Commit Graph

33 Commits

Author SHA1 Message Date
Darrick J. Wong
f34061f554 xfs: pass explicit mount pointer to rtalloc query functions
Pass an explicit xfs_mount pointer to the rtalloc query functions so
that they can support transactionless queries.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2022-04-12 06:49:41 +10:00
Darrick J. Wong
eba0549bc7 xfs: don't generate selinux audit messages for capability testing
There are a few places where we test the current process' capability set
to decide if we're going to be more or less generous with resource
acquisition for a system call.  If the process doesn't have the
capability, we can continue the call, albeit in a degraded mode.

These are /not/ the actual security decisions, so it's not proper to use
capable(), which (in certain selinux setups) causes audit messages to
get logged.  Switch them to has_capability_noaudit.

Fixes: 7317a03df7 ("xfs: refactor inode ownership change transaction/inode/quota allocation idiom")
Fixes: ea9a46e1c4 ("xfs: only return detailed fsmap info if the caller has CAP_SYS_ADMIN")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
2022-03-09 10:32:06 -08:00
Dave Chinner
38c26bfd90 xfs: replace xfs_sb_version checks with feature flag checks
Convert the xfs_sb_version_hasfoo() to checks against
mp->m_features. Checks of the superblock itself during disk
operations (e.g. in the read/write verifiers and the to/from disk
formatters) are not converted - they operate purely on the
superblock state. Everything else should use the mount features.

Large parts of this conversion were done with sed with commands like
this:

for f in `git grep -l xfs_sb_version_has fs/xfs/*.c`; do
	sed -i -e 's/xfs_sb_version_has\(.*\)(&\(.*\)->m_sb)/xfs_has_\1(\2)/' $f
done

With manual cleanups for things like "xfs_has_extflgbit" and other
little inconsistencies in naming.

The result is ia lot less typing to check features and an XFS binary
size reduced by a bit over 3kB:

$ size -t fs/xfs/built-in.a
	text	   data	    bss	    dec	    hex	filenam
before	1130866  311352     484 1442702  16038e (TOTALS)
after	1127727  311352     484 1439563  15f74b (TOTALS)

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: Darrick J. Wong <djwong@kernel.org>
2021-08-19 10:07:12 -07:00
Darrick J. Wong
159eb69dba xfs: make the record pointer passed to query_range functions const
The query_range functions are supposed to call a caller-supplied
function on each record found in the dataset.  These functions don't
own the memory storing the record, so don't let them change the record.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2021-08-18 18:46:01 -07:00
Darrick J. Wong
7e1826e05b xfs: make fsmap backend function key parameters const
There are several GETFSMAP backend functions for XFS to cover the three
devices and various feature support.  Each of these functions are passed
pointers to the low and high keys for the dataset that userspace
requested, and a pointer to scratchpad variables that are used to
control the iteration and fill out records.  The scratchpad data can be
changed arbitrarily, but the keys are supposed to remain unchanged (and
under the control of the outermost loop in xfs_getfsmap).

Unfortunately, the data and rt backends modify the keys that are passed
in from the main control loop, which causes subsequent calls to return
incorrect query results.  Specifically, each of those two functions set
the block number in the high key to the size of their respective device.
Since fsmap results are sorted in device number order, if the lower
numbered device is smaller than the higher numbered device, the first
function will set the high key to the small size, and the key remains
unchanged as it is passed into the function for the higher numbered
device.  The second function will then fail to return all of the results
for the dataset that userspace is asking for because the keyspace is
incorrectly constrained.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
2021-08-18 18:46:00 -07:00
Darrick J. Wong
9ab72f2227 xfs: fix off-by-one error when the last rt extent is in use
The fsmap implementation for realtime devices uses the gap between
info->next_daddr and a free rtextent reported by xfs_rtalloc_query_range
to feed userspace fsmap records with an "unknown" owner.  We use this
trick to report to userspace when the last rtextent in the filesystem is
in use by synthesizing a null rmap record starting at the next block
after the query range.

Unfortunately, there's a minor accounting bug in the way that we
construct the null rmap record.  Originally, ahigh.ar_startext contains
the last rtextent for which the user wants records.  It's entirely
possible that number is beyond the end of the rt volume, so the location
synthesized rmap record /must/ be constrained to the minimum of the high
key and the number of extents in the rt volume.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
2021-08-18 18:46:00 -07:00
Dave Chinner
50f02fe333 xfs: remove agno from btree cursor
Now that everything passes a perag, the agno is not needed anymore.
Convert all the users to use pag->pag_agno instead and remove the
agno from the cursor. This was largely done as an automated search
and replace.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2021-06-02 10:48:24 +10:00
Dave Chinner
289d38d22c xfs: convert allocbt cursors to use perags
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2021-06-02 10:48:24 +10:00
Dave Chinner
a81a06211f xfs: convert refcount btree cursor to use perags
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2021-06-02 10:48:24 +10:00
Dave Chinner
fa9c3c1973 xfs: convert rmap btree cursor to using a perag
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2021-06-02 10:48:24 +10:00
Dave Chinner
be9fb17d88 xfs: add a perag to the btree cursor
Which will eventually completely replace the agno in it.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
2021-06-02 10:48:24 +10:00
Dave Chinner
58d43a7e32 xfs: pass perags around in fsmap data dev functions
Needs a [from, to] ranged AG walk, and the perag to be stuffed into
the info structure for callouts to use.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2021-06-02 10:48:24 +10:00
Darrick J. Wong
e424aa5f54 xfs: drop freeze protection when running GETFSMAP
A recent log refactoring patchset from Brian Foster relaxed fsfreeze
behavior with regards to the buffer cache -- now freeze only waits for
pending buffer IO to finish, and does not try to drain the buffer cache
LRU.  As a result, fsfreeze should no longer stall indefinitely while
fsmap runs.  Drop the sb_start_write calls around fsmap invocations.

While we're cleaning things, add a comment to the xfs_trans_alloc_empty
call explaining why we're running around with empty transactions.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2021-03-24 10:36:05 -07:00
Darrick J. Wong
8ffa90e114 xfs: fix deadlock and streamline xfs_getfsmap performance
Refactor xfs_getfsmap to improve its performance: instead of indirectly
calling a function that copies one record to userspace at a time, create
a shadow buffer in the kernel and copy the whole array once at the end.
On the author's computer, this reduces the runtime on his /home by ~20%.

This also eliminates a deadlock when running GETFSMAP against the
realtime device.  The current code locks the rtbitmap to create
fsmappings and copies them into userspace, having not released the
rtbitmap lock.  If the userspace buffer is an mmap of a sparse file that
itself resides on the realtime device, the write page fault will recurse
into the fs for allocation, which will deadlock on the rtbitmap lock.

Fixes: 4c934c7dd6 ("xfs: report realtime space information via the rtbitmap")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
2020-10-07 08:40:29 -07:00
Darrick J. Wong
acd1ac3aa2 xfs: limit entries returned when counting fsmap records
If userspace asked fsmap to count the number of entries, we cannot
return more than UINT_MAX entries because fmh_entries is u32.
Therefore, stop counting if we hit this limit or else we will waste time
to return truncated results.

Fixes: e89c041338 ("xfs: implement the GETFSMAP ioctl")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
2020-10-07 08:40:29 -07:00
Darrick J. Wong
27fb5a72f5 xfs: prohibit fs freezing when using empty transactions
I noticed that fsfreeze can take a very long time to freeze an XFS if
there happens to be a GETFSMAP caller running in the background.  I also
happened to notice the following in dmesg:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 43492 at fs/xfs/xfs_super.c:853 xfs_quiesce_attr+0x83/0x90 [xfs]
Modules linked in: xfs libcrc32c ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 ip_set_hash_ip ip_set_hash_net xt_tcpudp xt_set ip_set_hash_mac ip_set nfnetlink ip6table_filter ip6_tables bfq iptable_filter sch_fq_codel ip_tables x_tables nfsv4 af_packet [last unloaded: xfs]
CPU: 2 PID: 43492 Comm: xfs_io Not tainted 5.6.0-rc4-djw #rc4
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-1ubuntu1 04/01/2014
RIP: 0010:xfs_quiesce_attr+0x83/0x90 [xfs]
Code: 7c 07 00 00 85 c0 75 22 48 89 df 5b e9 96 c1 00 00 48 c7 c6 b0 2d 38 a0 48 89 df e8 57 64 ff ff 8b 83 7c 07 00 00 85 c0 74 de <0f> 0b 48 89 df 5b e9 72 c1 00 00 66 90 0f 1f 44 00 00 41 55 41 54
RSP: 0018:ffffc900030f3e28 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff88802ac54000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81e4a6f0 RDI: 00000000ffffffff
RBP: ffff88807859f070 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000010 R12: 0000000000000000
R13: ffff88807859f388 R14: ffff88807859f4b8 R15: ffff88807859f5e8
FS:  00007fad1c6c0fc0(0000) GS:ffff88807e000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0c7d237000 CR3: 0000000077f01003 CR4: 00000000001606a0
Call Trace:
 xfs_fs_freeze+0x25/0x40 [xfs]
 freeze_super+0xc8/0x180
 do_vfs_ioctl+0x70b/0x750
 ? __fget_files+0x135/0x210
 ksys_ioctl+0x3a/0xb0
 __x64_sys_ioctl+0x16/0x20
 do_syscall_64+0x50/0x1a0
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

These two things appear to be related.  The assertion trips when another
thread initiates a fsmap request (which uses an empty transaction) after
the freezer waited for m_active_trans to hit zero but before the the
freezer executes the WARN_ON just prior to calling xfs_log_quiesce.

The lengthy delays in freezing happen because the freezer calls
xfs_wait_buftarg to clean out the buffer lru list.  Meanwhile, the
GETFSMAP caller is continuing to grab and release buffers, which means
that it can take a very long time for the buffer lru list to empty out.

We fix both of these races by calling sb_start_write to obtain freeze
protection while using empty transactions for GETFSMAP and for metadata
scrubbing.  The other two users occur during mount, during which time we
cannot fs freeze.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
2020-03-26 08:19:24 -07:00
Dave Chinner
576af73228 xfs: convert btree cursor ag-private member name
bc_private.a -> bc_ag conversion via script:

`sed -i 's/bc_private\.a/bc_ag/g' fs/xfs/*[ch] fs/xfs/*/*[ch]`

And then revert the change to the bc_ag #define in
fs/xfs/libxfs/xfs_btree.h manually.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
2020-03-13 10:37:14 -07:00
Darrick J. Wong
110f09cb70 xfs: add missing assert in xfs_fsmap_owner_from_rmap
The fsmap handler shouldn't fail silently if the rmap code ever feeds it
a special owner number that isn't known to the fsmap handler.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2019-11-05 08:28:27 -08:00
Darrick J. Wong
39ee2239a5 xfs: remove all *_ITER_CONTINUE values
Iterator functions already use 0 to signal "continue iterating", so get
rid of the #defines and just do it directly.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
2019-08-30 22:43:56 -07:00
Darrick J. Wong
e7ee96dfb8 xfs: remove all *_ITER_ABORT values
Use -ECANCELED to signal "stop iterating" instead of these magical
*_ITER_ABORT values, since it's duplicative.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
2019-08-29 21:22:41 -07:00
Eric Sandeen
250d4b4c40 xfs: remove unused header files
There are many, many xfs header files which are included but
unneeded (or included twice) in the xfs code, so remove them.

nb: xfs_linux.h includes about 9 headers for everyone, so those
explicit includes get removed by this.  I'm not sure what the
preference is, but if we wanted explicit includes everywhere,
a followup patch could remove those xfs_*.h includes from
xfs_linux.h and move them into the files that need them.
Or it could be left as-is.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2019-06-28 19:30:43 -07:00
Darrick J. Wong
0b04b6b875 xfs: trivial xfs_btree_del_cursor cleanups
The error argument to xfs_btree_del_cursor already understands the
"nonzero for error" semantics, so remove pointless error testing in the
callers and pass it directly.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2018-07-23 09:08:00 -07:00
Brian Foster
ed7ef8e55c xfs: remove unused btree cursor bc_private.a.dfops field
The xfs_btree_cur.bc_private.a.dfops field is only ever initialized
by the refcountbt cursor init function. The only caller of that
function with a non-NULL dfops is from deferred completion context,
which already has attached to ->t_dfops.

In addition to that, the only actual reference of a.dfops is the
cursor duplication function, which means the field is effectively
unused.

Remove the dfops field from the bc_private.a union. Any future users
can acquire the dfops from the transaction. This patch does not
change behavior.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-07-11 22:26:17 -07:00
Darrick J. Wong
232d0a24b0 xfs: fix uninitialized field in rtbitmap fsmap backend
Initialize the extent count field of the high key so that when we use
the high key to synthesize an 'unknown owner' record (i.e. used space
record) at the end of the queried range we have a field with which to
compute rm_blockcount.  This is not strictly necessary because the
synthesizer never uses the rm_blockcount field, but we can shut up the
static code analysis anyway.

Coverity-id: 1437358
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2018-06-24 11:56:36 -07:00
Dave Chinner
0b61f8a407 xfs: convert to SPDX license tags
Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
	echo $f
	cat $f | awk -f hdr.awk > $f.new
	mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
	hdr = 1.0
	tag = "GPL-2.0"
	str = ""
}

/^ \* This program is free software/ {
	hdr = 2.0;
	next
}

/any later version./ {
	tag = "GPL-2.0+"
	next
}

/^ \*\// {
	if (hdr > 0.0) {
		print "// SPDX-License-Identifier: " tag
		print str
		print $0
		str=""
		hdr = 0.0
		next
	}
	print $0
	next
}

/^ \* / {
	if (hdr > 1.0)
		next
	if (hdr > 0.0) {
		if (str != "")
			str = str "\n"
		str = str $0
		next
	}
	print $0
	next
}

/^ \*/ {
	if (hdr > 0.0)
		next
	print $0
	next
}

// {
	if (hdr > 0.0) {
		if (str != "")
			str = str "\n"
		str = str $0
		next
	}
	print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-06-06 14:17:53 -07:00
Darrick J. Wong
a0e5c435ba xfs: fix xfs_rtalloc_rec units
All the realtime allocation functions deal with space on the rtdev in
units of realtime extents.  However, struct xfs_rtalloc_rec confusingly
uses the word 'block' in the name, even though they're really extents.

Fix the naming problem and fix all the unit handling problems in the two
existing users.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
2018-06-01 09:00:16 -07:00
Arnd Bergmann
785545c898 xfs: move two more RT specific functions into CONFIG_XFS_RT
The last cleanup introduced two harmless warnings:

fs/xfs/xfs_fsmap.c:480:1: warning: '__xfs_getfsmap_rtdev' defined but not used
fs/xfs/xfs_fsmap.c:372:1: warning: 'xfs_getfsmap_rtdev_rtbitmap_helper' defined but not used

This moves those two functions as well.

Fixes: bb9c2e5433 ("xfs: move more RT specific code under CONFIG_XFS_RT")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2017-10-16 12:26:50 -07:00
Dave Chinner
bb9c2e5433 xfs: move more RT specific code under CONFIG_XFS_RT
Various utility functions and interfaces that iterate internal
devices try to reference the realtime device even when RT support is
not compiled into the kernel.

Make sure this code is excluded from the CONFIG_XFS_RT=n build,
and where appropriate stub functions to return fatal errors if
they ever get called when RT support is not present.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2017-10-11 10:21:06 -07:00
Darrick J. Wong
ea9a46e1c4 xfs: only return detailed fsmap info if the caller has CAP_SYS_ADMIN
There were a number of handwaving complaints that one could "possibly"
use inode numbers and extent maps to fingerprint a filesystem hosting
multiple containers and somehow use the information to guess at the
contents of other containers and attack them.  Despite the total lack of
any demonstration that this is actually possible, it's easier to
restrict access now and broaden it later, so use the rmapbt fsmap
backends only if the caller has CAP_SYS_ADMIN.  Unprivileged users will
just have to make do with only getting the free space and static
metadata placement information.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
2017-05-16 12:26:16 -07:00
Christoph Hellwig
fad5656b22 xfs: use NULL instead of 0 to initialize a pointer in xfs_getfsmap
Found by sparse.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2017-04-25 09:40:41 -07:00
Darrick J. Wong
4c934c7dd6 xfs: report realtime space information via the rtbitmap
Use the realtime bitmap to return free space information via getfsmap.
Eventually this will be superseded by the realtime rmapbt code.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
2017-04-03 15:18:18 -07:00
Darrick J. Wong
a1cae7283d xfs: have getfsmap fall back to the freesp btrees when rmap is not present
If the reverse-mapping btree isn't available, fall back to the
free space btrees to provide partial reverse mapping information.
The online scrub tool can make use of even partial information to
speed up the data block scan.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
2017-04-03 15:18:18 -07:00
Darrick J. Wong
e89c041338 xfs: implement the GETFSMAP ioctl
Introduce a new ioctl that uses the reverse mapping btree to return
information about the physical layout of the filesystem.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
2017-04-03 15:18:17 -07:00