12 Jan, 2017
7 commits
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commit 0260d8ff5f76617e3a55a1c471383ecb4404c3ad upstream.
COW fork reservation is implemented via delayed allocation. The code is
modeled after the traditional delalloc allocation code, but is slightly
different in terms of how preallocation occurs. Rather than post-eof
speculative preallocation, COW fork preallocation is implemented via a
COW extent size hint that is designed to minimize fragmentation as a
reflinked file is split over time.xfs_reflink_reserve_cow() still uses logic that is oriented towards
dealing with post-eof speculative preallocation, however, and is stale
or not necessarily correct. First, the EOF alignment to the COW extent
size hint is implemented in xfs_bmapi_reserve_delalloc() (which does so
correctly by aligning the start and end offsets) and so is not necessary
in xfs_reflink_reserve_cow(). The backoff and retry logic on ENOSPC is
also ineffective for the same reason, as xfs_bmapi_reserve_delalloc()
will simply perform the same allocation request on the retry. Finally,
since the COW extent size hint aligns the start and end offset of the
range to allocate, the end_fsb != orig_end_fsb logic is not sufficient.
Indeed, if a write request happens to end on an aligned offset, it is
possible that we do not tag the inode for COW preallocation even though
xfs_bmapi_reserve_delalloc() may have preallocated at the start offset.Kill the unnecessary, duplicate code in xfs_reflink_reserve_cow().
Remove the inode tag logic as well since xfs_bmapi_reserve_delalloc()
has been updated to tag the inode correctly.Signed-off-by: Brian Foster
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit 2755fc4438501c8c28e7783df890e889f6772bee upstream.
Signed-off-by: Christoph Hellwig
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit 974ae922efd93b07b6cdf989ae959883f6f05fd8 upstream.
Speculative preallocation is currently processed entirely by the callers
of xfs_bmapi_reserve_delalloc(). The caller determines how much
preallocation to include, adjusts the extent length and passes down the
resulting request.While this works fine for post-eof speculative preallocation, it is not
as reliable for COW fork preallocation. COW fork preallocation is
implemented via the cowextszhint, which aligns the start offset as well
as the length of the extent. Further, it is difficult for the caller to
accurately identify when preallocation occurs because the returned
extent could have been merged with neighboring extents in the fork.To simplify this situation and facilitate further COW fork preallocation
enhancements, update xfs_bmapi_reserve_delalloc() to take a separate
preallocation parameter to incorporate into the allocation request. The
preallocation blocks value is tacked onto the end of the request and
adjusted to accommodate neighboring extents and extent size limits.
Since xfs_bmapi_reserve_delalloc() now knows precisely how much
preallocation was included in the allocation, it can also tag the inodes
appropriately to support preallocation reclaim.Note that xfs_bmapi_reserve_delalloc() callers are not yet updated to
use the preallocation mechanism. This patch should not change behavior
outside of correctly tagging reflink inodes when start offset
preallocation occurs (which the caller does not handle correctly).Signed-off-by: Brian Foster
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit 65c5f419788d623a0410eca1866134f5e4628594 upstream.
We can easily lookup the previous extent for the cases where we need it,
which saves the callers from looking it up for us later in the series.Signed-off-by: Christoph Hellwig
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit fba3e594ef0ad911fa8f559732d588172f212d71 upstream.
It turns out that btrfs and xfs had differing interpretations of what
to do when the dedupe length is zero. Change xfs to follow btrfs'
semantics so that the userland interface is consistent.Signed-off-by: Darrick J. Wong
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit 5d829300bee000980a09ac2ccb761cb25867b67c upstream.
The open-coded pattern:
ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t)
is all over the xfs code; provide a new helper
xfs_iext_count(ifp) to count the number of inline extents
in an inode fork.[dchinner: pick up several missed conversions]
Signed-off-by: Eric Sandeen
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman -
commit 399372349a7f9b2d7e56e4fa4467c69822d07024 upstream.
The cowblocks background scanner currently clears the cowblocks tag
for inodes without any real allocations in the cow fork. This
excludes inodes with only delalloc blocks in the cow fork. While we
might never expect to clear delalloc blocks from the cow fork in the
background scanner, it is not necessarily correct to clear the
cowblocks tag from such inodes.For example, if the background scanner happens to process an inode
between a buffered write and writeback, the scanner catches the
inode in a state after delalloc blocks have been allocated to the
cow fork but before the delalloc blocks have been converted to real
blocks by writeback. The background scanner then incorrectly clears
the cowblocks tag, even if part of the aforementioned delalloc
reservation will not be remapped to the data fork (i.e., extra
blocks due to the cowextsize hint). This means that any such
additional blocks in the cow fork might never be reclaimed by the
background scanner and could persist until the inode itself is
reclaimed.To address this problem, only skip and clear inodes without any cow
fork allocations whatsoever from the background scanner. While we
generally do not want to cancel delalloc reservations from the
background scanner, the pagecache dirty check following the
cowblocks check should prevent that situation. If we do end up with
delalloc cow fork blocks without a dirty address space mapping, this
is probably an indication that something has gone wrong and the
blocks should be reclaimed, as they may never be converted to a real
allocation.Signed-off-by: Brian Foster
Reviewed-by: Darrick J. Wong
Signed-off-by: Dave Chinner
Cc: Christoph Hellwig
Signed-off-by: Greg Kroah-Hartman
24 Oct, 2016
1 commit
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The background cowblocks scan job takes care of scanning for inodes with
potentially lingering blocks in the cow fork and clearing them out. If
the background scanner reclaims the cow fork blocks, however, it doesn't
immediately clear the cowblocks tag from the inode. Instead, the inode
remains tagged until the background scanner comes around again,
discovers the inode cow fork has no blocks, clears the tag and fires the
trace_xfs_inode_free_cowblocks_invalid() tracepoint to indicate that the
inode may have been incorrectly tagged.This is not a major functional problem as the tag is ultimately cleared.
Nonetheless, clear the tag when an inode cow fork is explicitly emptied
to avoid the extra round trip through the background scanner and
spurious "invalid" tracepoint.Signed-off-by: Brian Foster
Reviewed-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Signed-off-by: Dave Chinner
20 Oct, 2016
8 commits
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Instead of doing a full extent list search for each extent that is
to be deleted using xfs_bmapi_read and then doing another one inside
of xfs_bunmapi_cow use the same scheme that xfs_bumapi uses: look
up the last extent to be deleted and then use the extent index to
walk downward until we are outside the range to be deleted.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner -
Rewrite xfs_reflink_cancel_cow_blocks so that we only do a search for
the first extent in the extent list and then iterate over the remaining
extents using the extent index, passing the extent we operate on
directly to xfs_bmap_del_extent_delay or xfs_bmap_del_extent_cow instead
of going through xfs_bunmapi and doing yet another extent list lookup.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner -
Split out two helpers for deleting delayed or real extents from the COW fork.
This allows to call them directly from xfs_reflink_cow_end_io once that
function is refactored to iterate the extent tree. It will also allow
to reuse the delalloc deletion from xfs_bunmapi in the future.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner -
Instead of reserving space as the first thing in write_begin move it past
reading the extent in the data fork. That way we only have to read from
the data fork once and can reuse that information for trimming the extent
to the shared/unshared boundary. Additionally this allows to easily
limit the actual write size to said boundary, and avoid a roundtrip on the
ilock.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner -
Delalloc extents in the extent list contain the number of reserved
indirect blocks in their startblock value and don't use the magic
DELAYSTARTBLOCK constant. Ensure that xfs_reflink_trim_around_shared
handles them properly by checking for isnullstartblock().Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Reviewed-by: Brian Foster
Signed-off-by: Dave Chinner -
There is no clear division of responsibility between those functions, so
just merge them into one to keep the code simple. Also move
xfs_file_wait_for_io to xfs_reflink.c together with its only caller.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Signed-off-by: Dave Chinner -
We need the iolock protection to stabilizie the IS_SWAPFILE and
IS_IMMUTABLE values, as well as preventing new buffered writers
re-dirtying the file data that we just wrote out.Signed-off-by: Christoph Hellwig
Reviewed-by: Darrick J. Wong
Signed-off-by: Dave Chinner -
with gcc 4.1.2:
fs/xfs/xfs_reflink.c: In function xfs_reflink_reserve_cow_range:
fs/xfs/xfs_reflink.c:327: warning: error may be used uninitialized in this functionIndeed, if "count" is zero, the function will return an uninitialized
error value.While "count" is unlikely to be zero, this function is called through
the public iomap API. Hence fix this by preinitializing error to zero.Fixes: 2a06705cd5954030 ("xfs: create delalloc extents in CoW fork")
Signed-off-by: Geert Uytterhoeven
Reviewed-by: Christoph Hellwig
Signed-off-by: Dave Chinner
10 Oct, 2016
4 commits
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Eric Sandeen reported a gcc complaint about uninitialized error
variables, so fix that.Signed-off-by: Darrick J. Wong
Reported-by: Eric Sandeen
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner -
Now that fallocate has an explicit unshare flag again, let's try
to remove the inode reflink flag whenever the user unshares any
part of a file since checking is cheap compared to the CoW.Signed-off-by: Darrick J. Wong
Reported-by: Brian Foster
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner -
The loop in _reflink_clear_inode_flag isn't necessary since we
jump out if any part of any extent is shared. Remove the loop
and we no longer need two maps, so we can save some stack use.Signed-off-by: Darrick J. Wong
Reported-by: Brian Foster
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner -
There are a couple of places where we don't check the inode's
reflink flag before calling into the reflink code. Fix those,
and add some asserts so we don't make this mistake again.Signed-off-by: Darrick J. Wong
Reported-by: Brian Foster
Reviewed-by: Dave Chinner
Signed-off-by: Dave Chinner
06 Oct, 2016
9 commits
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Trim CoW reservations made on behalf of a cowextsz hint if they get too
old or we run low on quota, so long as we don't have dirty data awaiting
writeback or directio operations in progress.Garbage collection of the cowextsize extents are kept separate from
prealloc extent reaping because setting the CoW prealloc lifetime to a
(much) higher value than the regular prealloc extent lifetime has been
useful for combatting CoW fragmentation on VM hosts where the VMs
experience bursty write behaviors and we can keep the utilization ratios
low enough that we don't start to run out of space. IOWs, it benefits
us to keep the CoW fork reservations around for as long as we can unless
we run out of blocks or hit inode reclaim.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
If the AG free space is down to the reserves, refuse to reflink our
way out of space. Hopefully userspace will make a real copy and/or go
elsewhere.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
Create a per-inode extent size allocator hint for copy-on-write. This
hint is separate from the existing extent size hint so that CoW can
take advantage of the fragmentation-reducing properties of extent size
hints without disabling delalloc for regular writes.The extent size hint that's fed to the allocator during a copy on
write operation is the greater of the cowextsize and regular extsize
hint.During reflink, if we're sharing the entire source file to the entire
destination file and the destination file doesn't already have a
cowextsize hint, propagate the source file's cowextsize hint to the
destination file.Furthermore, zero the bulkstat buffer prior to setting the fields
so that we don't copy kernel memory contents into userspace.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
Unshare all shared extents if the user calls fallocate with the new
unshare mode flag set, so that we can guarantee that a subsequent
write will not ENOSPC.Signed-off-by: Darrick J. Wong
[hch: pass inode instead of file to xfs_reflink_dirty_range,
use iomap infrastructure for copy up]
Signed-off-by: Christoph Hellwig -
Define a VFS function which allows userspace to request that the
kernel reflink a range of blocks between two files if the ranges'
contents match. The function fits the new VFS ioctl that standardizes
the checking for the btrfs EXTENT SAME ioctl.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
Reflink extents from one file to another; that is to say, iteratively
remove the mappings from the destination file, copy the mappings from
the source file to the destination file, and increment the reference
count of all the blocks that got remapped.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
Due to the way the CoW algorithm in XFS works, there's an interval
during which blocks allocated to handle a CoW can be lost -- if the FS
goes down after the blocks are allocated but before the block
remapping takes place. This is exacerbated by the cowextsz hint --
allocated reservations can sit around for a while, waiting to get
used.Since the refcount btree doesn't normally store records with refcount
of 1, we can use it to record these in-progress extents. In-progress
blocks cannot be shared because they're not user-visible, so there
shouldn't be any conflicts with other programs. This is a better
solution than holding EFIs during writeback because (a) EFIs can't be
relogged currently, (b) even if they could, EFIs are bound by
available log space, which puts an unnecessary upper bound on how much
CoW we can have in flight, and (c) we already have a mechanism to
track blocks.At mount time, read the refcount records and free anything we find
with a refcount of 1 because those were in-progress when the FS went
down.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig -
For O_DIRECT writes to shared blocks, we have to CoW them just like
we would with buffered writes. For writes that are not block-aligned,
just bounce them to the page cache.For block-aligned writes, however, we can do better than that. Use
the same mechanisms that we employ for buffered CoW to set up a
delalloc reservation, allocate all the blocks at once, issue the
writes against the new blocks and use the same ioend functions to
remap the blocks after the write. This should be fairly performant.Christoph discovered that xfs_reflink_allocate_cow_range may stumble
over invalid entries in the extent array given that it drops the ilock
but still expects the index to be stable. Simple fixing it to a new
lookup for every iteration still isn't correct given that
xfs_bmapi_allocate will trigger a BUG_ON() if hitting a hole, and
there is nothing preventing a xfs_bunmapi_cow call removing extents
once we dropped the ilock either.This patch duplicates the inner loop of xfs_bmapi_allocate into a
helper for xfs_reflink_allocate_cow_range so that it can be done under
the same ilock critical section as our CoW fork delayed allocation.
The directio CoW warts will be revisited in a later patch.Signed-off-by: Darrick J. Wong
Signed-off-by: Christoph Hellwig -
After the write component of a copy-write operation finishes, clean up
the bookkeeping left behind. On error, we simply free the new blocks
and pass the error up. If we succeed, however, then we must remove
the old data fork mapping and move the cow fork mapping to the data
fork.Signed-off-by: Darrick J. Wong
[hch: Call the CoW failure function during xfs_cancel_ioend]
Signed-off-by: Christoph Hellwig
05 Oct, 2016
3 commits
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Modify the writepage handler to find and convert pending delalloc
extents to real allocations. Furthermore, when we're doing non-cow
writes to a part of a file that already has a CoW reservation (the
cowextsz hint that we set up in a subsequent patch facilitates this),
promote the write to copy-on-write so that the entire extent can get
written out as a single extent on disk, thereby reducing post-CoW
fragmentation.Christoph moved the CoW support code in _map_blocks to a separate helper
function, refactored other functions, and reduced the number of CoW fork
lookups, so I merged those changes here to reduce churn.Signed-off-by: Darrick J. Wong
Signed-off-by: Christoph Hellwig -
Wire up iomap_begin to detect shared extents and create delayed allocation
extents in the CoW fork:1) Check if we already have an extent in the COW fork for the area.
If so nothing to do, we can move along.
2) Look up block number for the current extent, and if there is none
it's not shared move along.
3) Unshare the current extent as far as we are going to write into it.
For this we avoid an additional COW fork lookup and use the
information we set aside in step 1) above.
4) Goto 1) unless we've covered the whole range.Last but not least, this updates the xfs_reflink_reserve_cow_range calling
convention to pass a byte offset and length, as that is what both callers
expect anyway. This patch has been refactored considerably as part of the
iomap transition.Signed-off-by: Darrick J. Wong
Signed-off-by: Christoph Hellwig -
Introduce a new in-core fork for storing copy-on-write delalloc
reservations and allocated extents that are in the process of being
written out.Signed-off-by: Darrick J. Wong
Reviewed-by: Christoph Hellwig