new
values for the in-core summary counters. The difference between the
scrubber and the repairer is that the repairer will freeze the fs during
setup, which means that the values should match exactly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:33:04 +0000 (12:33 -0800)]
xfs: update health status if we get a clean bill of health
If scrub finds that everything is ok with the filesystem, we need a way
to tell the health tracking that it can let go of indirect health flags,
since indirect flags only mean that at some point in the past we lost
some context.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:33:03 +0000 (12:33 -0800)]
xfs: add secondary and indirect classes to the health tracking system
Establish two more classes of health tracking bits:
* Indirect problems, which suggest problems in other health domains
that we weren't able to preserve.
* Secondary problems, which track state that's related to primary
evidence of health problems; and
The first class we'll use in an upcoming patch to record in the AG
health status the fact that we ran out of memory and had to inactivate
an inode with defective metadata. The second class we use to indicate
that repair knows that an inode is bad and we need to fix it later.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:31:03 +0000 (12:31 -0800)]
xfs: report ag header corruption errors to the health tracking system
Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:
Darrick J. Wong [Thu, 22 Feb 2024 20:31:02 +0000 (12:31 -0800)]
xfs: report fs corruption errors to the health tracking system
Whenever we encounter corrupt fs metadata, we should report that to the
health monitoring system for later reporting. A convenient program for
identifying places to insert xfs_*_mark_sick calls is as follows:
Darrick J. Wong [Thu, 22 Feb 2024 20:31:01 +0000 (12:31 -0800)]
xfs: separate the marking of sick and checked metadata
Split the setting of the sick and checked masks into separate functions
as part of preparing to add the ability for regular runtime fs code
(i.e. not scrub) to mark metadata structures sick when corruptions are
found. Improve the documentation of libxfs' requirements for helper
behavior.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:30:59 +0000 (12:30 -0800)]
xfs: track directory entry updates during live nlinks fsck
Create the necessary hooks in the directory operations
(create/link/unlink/rename) code so that our live nlink scrub code can
stay up to date with link count updates in the rest of the filesystem.
This will be the means to keep our shadow link count information up to
date while the scan runs in real time.
In online fsck part 2, we'll use these same hooks to handle repairs
to directories and parent pointer information.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:30:58 +0000 (12:30 -0800)]
xfs: teach scrub to check file nlinks
Create the necessary scrub code to walk the filesystem's directory tree
so that we can compute file link counts. Similar to quotacheck, we
create an incore shadow array of link count information and then we walk
the filesystem a second time to compare the link counts. We need live
updates to keep the information up to date during the lengthy scan, so
this scrubber remains disabled until the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong [Thu, 22 Feb 2024 20:30:56 +0000 (12:30 -0800)]
xfs: repair cannot update the summary counters when logging quota flags
While running xfs/804 (quota repairs racing with fsstress), I observed a
filesystem shutdown in the primary sb write verifier:
run fstests xfs/804 at 2022-05-23 18:43:48
XFS (sda4): Mounting V5 Filesystem
XFS (sda4): Ending clean mount
XFS (sda4): Quotacheck needed: Please wait.
XFS (sda4): Quotacheck: Done.
XFS (sda4): EXPERIMENTAL online scrub feature in use. Use at your own risk!
XFS (sda4): SB ifree sanity check failed 0xb5 > 0x80
XFS (sda4): Metadata corruption detected at xfs_sb_write_verify+0x5e/0x100 [xfs], xfs_sb block 0x0
XFS (sda4): Unmount and run xfs_repair
The "SB ifree sanity check failed" message was a debugging printk that I
added to the kernel; observe that 0xb5 - 0x80 = 53, which is less than
one inode chunk.
I traced this to the xfs_log_sb calls from the online quota repair code,
which tries to clear the CHKD flags from the superblock to force a
mount-time quotacheck if the repair fails. On a V5 filesystem,
xfs_log_sb updates the ondisk sb summary counters with the current
contents of the percpu counters. This is done without quiescing other
writer threads, which means it could be racing with a thread that has
updated icount and is about to update ifree.
If the other write thread had incremented ifree before updating icount,
the repair thread will write icount > ifree into the logged update. If
the AIL writes the logged superblock back to disk before anyone else
fixes this siutation, this will lead to a write verifier failure, which
causes a filesystem shutdown.
Resolve this problem by updating the quota flags and calling
xfs_sb_to_disk directly, which does not touch the percpu counters.
While we're at it, we can elide the entire update if the selected qflags
aren't set.
Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
projects / thirdparty / kernel / linux.git / log
