xfs_io(8) System Manager's Manual xfs_io(8)
NAME
xfs_io - debug the I/O path of an XFS filesystem
SYNOPSIS
xfs_io [ -adfimrRstxT ] [ -c cmd ] ... [ -C cmd ] ... [ -p prog ] [
file ]
xfs_io -V
DESCRIPTION
xfs_io is a debugging tool like xfs_db(8), but is aimed at examining
the regular file I/O paths rather than the raw XFS volume itself.
These code paths include not only the obvious read/write/mmap inter-
faces for manipulating files, but also cover all of the XFS extensions
(such as space preallocation, additional inode flags, etc).
OPTIONS
xfs_io commands may be run interactively (the default) or as arguments
on the command line. Interactive mode always runs commands on the cur-
rent open file, whilst commands run from the command line may be
repeated on all open files rather than just the current open file. In
general, open file iteration will occur for commands that operate on
file content or state. In contrast, commands that operate on filesystem
or system-wide state will only be run on the current file regardless of
how many files are currently open. Multiple arguments may be given on
the command line and they are run in the sequence given. The program
exits one all commands have been run.
-c cmd Run the specified command on all currently open files. To
maintain compatibility with historical usage, commands that
can not be run on all open files will still be run but only
execute once on the current open file. Multiple -c arguments
may be given and may be interleaved on the command line in
any order with -C commands.
-C cmd Run the specified command only on the current open file.
Multiple -C arguments may be given and may be interleaved on
the command line in any order with -c commands.
-p prog Set the program name for prompts and some error messages, the
default value is xfs_io.
-f Create file if it does not already exist.
-r Open file read-only, initially. This is required if file is
immutable or append-only.
-i Start an idle thread. The purpose of this idle thread is to
test io from a multi threaded process. With single threaded
process, the file table is not shared and file structs are
not reference counted. Spawning an idle thread can help
detecting file struct reference leaks.
-x Expert mode. Dangerous commands are only available in this
mode. These commands also tend to require additional privi-
leges.
-V Prints the version number and exits.
The other open(2) options described below are also available from the
command line.
CONCEPTS
xfs_io maintains a number of open files and memory mappings. Files can
be initially opened on the command line (optionally), and additional
files can also be opened later.
xfs_io commands can be broken up into three groups. Some commands are
aimed at doing regular file I/O - read, write, sync, space prealloca-
tion, etc.
The second set of commands exist for manipulating memory mapped regions
of a file - mapping, accessing, storing, unmapping, flushing, etc.
The remaining commands are for the navigation and display of data
structures relating to the open files, mappings, and the filesystems
where they reside.
Many commands have extensive online help. Use the help command for more
details on any command.
FILE I/O COMMANDS
file [ N ]
Display a list of all open files and (optionally) switch to an
alternate current open file.
open [[ -acdfrstRTPL ] path ]
Closes the current file, and opens the file specified by path
instead. Without any arguments, displays statistics about the
current file - see the stat command.
-a opens append-only (O_APPEND).
-d opens for direct I/O (O_DIRECT).
-f creates the file if it doesn't already exist (O_CREAT).
-r opens read-only (O_RDONLY).
-s opens for synchronous I/O (O_SYNC).
-t truncates on open (O_TRUNC).
-n opens in non-blocking mode if possible (O_NONBLOCK).
-T create a temporary file not linked into the filesystem
namespace (O_TMPFILE). The pathname passed must refer to
a directory which is treated as virtual parent for the
newly created invisible file. Can not be used together
with the -r option.
-R marks the file as a realtime XFS file after opening it,
if it is not already marked as such.
-P opens the path as a referent only (O_PATH). This is
incompatible with other flags specifying other O_xxx
flags apart from -L.
-L doesn't follow symlinks (O_NOFOLLOW). This is incompati-
ble with other flags specifying other O_xxx flags apart
from -P.
o See the open command.
close Closes the current open file, marking the next open file as cur-
rent (if one exists).
c See the close command.
chmod -r | -w
Change the mode of the currently open file. The -r option will
set the file permissions to read-only (0444), whilst the -w
option will set the file permissions to read-write (0644). This
allows xfs_io to set up mismatches between the file permissions
and the open file descriptor read/write mode to exercise permis-
sion checks inside various syscalls.
pread [ -b bsize ] [ -v ] [ -FBR [ -Z seed ] ] [ -V vectors ] offset
length
Reads a range of bytes in a specified blocksize from the given
offset.
-b can be used to set the blocksize into which the read(2)
requests will be split. The default blocksize is 4096
bytes.
-v dump the contents of the buffer after reading, by default
only the count of bytes actually read is dumped.
-F read the buffers in a forwards sequential direction.
-B read the buffers in a reserve sequential direction.
-R read the buffers in the give range in a random order.
-Z seed
specify the random number seed used for random reads.
-V vectors
Use the vectored IO read syscall preadv(2) with a number
of blocksize length iovecs. The number of iovecs is set
by the vectors parameter.
r See the pread command.
pwrite [ -i file ] [ -dDwNOW ] [ -s skip ] [ -b size ] [ -S seed ] [
-FBR [ -Z zeed ] ] [ -V vectors ] offset length
Writes a range of bytes in a specified blocksize from the given
offset. The bytes written can be either a set pattern or read
in from another file before writing.
-i allows an input file to be specified as the source of the
data to be written.
-d causes direct I/O, rather than the usual buffered I/O, to
be used when reading the input file.
-w call fdatasync(2) once all writes are complete (included
in timing results)
-N Perform the pwritev2(2) call with RWF_NOWAIT.
-D Perform the pwritev2(2) call with RWF_DSYNC.
-O perform pwrite once and return the (maybe partial) bytes
written.
-W call fsync(2) once all writes are complete (included in
timing results)
-s specifies the number of bytes to skip from the start of
the input file before starting to read.
-b used to set the blocksize into which the write(2)
requests will be split. The default blocksize is 4096
bytes.
-S used to set the (repeated) fill pattern which is used
when the data to write is not coming from a file. The
default buffer fill pattern value is 0xcdcdcdcd.
-F write the buffers in a forwards sequential direction.
-B write the buffers in a reserve sequential direction.
-R write the buffers in the give range in a random order.
-Z seed
specify the random number seed used for random write
-V vectors
Use the vectored IO write syscall pwritev(2) with a num-
ber of blocksize length iovecs. The number of iovecs is
set by the vectors parameter.
w See the pwrite command.
bmap [ -adelpv ] [ -n nx ]
Prints the block mapping for the current open file. Refer to the
xfs_bmap(8) manual page for complete documentation.
fiemap [ -alv ] [ -n nx ] [ offset [ len ]]
Prints the block mapping for the current open file using the
fiemap ioctl. Options behave as described in the xfs_bmap(8)
manual page.
Optionally, this command also supports passing the start offset
from where to begin the mapping and the length of that region.
The kernel will return any full extents which intersect with the
requested range, and the fiemap command will print them in their
entirety. If the requested range starts or ends in a hole,
fiemap will print the hole, truncated to the requested range.
extsize [ -R | -D ] [ value ]
Display and/or modify the preferred extent size used when allo-
cating space for the currently open file. If the -R option is
specified, a recursive descent is performed for all directory
entries below the currently open file (-D can be used to
restrict the output to directories only). If the target file is
a directory, then the inherited extent size is set for that
directory (new files created in that directory inherit that
extent size). The value should be specified in bytes, or using
one of the usual units suffixes (k, m, g, b, etc). The extent
size is always reported in units of bytes.
cowextsize [ -R | -D ] [ value ]
Display and/or modify the preferred copy-on-write extent size
used when allocating space for the currently open file. If the
-R option is specified, a recursive descent is performed for all
directory entries below the currently open file (-D can be used
to restrict the output to directories only). If the target file
is a directory, then the inherited CoW extent size is set for
that directory (new files created in that directory inherit that
CoW extent size). The value should be specified in bytes, or
using one of the usual units suffixes (k, m, g, b, etc). The
extent size is always reported in units of bytes.
allocsp size 0
Sets the size of the file to size and zeroes any additional
space allocated using the XFS_IOC_ALLOCSP/XFS_IOC_FREESP system
call described in the xfsctl(3) manual page. allocsp and freesp
do exactly the same thing.
freesp size 0
See the allocsp command.
fadvise [ -r | -s | [[ -d | -n | -w ] offset length ]]
On platforms which support it, allows hints be given to the sys-
tem regarding the expected I/O patterns on the file. The range
arguments are required by some advise commands ([*] below), and
the others must have no range arguments. With no arguments, the
POSIX_FADV_NORMAL advice is implied (default readahead).
-d the data will not be accessed again in the near future
(POSIX_FADV_DONTNEED[*]).
-n data will be accessed once and not be reused
(POSIX_FADV_NOREUSE[*]).
-r expect access to data in random order (POSIX_FADV_RAN-
DOM), which sets readahead to zero.
-s expect access to data in sequential order
(POSIX_FADV_SEQUENTIAL), which doubles the default reada-
head on the file.
-w advises the specified data will be needed again
(POSIX_FADV_WILLNEED[*]) which forces the maximum reada-
head.
fdatasync
Calls fdatasync(2) to flush the file's in-core data to disk.
fsync Calls fsync(2) to flush all in-core file state to disk.
s See the fsync command.
sync_range [ -a | -b | -w ] offset length
On platforms which support it, allows control of syncing a range
of the file to disk. With no options, SYNC_FILE_RANGE_WRITE is
implied on the range supplied.
-a wait for IO in the given range to finish after writing
(SYNC_FILE_RANGE_WAIT_AFTER).
-b wait for IO in the given range to finish before writing
(SYNC_FILE_RANGE_WAIT_BEFORE).
-w start writeback of dirty data in the given range
(SYNC_FILE_RANGE_WRITE).
sync Calls sync(2) to flush all filesystems' in-core data to disk.
syncfs Calls syncfs(2) to flush this filesystem's in-core data to disk.
resvsp offset length
Allocates reserved, unwritten space for part of a file using the
XFS_IOC_RESVSP system call described in the xfsctl(3) manual
page.
unresvsp offset length
Frees reserved space for part of a file using the
XFS_IOC_UNRESVSP system call described in the xfsctl(3) manual
page.
falloc [ -k ] offset length
Allocates reserved, unwritten space for part of a file using the
fallocate routine as described in the fallocate(2) manual page.
-k will set the FALLOC_FL_KEEP_SIZE flag as described in
fallocate(2).
fcollapse offset length
Call fallocate with FALLOC_FL_COLLAPSE_RANGE flag as described
in the fallocate(2) manual page to de-allocates blocks and elim-
inates the hole created in this process by shifting data blocks
into the hole.
finsert offset length
Call fallocate with FALLOC_FL_INSERT_RANGE flag as described in
the fallocate(2) manual page to create the hole by shifting data
blocks.
fpunch offset length
Punches (de-allocates) blocks in the file by calling fallocate
with the FALLOC_FL_PUNCH_HOLE flag as described in the fallo-
cate(2) manual page.
funshare offset length
Call fallocate with FALLOC_FL_UNSHARE_RANGE flag as described in
the fallocate(2) manual page to unshare all shared blocks within
the range.
fzero [ -k ] offset length
Call fallocate with FALLOC_FL_ZERO_RANGE flag as described in
the fallocate(2) manual page to allocate and zero blocks within
the range. With the -k option, use the FALLOC_FL_KEEP_SIZE flag
as well.
zero offset length
Call xfsctl with XFS_IOC_ZERO_RANGE as described in the
xfsctl(3) manual page to allocate and zero blocks within the
range.
truncate offset
Truncates the current file at the given offset using ftrun-
cate(2).
sendfile -i srcfile | -f N [ offset length ]
On platforms which support it, allows a direct in-kernel copy
between two file descriptors. The current open file is the tar-
get, the source must be specified as another open file (-f) or
by path (-i).
readdir [ -v ] [ -o offset ] [ -l length ]
Read a range of directory entries from a given offset of a
directory.
-v verbose mode - dump dirent content as defined in read-
dir(3)
-o specify starting offset
-l specify total length to read (in bytes)
seek -a | -d | -h [ -r ] [ -s ] offset
On platforms that support the lseek(2) SEEK_DATA and SEEK_HOLE
options, display the offsets of the specified segments.
-a Display both data and hole segments starting at the spec-
ified offset.
-d Display the data segment starting at the specified off-
set.
-h Display the hole segment starting at the specified off-
set.
-r Recursively display all the specified segments starting
at the specified offset.
-s Display the starting lseek(2) offset. This offset will be
a calculated value when both data and holes are displayed
together or performing a recusively display.
reflink [ -C ] [ -q ] src_file [src_offset dst_offset length]
On filesystems that support the FICLONERANGE or
BTRFS_IOC_CLONE_RANGE ioctls, map length bytes at offset
dst_offset in the open file to the same physical blocks that are
mapped at offset src_offset in the file src_file , replacing any
contents that may already have been there. If a program writes
into a reflinked block range of either file, the dirty blocks
will be cloned, written to, and remapped ("copy on write") in
the affected file, leaving the other file(s) unchanged. If
src_offset, dst_offset, and length are omitted, all contents of
src_file will be reflinked into the open file.
-C Print timing statistics in a condensed format.
-q Do not print timing statistics at all.
dedupe [ -C ] [ -q ] src_file src_offset dst_offset length
On filesystems that support the FIDEDUPERANGE or
BTRFS_IOC_FILE_EXTENT_SAME ioctls, map length bytes at offset
dst_offset in the open file to the same physical blocks that are
mapped at offset src_offset in the file src_file , but only if
the contents of both ranges are identical. This is known as
block-based deduplication. If a program writes into a reflinked
block range of either file, the dirty blocks will be cloned,
written to, and remapped ("copy on write") in the affected file,
leaving the other file(s) unchanged.
-C Print timing statistics in a condensed format.
-q Do not print timing statistics at all.
copy_range [ -s src_offset ] [ -d dst_offset ] [ -l length ] src_file
On filesystems that support the copy_file_range(2) system call,
copies data from the src_file into the open file. If src_off-
set, dst_offset, and length are omitted the contents of src_file
will be copied to the beginning of the open file, overwriting
any data already there.
-s Copy data from src_file beginning from src_offset.
-d Copy data into the open file beginning at dst_offset.
-l Copy up to length bytes of data.
swapext donor_file
Swaps extent forks between files. The current open file is the
target. The donor file is specified by path. Note that file data
is not copied (file content moves with the fork(s)).
set_encpolicy [ -c mode ] [ -n mode ] [ -f flags ] [ -v version ] [
keydesc ]
On filesystems that support encryption, assign an encryption
policy to the current file. keydesc is a 16-byte hex string
which identifies the encryption key to use. If not specified, a
"default" key descriptor of all 0's will be used.
-c mode
contents encryption mode (e.g. AES-256-XTS)
-n mode
filenames encryption mode (e.g. AES-256-CTS)
-f flags
policy flags (numeric)
-v version
version of policy structure (numeric)
get_encpolicy
On filesystems that support encryption, display the encryption
policy of the current file.
lsattr [ -R | -D | -a | -v ]
List extended inode flags on the currently open file. If the -R
option is specified, a recursive descent is performed for all
directory entries below the currently open file (-D can be used
to restrict the output to directories only). This is a depth
first descent, it does not follow symlinks and it also does not
cross mount points.
chattr [ -R | -D ] [ +/-riasAdtPneEfSxC ]
Change extended inode flags on the currently open file. The -R
and -D options have the same meaning as above. The mapping
between each letter and the inode flags (refer to xfsctl(3) for
the full list) is available via the help command.
flink path
Link the currently open file descriptor into the filesystem
namespace.
stat [ -v|-r ]
Selected statistics from stat(2) and the XFS_IOC_GETXATTR system
call on the current file. If the -v option is specified, the
atime (last access), mtime (last modify), and ctime (last
change) timestamps are also displayed. The -r option dumps raw
fields from the stat structure.
statx [ -v|-r ][ -m basic | -m all | -m <mask> ][ -FD ]
Selected statistics from stat(2) and the XFS_IOC_GETXATTR system
call on the current file.
-v Show timestamps.
-r Dump raw statx structure values.
-m basic
Set the field mask for the statx call to
STATX_BASIC_STATS.
-m all
Set the the field mask for the statx call to STATX_ALL
(default).
-m <mask>
Specify a numeric field mask for the statx call.
-F Force the attributes to be synced with the server.
-D Don't sync attributes with the server.
chproj [ -R|-D ]
Modifies the project identifier associated with the current
path. The -R option will recursively descend if the current path
is a directory. The -D option will also recursively descend,
only setting modifying projects on subdirectories. See the
xfs_quota(8) manual page for more information about project
identifiers.
lsproj [ -R|-D ]
Displays the project identifier associated with the current
path. The -R and -D options behave as described above, in
chproj.
parent [ -cpv ]
By default this command prints out the parent inode numbers,
inode generation numbers and basenames of all the hardlinks
which point to the inode of the current file.
-p the output is similar to the default output except path-
names up to the mount-point are printed out instead of
the component name.
-c the file's filesystem will check all the parent
attributes for consistency.
-v verbose output will be printed.
[NOTE: Not currently operational on Linux.]
utimes atime_sec atime_nsec mtime_sec mtime_nsec
The utimes command changes the atime and mtime of the current
file. sec uses UNIX timestamp notation and is the seconds
elapsed since 1970-01-01 00:00:00 UTC. nsec is the nanoseconds
since the sec. This value needs to be in the range 0-999999999
with UTIME_NOW and UTIME_OMIT being exceptions. Each (sec,
nsec) pair constitutes a single timestamp value.
MEMORY MAPPED I/O COMMANDS
mmap [ N | [[ -rwxS ] [-s size ] offset length ]]
With no arguments, mmap shows the current mappings. Specifying a
single numeric argument N sets the current mapping. If two argu-
ments are specified (a range specified by offset and length), a
new mapping is created spanning the range, and the protection
mode can be given as a combination of PROT_READ (-r), PROT_WRITE
(-w), and PROT_EXEC (-x). The mapping will be created with the
MAP_SHARED flag by default, or with the Linux specific (MAP_SYNC
| MAP_SHARED_VALIDATE) flags if -S is given. -s size is used to
do a mmap(size) && munmap(size) operation at first, try to
reserve some extendible free memory space, if size is bigger
than length parameter. But there's not guarantee that the memory
after length ( up to size ) will stay free. e.g. "mmap -rw -s
8192 1024" will mmap 0 ~ 1024 bytes memory, but try to reserve
1024 ~ 8192 free space(no guarantee). This free space will help-
ful for "mremap 8192" without MREMAP_MAYMOVE flag.
mm See the mmap command.
mremap [ -f <new_address> ] [ -m ] new_length
Changes the current mapping size to new_length. Whether the
mapping may be moved is controlled by the flags passed;
MREMAP_FIXED (-f), or MREMAP_MAYMOVE (-m). new_length specifies
a page-aligned address to which the mapping must be moved. It
can be set to 139946004389888, 4096k or 1g etc.
mrm See the mremap command.
munmap Unmaps the current memory mapping.
mu See the munmap command.
mread [ -f | -v ] [ -r ] [ offset length ]
Accesses a segment of the current memory mapping, optionally
dumping it to the standard output stream (with -v or -f option)
for inspection. The accesses are performed sequentially from the
start offset by default, but can also be done from the end back-
wards through the mapping if the -r option in specified. The
two verbose modes differ only in the relative offsets they dis-
play, the -f option is relative to file start, whereas -v shows
offsets relative to the start of the mapping.
mr See the mread command.
mwrite [ -r ] [ -S seed ] [ offset length ]
Stores a byte into memory for a range within a mapping. The
default stored value is 'X', repeated to fill the range speci-
fied, but this can be changed using the -S option. The memory
stores are performed sequentially from the start offset by
default, but can also be done from the end backwards through the
mapping if the -r option in specified.
mw See the mwrite command.
msync [ -i ] [ -a | -s ] [ offset length ]
Writes all modified copies of pages over the specified range (or
entire mapping if no range specified) to their backing storage
locations. Also, optionally invalidates (-i) so that subsequent
references to the pages will be obtained from their backing
storage locations (instead of cached copies). The flush can be
done synchronously (-s) or asynchronously (-a).
ms See the msync command.
madvise [ -d | -r | -s | -w ] [ offset length ]
Modifies page cache behavior when operating on the current map-
ping. The range arguments are required by some advise commands
([*] below). With no arguments, the POSIX_MADV_NORMAL advice is
implied (default readahead).
-d the pages will not be needed (POSIX_MADV_DONTNEED[*]).
-r expect random page references (POSIX_MADV_RANDOM), which
sets readahead to zero.
-s expect sequential page references (POSIX_MADV_SEQUEN-
TIAL), which doubles the default readahead on the file.
-w advises the specified pages will be needed again
(POSIX_MADV_WILLNEED[*]) which forces the maximum reada-
head.
mincore
Dumps a list of pages or ranges of pages that are currently in
core, for the current memory mapping.
FILESYSTEM COMMANDS
freeze Suspend all write I/O requests to the filesystem of the current
file. Only available in expert mode and requires privileges.
thaw Undo the effects of a filesystem freeze operation. Only avail-
able in expert mode and requires privileges.
inject [ tag ]
Inject errors into a filesystem to observe filesystem behavior
at specific points under adverse conditions. Without the tag
argument, displays the list of error tags available. Only
available in expert mode and requires privileges.
resblks [ blocks ]
Get and/or set count of reserved filesystem blocks using the
XFS_IOC_GET_RESBLKS or XFS_IOC_SET_RESBLKS system calls. Note
-- this can be useful for exercising out of space behavior.
Only available in expert mode and requires privileges.
shutdown [ -f ]
Force the filesystem to shut down, preventing any further IO.
XFS and other filesystems implement this functionality, although
implementation details may differ slightly. Only available in
expert mode and requires privileges.
By default, the filesystem will not attempt to flush completed
transactions to disk before shutting down the filesystem. This
simulates a disk failure or crash.
-f Force the filesystem to flush all completed transactions
to disk before shutting down, matching XFS behavior when
critical corruption is encountered.
statfs Selected statistics from statfs(2) and the XFS_IOC_FSGEOMETRY
system call on the filesystem where the current file resides.
inode [ [ -n ] number ] [ -v ]
The inode command queries physical information about an inode.
With no arguments, it will return 1 or 0, indicating whether or
not any inode numbers greater than 32 bits are currently in use
in the filesystem. If given an inode number as an argument, the
command will return the same inode number if it is in use, or 0
if not. With -n number , the next used inode number after this
number will be returned, or zero if the supplied inode number is
the highest one in use. With -v the command will also report the
number of bits (32 or 64) used by the inode number printed in
the result; if no inode number was specified on the command
line, the maximum possible inode number in the system will be
printed along with its size.
scrub type [ agnumber | ino gen ]
Scrub internal XFS filesystem metadata. The type parameter
specifies which type of metadata to scrub. For AG metadata, one
AG number must be specified. For file metadata, the scrub is
applied to the open file unless the inode number and generation
number are specified.
repair type [ agnumber | ino gen ]
Repair internal XFS filesystem metadata. The type parameter
specifies which type of metadata to repair. For AG metadata,
one AG number must be specified. For file metadata, the repair
is applied to the open file unless the inode number and genera-
tion number are specified.
label [ -c | -s label ]
On filesystems that support online label manipulation, get, set,
or clear the filesystem label. With no options, print the cur-
rent filesystem label. The -c option clears the filesystem
label by setting it to the null string. The -s label option
sets the filesystem label to label. If the label is longer than
the filesystem will accept, xfs_io will print an error message.
XFS filesystem labels can be at most 12 characters long.
fsmap [ -d | -l | -r ] [ -m | -v ] [ -n nx ] [ start ] [ end ]
Prints the mapping of disk blocks used by the filesystem hosting
the current file. The map lists each extent used by files,
allocation group metadata, journalling logs, and static filesys-
tem metadata, as well as any regions that are unused. Each line
of the listings takes the following form:
extent: major:minor [startblock..endblock]: owner startoff-
set..endoffset length
Static filesystem metadata, allocation group metadata, btrees,
journalling logs, and free space are marked by replacing the
startoffset..endoffset with the appropriate marker. All blocks,
offsets, and lengths are specified in units of 512-byte blocks,
no matter what the filesystem's block size is. The optional
start and end arguments can be used to constrain the output to a
particular range of disk blocks. If these two options are spec-
ified, exactly one of -d, -l, or -r must also be set.
-d Display only extents from the data device. This
option only applies for XFS filesystems.
-l Display only extents from the external log device.
This option only applies to XFS filesystems.
-r Display only extents from the realtime device. This
option only applies to XFS filesystems.
-m Display results in a machine readable format (CSV).
This option is not compatible with the -v flag. The
columns of the output are: extent number, device
major, device minor, physical start, physical end,
owner, offset start, offset end, length. The start,
end, and length numbers are provided in units of 512b.
The owner field is a special string that takes the
form:
inode_%lld_data
for inode data.
inode_%lld_data_bmbt
for inode data extent maps.
inode_%lld_attr
for inode extended attribute data.
inode_%lld_attr_bmbt
for inode extended attribute extent maps.
special_%u:%u
for other filesystem metadata.
-n num_extents
If this option is given, fsmap obtains the extent list
of the file in groups of num_extents extents. In the
absence of -n, fsmap queries the system for extents in
groups of 131,072 records.
-v Shows verbose information. When this flag is speci-
fied, additional AG specific information is appended
to each line in the following form:
agno (startagblock..endagblock) nblocks flags
A second -v option will print out the flags legend.
This option is not compatible with the -m flag.
OTHER COMMANDS
help [ command ]
Display a brief description of one or all commands.
print Display a list of all open files and memory mapped regions. The
current file and current mapping are distinguishable from any
others.
p See the print command.
quit Exit xfs_io.
q See the quit command.
log_writes -d device -m mark
Create a mark named mark in the dm-log-writes log specified by
device. This is intended to be equivalent to the shell command:
dmsetup message device 0 mark mark
lw See the log_writes command.
crc32cselftest
Test the internal crc32c implementation to make sure that it
computes results correctly.
SEE ALSO
mkfs.xfs(8), xfsctl(3), xfs_bmap(8), xfs_db(8), xfs(5), fdatasync(2),
fstat(2), fstatfs(2), fsync(2), ftruncate(2), futimens(3), mmap(2),
msync(2), open(2), pread(2), pwrite(2), readdir(3), dmsetup(8).
xfs_io(8)
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