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Add three trace points for the different backing memory allocators for
buffers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Implement buffered writes including page faults and block zeroing for
zoned RT devices. Buffered writes to zoned RT devices are split into
three phases:
1) a reservation for the worst case data block usage is taken before
acquiring the iolock. When there are enough free blocks but not
enough available one, garbage collection is kicked off to free the
space before continuing with the write. If there isn't enough
freeable space, the block reservation is reduced and a short write
will happen as expected by normal Linux write semantics.
2) with the iolock held, the generic iomap buffered write code is
called, which through the iomap_begin operation usually just inserts
delalloc extents for the range in a single iteration. Only for
overwrites of existing data that are not block aligned, or zeroing
operations the existing extent mapping is read to fill out the srcmap
and to figure out if zeroing is required.
3) the ->map_blocks callback to the generic iomap writeback code
calls into the zoned space allocator to actually allocate on-disk
space for the range before kicking of the writeback.
Note that because all writes are out of place, truncate or hole punches
that are not aligned to block size boundaries need to allocate space.
For block zeroing from truncate, ->setattr is called with the iolock
(aka i_rwsem) already held, so a hacky deviation from the above
scheme is needed. In this case the space reservations is called with
the iolock held, but is required not to block and can dip into the
reserved block pool. This can lead to -ENOSPC when truncating a
file, which is unfortunate. But fixing the calling conventions in
the VFS is probably much easier with code requiring it already in
mainline.
Similarly because all writes are out place, the zoned allocator can't
support unwritten extents and thus the FALLOC_FL_ALLOCATE_RANGE range
mode of fallocate. Other fallocate modes that would reserved space
but don't need to to provide proper semantics do work but do not
reserve space.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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RT groups on a zoned file system need to be completely empty before their
space can be reused. This means that partially empty groups need to be
emptied entirely to free up space if no entirely free groups are
available.
Add a garbage collection thread that moves all data out of the least used
zone when not enough free zones are available, and which resets all zones
that have been emptied. To find empty zone a simple set of 10 buckets
based on the amount of space used in the zone is used. To empty zones,
the rmap is walked to find the owners and the data is read and then
written to the new place.
To automatically defragment files the rmap records are sorted by inode
and logical offset. This means defragmentation of parallel writes into
a single zone happens automatically when performing garbage collection.
Because holding the iolock over the entire GC cycle would inject very
noticeable latency for other accesses to the inodes, the iolock is not
taken while performing I/O. Instead the I/O completion handler checks
that the mapping hasn't changed over the one recorded at the start of
the GC cycle and doesn't update the mapping if it change.
Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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For zoned file systems garbage collection (GC) has to take the iolock
and mmaplock after moving data to a new place to synchronize with
readers. This means waiting for garbage collection with the iolock can
deadlock.
To avoid this, the worst case required blocks have to be reserved before
taking the iolock, which is done using a new RTAVAILABLE counter that
tracks blocks that are free to write into and don't require garbage
collection. The new helpers try to take these available blocks, and
if there aren't enough available it wakes and waits for GC. This is
done using a list of on-stack reservations to ensure fairness.
Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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For zoned RT devices space is always allocated at the write pointer, that
is right after the last written block and only recorded on I/O completion.
Because the actual allocation algorithm is very simple and just involves
picking a good zone - preferably the one used for the last write to the
inode. As the number of zones that can written at the same time is
usually limited by the hardware, selecting a zone is done as late as
possible from the iomap dio and buffered writeback bio submissions
helpers just before submitting the bio.
Given that the writers already took a reservation before acquiring the
iolock, space will always be readily available if an open zone slot is
available. A new structure is used to track these open zones, and
pointed to by the xfs_rtgroup. Because zoned file systems don't have
a rsum cache the space for that pointer can be reused.
Allocations are only recorded at I/O completion time. The scheme used
for that is very similar to the reflink COW end I/O path.
Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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Currently each metabtree inode has it's own space reservation to ensure
it can be expanded to the maximum size, mirroring what is done for the
AG-based btrees. But unlike the AG-based btrees the metabtree inodes
aren't restricted to allocate from a single AG but can use free space
form the entire file system. And unlike AG-based btrees where the
required reservation shrinks with the available free space due to this,
the metabtree reservations for the rtrmap and rtfreflink trees are not
bound in any way by the data device free space as they track RT extent
allocations. This is not very efficient as it requires a large number
of blocks to be set aside that can't be used at all by other btrees.
Switch to a model that uses a global pool instead in preparation for
reducing the amount of reserved space, which now also removes the
overloading of the i_nblocks field for metabtree inodes, which would
create problems if metabtree inodes ever had a big enough xattr fork
to require xattr blocks outside the inode.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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Add two tracepoints when the freecounter dips into the reserved pool
and when it is entirely out of space.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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xfs_{add,dec}_freecounter already handles the block and RT extent
percpu counters, but it currently hardcodes the passed in counter.
Add a freecounter abstraction that uses an enum to designate the counter
and add wrappers that hide the actual percpu_counters. This will allow
expanding the reserved block handling to the RT extent counter in the
next step, and also prepares for adding yet another such counter that
can share the code. Both these additions will be needed for the zoned
allocator.
Also switch the flooring of the frextents counter to 0 in statfs for the
rthinherit case to a manual min_t call to match the handling of the
fdblocks counter for normal file systems.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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xfs_buf_readahead_map is the only caller of xfs_buf_read_map and thus
_xfs_buf_read that is not synchronous. Split it from xfs_buf_read_map
so that the asynchronous path is self-contained and the now purely
synchronous xfs_buf_read_map / _xfs_buf_read implementation can be
simplified.
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: Carlos Maiolino <cem@kernel.org>
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Since commit 298f34224506 ("xfs: lockless buffer lookup") the buffer
lookup fastpath is done without a hash-wide lock (then pag_buf_lock, now
bc_lock) and only under RCU protection. But this means that nothing
serializes lookups against the temporary 0 reference count for buffers
that are added to the LRU after dropping the last regular reference,
and a concurrent lookup would fail to find them.
Fix this by doing all b_hold modifications under b_lock. We're already
doing this for release so this "only" ~ doubles the b_lock round trips.
We'll later look into the lockref infrastructure to optimize the number
of lock round trips again.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Rework the refcount btree cursor tracepoints in preparation to handle the
realtime refcount btree cursor. Mostly this involves renaming the field to
"refcbno" and extracting the group number from the cursor when possible.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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The size of filesystem transaction reservations depends on the maximum
height (maxlevels) of the realtime btrees. Since we don't want a grow
operation to increase the reservation size enough that we'll fail the
minimum log size checks on the next mount, constrain growfs operations
if they would cause an increase in those maxlevels.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a new fork format type for metadata btrees. This fork type
requires that the inode is in the metadata directory tree, and only
applies to the data fork. The actual type of the metadata btree itself
is determined by the di_metatype field.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Rework the rmap btree cursor tracepoints in preparation to handle the
realtime rmap btree cursor. Mostly this involves renaming the field to
"gbno" and extracting the group number from the cursor.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a new space reservation scheme so that btree metadata for the
realtime volume can reserve space in the data device to avoid space
underruns.
Back when we were testing the rmap and refcount btrees for the data
device, people observed occasional shutdowns when xfs_btree_split was
called for either of those two btrees. This happened when certain
operations (mostly writeback ioends) created new rmap or refcount
records, which would expand the size of the btree. If there were no
free blocks available the allocation would fail and the split would shut
down the filesystem.
I considered pre-reserving blocks for btree expansion at the time of a
write() call, but there wasn't any good way to attach the reservations
to an inode and keep them there all the way to ioend processing. Unlike
delalloc reservations which have that indlen mechanism, there's no way
to do that for mapped extents; and indlen blocks are given back during
the delalloc -> unwritten transition.
The solution was to reserve sufficient blocks for rmap/refcount btree
expansion at mount time. This is what the XFS_AG_RESV_* flags provide;
any expansion of those two btrees can come from the pre-reserved space.
This patch brings that pre-reservation ability to inode-rooted btrees so
that the rt rmap and refcount btrees can also save room for future
expansion.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge
xfs: shard the realtime section [v5.5 06/10]
Right now, the realtime section uses a single pair of metadata inodes to
store the free space information. This presents a scalability problem
since every thread trying to allocate or free rt extents have to lock
these files. Solve this problem by sharding the realtime section into
separate realtime allocation groups.
While we're at it, define a superblock to be stamped into the start of
the rt section. This enables utilities such as blkid to identify block
devices containing realtime sections, and avoids the situation where
anything written into block 0 of the realtime extent can be
misinterpreted as file data.
The best advantage for rtgroups will become evident later when we get to
adding rmap and reflink to the realtime volume, since the geometry
constraints are the same for rt groups and AGs. Hence we can reuse all
that code directly.
This is a very large patchset, but it catches us up with 20 years of
technical debt that have accumulated.
With a bit of luck, this should all go splendidly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge
xfs: create incore rt allocation groups [v5.5 04/10]
Add in-memory data structures for sharding the realtime volume into
independent allocation groups. For existing filesystems, the entire rt
volume is modelled as having a single large group, with (potentially) a
number of rt extents exceeding 2^32 blocks, though these are not likely
to exist because the codebase has been a bit broken for decades. The
next series fills in the ondisk format and other supporting structures.
With a bit of luck, this should all go splendidly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge
xfs: metadata inode directory trees [v5.5 03/10]
This series delivers a new feature -- metadata inode directories. This
is a separate directory tree (rooted in the superblock) that contains
only inodes that contain filesystem metadata. Different metadata
objects can be looked up with regular paths.
Start by creating xfs_imeta{dir,file}* functions to mediate access to
the metadata directory tree. By the end of this mega series, all
existing metadata inodes (rt+quota) will use this directory tree instead
of the superblock.
Next, define the metadir on-disk format, which consists of marking
inodes with a new iflag that says they're metadata. This prevents
bulkstat and friends from ever getting their hands on fs metadata files.
With a bit of luck, this should all go splendidly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge
xfs: create a generic allocation group structure [v5.5 02/10]
Soon we'll be sharding the realtime volume into separate allocation
groups. These rt groups will /mostly/ behave the same as the ones on
the data device, but since rt groups don't have quite the same set of
struct fields as perags, let's hoist the parts that will be shared by
both into a common xfs_group object.
With a bit of luck, this should all go splendidly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge
xfs: convert perag to use xarrays [v5.5 01/10]
Convert the xfs_mount perag tree to use an xarray instead of a radix
tree. There should be no functional changes here.
With a bit of luck, this should all go splendidly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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For rtgroups filesystems, track newly freed (rt) space through the log
until the rt EFIs have been committed to disk. This way we ensure that
space cannot be reused until all traces of the old owner are gone.
As a fringe benefit, we now support -o discard on the realtime device.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Port xfs_discard_extents and its tracepoints to handle generic groups
instead of just perags. This is needed to enable busy extent tracking
for rtgroups.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Teach the EFI mechanism how to free realtime extents. We're going to
need this to enforce proper ordering of operations when we enable
realtime rmap.
Declare a new log intent item type (XFS_LI_EFI_RT) and a separate defer
ops for rt extents. This keeps the ondisk artifacts and processing code
completely separate between the rt and non-rt cases. Hopefully this
will make it easier to debug filesystem problems.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Make the bmap intent items take an active reference to the rtgroup
containing the space that is being mapped or unmapped. We will need
this functionality once we start enabling rmap and reflink on the rt
volume. Technically speaking we need it even for !rtgroups filesystems
to prevent the (dummy) rtgroup 0 from going away, even though this will
never happen.
As a bonus, we can rework the xfs_bmap_deferred_class tracepoint to use
the xfs_group object to figure out the type and group number, widen the
group block number field to fit 64-bit quantities, and get rid of the
now redundant opdev and rtblock fields.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Record the state of per-rtgroup metadata sickness in the rtgroup
structure for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create an incore object that will contain information about a realtime
allocation group. This will eventually enable us to shard the realtime
section in a similar manner to how we shard the data section, but for
now just a single object for the entire RT subvolume is created.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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The calling conventions for xfs_getfsmap_helper are confusing -- callers
pass in an rmap record, but they must also supply startblock and
blockcount in daddr units. This was bolted onto the original fsmap
implementation so that we could report *something* for realtime
volumes, which do not support rmap and hence can draw only from the rt
free space bitmap. Free space on the rt volume can be more than 2^32
fsblocks long, which means that we can't use the rmap startblock or
blockcount fields.
This is confusing for callers, because they must supplying redundant
data, but not all of it is used. Streamline this by creating a separate
fsmap irec structure that contains exactly the data we need, once.
Note that we actually do need rm_startblock for rmap key comparisons
when we're actually querying an rmap btree, so leave that field but
document why it's there.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Plumb in the bits we need to load metadata inodes from a named entry in
a metadir directory, create (or hardlink) inodes into a metadir
directory, create metadir directories, and flag inodes as being metadata
files.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Replace the pag pointers in the type specific union with a generic
xfs_group pointer. This prepares for adding realtime group support.
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>
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Prepare for tracking busy RT extents by passing the generic group
structure to the xfs_extent_busy_class tracepoints.
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>
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Prepare supporting the upcoming realtime groups feature by moving the
deferred operation draining to the generic xfs_group structure.
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>
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Prepare for also tracking the health status of the upcoming realtime
groups by moving the health tracking code to the generic xfs_group
structure.
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>
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Split the lookup and refcount handling of struct xfs_perag into an
embedded xfs_group structure that can be reused for the upcoming
realtime groups.
It will be extended with more features later.
Note that he xg_type field will only need a single bit even with
realtime group support. For now it fills a hole, but it might be
worth to fold it into another field if we can use this space better.
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>
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Convert all tracepoints that take [mp,agno] tuples to take a pag argument
instead so that decoding only happens when tracepoints are enabled and to
clean up the callers.
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>
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So that decoding is only done when tracing is actually enabled and the
call site look a lot neater.
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>
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Pass the perag structure and the irec to these tracepoints so that the
decoding is only done when tracing is actually enabled and the call sites
look a lot neater.
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>
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And remove the single instance class indirection for it.
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>
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Trace points never modify their arguments. Mark all the pag objects
passed to trace points. The exception is the xfs_ag_resv_class, which
uses the xfs_perag_resv helper that can't be marked const due to
other users modifying the returned structure.
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>
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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>
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xfs_free_ag_extent already has a pointer to the pag structure through
the agf buffer. Use that instead of passing the redundant argument,
and do the same for the tracepoint.
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>
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Split the xfs_filemap_fault trace event into separate ones for read and
write faults and move them into the applicable locations.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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When the main loop in xfs_filestream_pick_ag fails to find a suitable
AG it tries to just pick the online AG. But the loop for that uses
args->pag as loop iterator while the later code expects pag to be
set. Fix this by reusing the max_pag case for this last resort, and
also add a check for impossible case of no AG just to make sure that
the uninitialized pag doesn't even escape in theory.
Reported-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Fixes: f8f1ed1ab3baba ("xfs: return a referenced perag from filestreams allocator")
Cc: <stable@vger.kernel.org> # v6.3
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_reclaim_inodes_count iterates over all AGs to sum up the reclaimable
inodes counts. There is no point in grabbing a reference to the them or
unlock the RCU critical section for each iteration, so switch to the
more efficient xas_for_each_marked iterator.
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>
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Pass the old perag structure to the tagged loop helpers so that they can
grab the old agno before releasing the reference. This removes the need
to separately track the agno and the iterator macro, and thus also
obsoletes the for_each_perag_tag syntactic sugar.
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>
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This patch introduces two more new ioctls to manage atomic updates to
file contents -- XFS_IOC_START_COMMIT and XFS_IOC_COMMIT_RANGE. The
commit mechanism here is exactly the same as what XFS_IOC_EXCHANGE_RANGE
does, but with the additional requirement that file2 cannot have changed
since some sampling point. The start-commit ioctl performs the sampling
of file attributes.
Note: This patch currently samples i_ctime during START_COMMIT and
checks that it hasn't changed during COMMIT_RANGE. This isn't entirely
safe in kernels prior to 6.12 because ctime only had coarse grained
granularity and very fast updates could collide with a COMMIT_RANGE.
With the multi-granularity ctime introduced by Jeff Layton, it's now
possible to update ctime such that this does not happen.
It is critical, then, that this patch must not be backported to any
kernel that does not support fine-grained file change timestamps.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Since file_path() takes the output buffer as one of its arguments, we
might as well have it format directly into the tracepoint's char array
instead of wasting stack space.
Fixes: 3934e8ebb7cc6 ("xfs: create a big array data structure")
Fixes: 5076a6040ca16 ("xfs: support in-memory buffer cache targets")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403290419.HPcyvqZu-lkp@intel.com/
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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The grant heads in the log track the space reserved in the log for
running transactions. They do this by tracking how far ahead of the
tail that the reservation has reached, and the units for doing this
are {cycle,bytes} for the reserve head rather than {cycle,blocks}
which are normal used by LSNs.
This is annoyingly complex because we have to split, crack and
combined these tuples for any calculation we do to determine log
space and targets. This is computationally expensive as well as
difficult to do atomically and locklessly, as well as limiting the
size of the log to 2^32 bytes.
Really, though, all the grant heads are tracking is how much space
is currently available for use in the log. We can track this as a
simply byte count - we just don't care what the actual physical
location in the log the head and tail are at, just how much space we
have remaining before the head and tail overlap.
So, convert the grant heads to track the byte reservations that are
active rather than the current (cycle, offset) tuples. This means an
empty log has zero bytes consumed, and a full log is when the
reservations reach the size of the log minus the space consumed by
the AIL.
This greatly simplifies the accounting and checks for whether there
is space available. We no longer need to crack or combine LSNs to
determine how much space the log has left, nor do we need to look at
the head or tail of the log to determine how close to full we are.
There is, however, a complexity that needs to be handled. We know
how much space is being tracked in the AIL now via log->l_tail_space
and the log tickets track active reservations and return the unused
portions to the grant heads when ungranted. Unfortunately, we don't
track the used portion of the grant, so when we transfer log items
from the CIL to the AIL, the space accounted to the grant heads is
transferred to the log tail space. Hence when we move the AIL head
forwards on item insert, we have to remove that space from the grant
heads.
We also remove the xlog_verify_grant_tail() debug function as it is
no longer useful. The check it performs has been racy since delayed
logging was introduced, but now it is clearly only detecting false
positives so remove it.
The result of this substantially simpler accounting algorithm is an
increase in sustained transaction rate from ~1.3 million
transactions/s to ~1.9 million transactions/s with no increase in
CPU usage. We also remove the 32 bit space limitation on the grant
heads, which will allow us to increase the journal size beyond 2GB
in future.
Note that this renames the sysfs files exposing the log grant space
now that the values are exported in bytes. This allows xfstests
to auto-detect the old or new ABI.
[hch: move xlog_grant_sub_space out of line,
update the xlog_grant_{add,sub}_space prototypes,
rename the sysfs files to allow auto-detection in xfstests]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-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>
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The current implementation of xlog_assign_tail_lsn() assumes that
when the AIL is empty, the log tail matches the LSN of the last
written commit record. This is recorded in xlog_state_set_callback()
as log->l_last_sync_lsn when the iclog state changes to
XLOG_STATE_CALLBACK. This change is then immediately followed by
running the callbacks on the iclog which then insert the log items
into the AIL at the "commit lsn" of that checkpoint.
The AIL tracks log items via the start record LSN of the checkpoint,
not the commit record LSN. This is because we can pipeline multiple
checkpoints, and so the start record of checkpoint N+1 can be
written before the commit record of checkpoint N. i.e:
start N commit N
+-------------+------------+----------------+
start N+1 commit N+1
The tail of the log cannot be moved to the LSN of commit N when all
the items of that checkpoint are written back, because then the
start record for N+1 is no longer in the active portion of the log
and recovery will fail/corrupt the filesystem.
Hence when all the log items in checkpoint N are written back, the
tail of the log most now only move as far forwards as the start LSN
of checkpoint N+1.
Hence we cannot use the maximum start record LSN the AIL sees as a
replacement the pointer to the current head of the on-disk log
records. However, we currently only use the l_last_sync_lsn when the
AIL is empty - when there is no start LSN remaining, the tail of the
log moves to the LSN of the last commit record as this is where
recovery needs to start searching for recoverable records. THe next
checkpoint will have a start record LSN that is higher than
l_last_sync_lsn, and so everything still works correctly when new
checkpoints are written to an otherwise empty log.
l_last_sync_lsn is an atomic variable because it is currently
updated when an iclog with callbacks attached moves to the CALLBACK
state. While we hold the icloglock at this point, we don't hold the
AIL lock. When we assign the log tail, we hold the AIL lock, not the
icloglock because we have to look up the AIL. Hence it is an atomic
variable so it's not bound to a specific lock context.
However, the iclog callbacks are only used for CIL checkpoints. We
don't use callbacks with unmount record writes, so the
l_last_sync_lsn variable only gets updated when we are processing
CIL checkpoint callbacks. And those callbacks run under AIL lock
contexts, not icloglock context. The CIL checkpoint already knows
what the LSN of the iclog the commit record was written to (obtained
when written into the iclog before submission) and so we can update
the l_last_sync_lsn under the AIL lock in this callback. No other
iclog callbacks will run until the currently executing one
completes, and hence we can update the l_last_sync_lsn under the AIL
lock safely.
This means l_last_sync_lsn can move to the AIL as the "ail_head_lsn"
and it can be used to replace the atomic l_last_sync_lsn in the
iclog code. This makes tracking the log tail belong entirely to the
AIL, rather than being smeared across log, iclog and AIL state and
locking.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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Pass the incore refcount intent structure to the tracepoints instead of
open-coding the argument passing.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Prepare the rest of refcount btree tracepoints for use with realtime
reflink by making them take the btree cursor object as a parameter.
This will save us a lot of trouble later on.
Remove the xfs_refcount_recover_extent tracepoint since it's already
covered by other refcount tracepoints.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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