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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONCEPTS | FILE I/O COMMANDS | MEMORY MAPPED I/O COMMANDS | OTHER COMMANDS | SEE ALSO | COLOPHON |
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xfs_io(8) System Manager's Manual xfs_io(8)
xfs_io - debug the I/O path of an XFS filesystem
xfs_io [ -adfimrRstxT ] [ -c cmd ] ... [ -C cmd ] ... [ -p prog ] [
file ]
xfs_io -V
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
interfaces for manipulating files, but also cover all of the XFS
extensions (such as space preallocation, additional inode flags,
etc).
xfs_io commands may be run interactively (the default) or as
arguments on the command line. Interactive mode always runs commands
on the current 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
privileges.
-V Prints the version number and exits.
The other open(2) options described below are also available from the
command line.
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
preallocation, 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 [ N ]
Display a list of all open files and (optionally) switch to an
alternate current open file.
open [[ -acdfrstRT ] 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.
o See the open command.
close Closes the current open file, marking the next open file as
current (if one exists).
c See the close command.
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 ] [ -dwNOW ] [ -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.
-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
number of blocksize length iovecs. The number of iovecs
is set by the vectors parameter.
w See the pwrite command.
bmap [ -acdelpv ] [ -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 ]
Prints the block mapping for the current open file using the
fiemap ioctl. Options behave as described in the xfs_bmap(8)
manual page.
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
filesystem metadata, as well as any regions that are unused.
Each line of the listings takes the following form:
extent: major:minor [startblock..endblock]: owner
startoffset..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 specified, 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
specified, 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.
extsize [ -R | -D ] [ value ]
Display and/or modify the preferred 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 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
system 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_RANDOM), which sets readahead to zero.
-s expect access to data in sequential order
(POSIX_FADV_SEQUENTIAL), which doubles the default
readahead on the file.
-w advises the specified data will be needed again
(POSIX_FADV_WILLNEED[*]) which forces the maximum
readahead.
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
eliminates 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
fallocate(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 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.
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
ftruncate(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
target, 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
readdir(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
specified offset.
-d Display the data segment starting at the specified
offset.
-h Display the hole segment starting at the specified
offset.
-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_offset, 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.
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.
mmap [ N | [[ -rwx ] [-s size ] offset length ]]
With no arguments, mmap shows the current mappings. Specifying
a single numeric argument N sets the current mapping. If two
arguments 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). -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 helpful 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 setted 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 backwards through the mapping if the -r
option in specified. The two verbose modes differ only in the
relative offsets they display, 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
specified, 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
mapping. 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_SEQUENTIAL), which doubles the default
readahead on the file.
-w advises the specified pages will be needed again
(POSIX_MADV_WILLNEED[*]) which forces the maximum
readahead.
mincore
Dumps a list of pages or ranges of pages that are currently in
core, for the current memory mapping.
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.
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.
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
available in expert mode and requires privileges.
flink path
Link the currently open file descriptor into the filesystem
namespace.
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 shutdown (with or without flushing the
log). Only available in expert mode and requires privileges.
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.
statfs Selected statistics from statfs(2) and the XFS_IOC_FSGEOMETRY
system call on the filesystem where the current file resides.
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
pathnames 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.]
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.
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.
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).
This page is part of the xfsprogs (utilities for XFS filesystems)
project. Information about the project can be found at
⟨http://xfs.org/⟩. If you have a bug report for this manual page, see
⟨http://oss.sgi.com/bugzilla/buglist.cgi?product=XFS⟩. This page was
obtained from the project's upstream Git repository
⟨git://oss.sgi.com/xfs/cmds/xfsprogs⟩ on 2018-02-02. (At that time,
the date of the most recent commit that was found in the repository
was 2017-11-27.) If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-to-
date source for the page, or you have corrections or improvements to
the information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
xfs_io(8)
Pages that refer to this page: xfs_fsr(8)
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