.TH xfs_io 8
.SH NAME
xfs_io \- debug the I/O path of an XFS filesystem
.SH SYNOPSIS
.B xfs_io
[
.B \-adfimrRstxT
] [
.B \-c
.I cmd
] ... [
.B \-C
.I cmd
] ... [
.B \-p
.I prog
]
.I [ file ]
.br
.B xfs_io \-V
.SH DESCRIPTION
.B xfs_io
is a debugging tool like
.BR 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).
.SH OPTIONS
.B 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.
.TP 1.0i
.BI \-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
.B \-c
arguments may be given and may be interleaved on the command line in any order
with
.B \-C
commands.
.TP
.BI \-C " cmd"
Run the specified command only on the current open file. 
Multiple
.B \-C
arguments may be given and may be interleaved on the command line in any order
with
.B \-c
commands.
.TP
.BI \-p " prog"
Set the program name for prompts and some error messages,
the default value is
.BR xfs_io .
.TP
.B \-f
Create
.I file
if it does not already exist.
.TP
.B \-r
Open
.I file
read-only, initially. This is required if
.I file
is immutable or append-only.
.TP
.B \-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.
.TP
.B \-x
Expert mode. Dangerous commands are only available in this mode.
These commands also tend to require additional privileges.
.TP
.B \-V
Prints the version number and exits.
.PP
The other
.BR open (2)
options described below are also available from the command line.
.SH CONCEPTS
.B 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.
.PP
.B 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.
.PP
The second set of commands exist for manipulating memory mapped regions
of a file - mapping, accessing, storing, unmapping, flushing, etc.
.PP
The remaining commands are for the navigation and display of data
structures relating to the open files, mappings, and the filesystems
where they reside.
.PP
Many commands have extensive online help. Use the
.B help
command for more details on any command.
.SH FILE I/O COMMANDS
.TP
.BI "file [ " N " ]"
Display a list of all open files and (optionally) switch to an alternate
current open file.
.TP
.BI "open [[ \-acdfrstRT ] " path " ]"
Closes the current file, and opens the file specified by
.I path
instead. Without any arguments, displays statistics about the current
file \- see the
.B stat
command.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-a
opens append-only (O_APPEND).
.TP
.B \-d
opens for direct I/O (O_DIRECT).
.TP
.B \-f
creates the file if it doesn't already exist (O_CREAT).
.TP
.B \-r
opens read-only (O_RDONLY).
.TP
.B \-s
opens for synchronous I/O (O_SYNC).
.TP
.B \-t
truncates on open (O_TRUNC).
.TP
.B \-n
opens in non-blocking mode if possible (O_NONBLOCK).
.TP
.B \-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
.B \-r
option.
.TP
.B \-R
marks the file as a realtime XFS file after
opening it, if it is not already marked as such.
.PD
.RE
.TP
.B o
See the
.B open
command.
.TP
.B close
Closes the current open file, marking the next open file as current
(if one exists).
.TP
.B c
See the
.B close
command.
.TP
.BI "pread [ \-b " bsize " ] [ \-v ] [ \-FBR [ \-Z " seed " ] ] [ \-V " vectors " ] " "offset length"
Reads a range of bytes in a specified blocksize from the given
.IR offset .
.RS 1.0i
.PD 0
.TP 0.4i
.B \-b
can be used to set the blocksize into which the
.BR read (2)
requests will be split. The default blocksize is 4096 bytes.
.TP
.B \-v
dump the contents of the buffer after reading,
by default only the count of bytes actually read is dumped.
.TP
.B \-F
read the buffers in a forwards sequential direction.
.TP
.B \-B
read the buffers in a reserve sequential direction.
.TP
.B \-R
read the buffers in the give range in a random order.
.TP
.B \-Z seed
specify the random number seed used for random reads.
.TP
.B \-V vectors
Use the vectored IO read syscall
.BR preadv (2)
with a number of blocksize length iovecs. The number of iovecs is set by the
.I vectors
parameter.
.PD
.RE
.TP
.B r
See the
.B pread
command.
.TP
.BI "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
.IR offset .
The bytes written can be either a set pattern or read in from another
file before writing.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-i
allows an input
.I file
to be specified as the source of the data to be written.
.TP
.B \-d
causes direct I/O, rather than the usual buffered
I/O, to be used when reading the input file.
.TP
.B \-w
call
.BR fdatasync (2)
once all writes are complete (included in timing results)
.TP
.B \-N
Perform the
.BR pwritev2 (2)
call with
.IR RWF_NOWAIT .
.TP
.B \-D
Perform the
.BR pwritev2 (2)
call with
.IR RWF_DSYNC .
.TP
.B \-O
perform pwrite once and return the (maybe partial) bytes written.
.TP
.B \-W
call
.BR fsync (2)
once all writes are complete (included in timing results)
.TP
.B \-s
specifies the number of bytes to
.I skip
from the start of the input file before starting to read.
.TP
.B \-b
used to set the blocksize into which the
.BR write (2)
requests will be split. The default blocksize is 4096 bytes.
.TP
.B \-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.
.TP
.B \-F
write the buffers in a forwards sequential direction.
.TP
.B \-B
write the buffers in a reserve sequential direction.
.TP
.B \-R
write the buffers in the give range in a random order.
.TP
.B \-Z seed
specify the random number seed used for random write
.TP
.B \-V vectors
Use the vectored IO write syscall
.BR pwritev (2)
with a number of blocksize length iovecs. The number of iovecs is set by the
.I vectors
parameter.
.RE
.PD
.TP
.B w
See the
.B pwrite
command.
.TP
.BI "bmap [ \-acdelpv ] [ \-n " nx " ]"
Prints the block mapping for the current open file. Refer to the
.BR xfs_bmap (8)
manual page for complete documentation.
.TP
.BI "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
.BR xfs_bmap (8)
manual page.
.PP
.RS
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
.B fiemap
command will print them in their entirety.  If the requested range starts
or ends in a hole,
.B fiemap
will print the hole, truncated to the requested range.
.RE
.TP
.BI "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:
.PP
.RS
.IR extent ": " major ":" minor " [" startblock .. endblock "]: " owner " " startoffset .. endoffset " " length
.PP
Static filesystem metadata, allocation group metadata, btrees,
journalling logs, and free space are marked by replacing the
.IR 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
.I start
and
.I 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
.BR "-d" ", " "-l" ", or " "-r"
must also be set.
.RE
.RS 1.0i
.PD 0
.TP
.BI \-d
Display only extents from the data device.
This option only applies for XFS filesystems.
.TP
.BI \-l
Display only extents from the external log device.
This option only applies to XFS filesystems.
.TP
.BI \-r
Display only extents from the realtime device.
This option only applies to XFS filesystems.
.TP
.BI \-m
Display results in a machine readable format (CSV).
This option is not compatible with the
.B \-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:

.RS 1.0i
.PD 0
.TP 0.4i
.I inode_%lld_data
for inode data.
.TP
.I inode_%lld_data_bmbt
for inode data extent maps.
.TP
.I inode_%lld_attr
for inode extended attribute data.
.TP
.I inode_%lld_attr_bmbt
for inode extended attribute extent maps.
.TP
.I special_%u:%u
for other filesystem metadata.
.PD
.RE

.TP
.BI \-n " num_extents"
If this option is given,
.B fsmap
obtains the extent list of the file in groups of
.I num_extents
extents.
In the absence of
.BR "-n" ", " "fsmap"
queries the system for extents in groups of 131,072 records.
.TP
.B \-v
Shows verbose information.
When this flag is specified, additional AG specific information is
appended to each line in the following form:
.IP
.RS 1.2i
.IR agno " (" startagblock .. endagblock ") " nblocks " " flags
.RE
.IP
A second
.B \-v
option will print out the
.I flags
legend.
This option is not compatible with the
.B \-m
flag.
.RE
.PD
.TP
.BI "extsize [ \-R | \-D ] [ " value " ]"
Display and/or modify the preferred extent size used when allocating
space for the currently open file. If the
.B \-R
option is specified, a recursive descent is performed
for all directory entries below the currently open file
.RB ( \-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
.I 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.
.TP
.BI "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
.B \-R
option is specified, a recursive descent is performed
for all directory entries below the currently open file
.RB ( \-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
.I 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.
.TP
.BI "allocsp " size " 0"
Sets the size of the file to
.I size
and zeroes any additional space allocated using the
XFS_IOC_ALLOCSP/XFS_IOC_FREESP system call described in the
.BR xfsctl (3)
manual page.
.B allocsp
and
.B freesp
do exactly the same thing.
.TP
.BI "freesp " size " 0"
See the
.B allocsp
command.
.TP
.BI "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).
.RS 1.0i
.PD 0
.TP 0.4i
.B \-d
the data will not be accessed again in the near future (POSIX_FADV_DONTNEED[*]).
.TP
.B \-n
data will be accessed once and not be reused (POSIX_FADV_NOREUSE[*]).
.TP
.B \-r
expect access to data in random order (POSIX_FADV_RANDOM), which sets readahead to zero.
.TP
.B \-s
expect access to data in sequential order (POSIX_FADV_SEQUENTIAL),
which doubles the default readahead on the file.
.TP
.B \-w
advises the specified data will be needed again (POSIX_FADV_WILLNEED[*])
which forces the maximum readahead.
.RE
.PD
.TP
.B fdatasync
Calls
.BR fdatasync (2)
to flush the file's in-core data to disk.
.TP
.B fsync
Calls
.BR fsync (2)
to flush all in-core file state to disk.
.TP
.B s
See the
.B fsync
command.
.TP
.BI "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.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-a
wait for IO in the given range to finish after writing
(SYNC_FILE_RANGE_WAIT_AFTER).
.TP
.B \-b
wait for IO in the given range to finish before writing
(SYNC_FILE_RANGE_WAIT_BEFORE).
.TP
.B \-w
start writeback of dirty data in the given range (SYNC_FILE_RANGE_WRITE).
.RE
.PD
.TP
.B sync
Calls
.BR sync (2)
to flush all filesystems' in-core data to disk.
.TP
.B syncfs
Calls
.BR syncfs (2)
to flush this filesystem's in-core data to disk.
.TP
.BI resvsp " offset length"
Allocates reserved, unwritten space for part of a file using the
XFS_IOC_RESVSP system call described in the
.BR xfsctl (3)
manual page.
.TP
.BI unresvsp " offset length"
Frees reserved space for part of a file using the XFS_IOC_UNRESVSP
system call described in the
.BR xfsctl (3)
manual page.
.TP
.BI "falloc [ \-k ]" " offset length"
Allocates reserved, unwritten space for part of a file using the
fallocate routine as described in the
.BR fallocate (2)
manual page.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-k
will set the FALLOC_FL_KEEP_SIZE flag as described in
.BR fallocate (2).
.PD
.RE
.TP
.BI fcollapse " offset length"
Call fallocate with FALLOC_FL_COLLAPSE_RANGE flag as described in the
.BR fallocate (2)
manual page to de-allocates blocks and eliminates the hole created in this process
by shifting data blocks into the hole.
.TP
.BI finsert " offset length"
Call fallocate with FALLOC_FL_INSERT_RANGE flag as described in the
.BR fallocate (2)
manual page to create the hole by shifting data blocks.
.TP
.BI fpunch " offset length"
Punches (de-allocates) blocks in the file by calling fallocate with 
the FALLOC_FL_PUNCH_HOLE flag as described in the
.BR fallocate (2)
manual page.
.TP
.BI funshare " offset length"
Call fallocate with FALLOC_FL_UNSHARE_RANGE flag as described in the
.BR fallocate (2)
manual page to unshare all shared blocks within the range.
.TP
.BI fzero " offset length"
Call fallocate with FALLOC_FL_ZERO_RANGE flag as described in the
.BR fallocate (2)
manual page to allocate and zero blocks within the range.
.TP
.BI zero " offset length"
Call xfsctl with
.B XFS_IOC_ZERO_RANGE
as described in the
.BR xfsctl (3)
manual page to allocate and zero blocks within the range.
.TP
.BI truncate " offset"
Truncates the current file at the given offset using
.BR ftruncate (2).
.TP
.BI "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
.RB ( \-f )
or by path
.RB ( \-i ).
.TP
.BI "readdir [ -v ] [ -o " offset " ] [ -l " length " ] "
Read a range of directory entries from a given offset of a directory.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-v
verbose mode - dump dirent content as defined in
.BR readdir (3)
.TP
.B \-o
specify starting
.I offset
.TP
.B \-l
specify total
.I length
to read (in bytes)
.RE
.PD
.TP
.BI "seek  \-a | \-d | \-h [ \-r ] [ \-s ] offset"
On platforms that support the
.BR lseek (2)
.B SEEK_DATA
and
.B SEEK_HOLE
options, display the offsets of the specified segments.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-a
Display both
.B data
and
.B hole
segments starting at the specified
.B offset.
.TP
.B \-d
Display the
.B data
segment starting at the specified
.B offset.
.TP
.B \-h
Display the
.B hole
segment starting at the specified
.B offset.
.TP
.B \-r
Recursively display all the specified segments starting at the specified
.B offset.
.TP
.B \-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.
.RE
.PD
.TP
.BI "reflink  [ \-C ] [ \-q ] src_file [src_offset dst_offset length]"
On filesystems that support the
.B FICLONERANGE
or
.B BTRFS_IOC_CLONE_RANGE
ioctls, map
.I length
bytes at offset
.I dst_offset
in the open file to the same physical blocks that are mapped at offset
.I src_offset
in the file
.I 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.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-C
Print timing statistics in a condensed format.
.TP
.B \-q
Do not print timing statistics at all.
.RE
.PD
.TP
.BI "dedupe  [ \-C ] [ \-q ] src_file src_offset dst_offset length"
On filesystems that support the
.B FIDEDUPERANGE
or
.B BTRFS_IOC_FILE_EXTENT_SAME
ioctls, map
.I length
bytes at offset
.I dst_offset
in the open file to the same physical blocks that are mapped at offset
.I src_offset
in the file
.I 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.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-C
Print timing statistics in a condensed format.
.TP
.B \-q
Do not print timing statistics at all.
.RE
.PD
.TP
.BI "copy_range [ -s " src_offset " ] [ -d " dst_offset " ] [ -l " length " ] src_file"
On filesystems that support the
.BR copy_file_range (2)
system call, copies data from the
.I src_file
into the open file.  If
.IR src_offset ,
.IR dst_offset ,
and
.I length
are omitted the contents of src_file will be copied to the beginning of the
open file, overwriting any data already there.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-s
Copy data from
.I src_file
beginning from
.IR src_offset .
.TP
.B \-d
Copy data into the open file beginning at
.IR dst_offset .
.TP
.B \-l
Copy up to
.I length
bytes of data.
.RE
.PD
.TP
.BI 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.
.TP
.BI 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)).

.SH MEMORY MAPPED I/O COMMANDS
.TP
.BI "mmap [ " N " | [[ \-rwxS ] [\-s " size " ] " "offset length " ]]
With no arguments,
.B mmap
shows the current mappings. Specifying a single numeric argument
.I N
sets the current mapping. If two arguments are specified (a range specified by
.I offset
and
.IR length ),
a new mapping is created spanning the range, and the protection mode can
be given as a combination of PROT_READ
.RB ( \-r ),
PROT_WRITE
.RB ( \-w ),
and PROT_EXEC
.RB ( \-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
.B -S
is given.
.BI \-s " size"
is used to do a mmap(size) && munmap(size) operation at first, try to reserve some
extendible free memory space, if
.I size
is bigger than
.I length
parameter. But there's not guarantee that the memory after
.I length
( up to
.I size
) will stay free.
.B 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.
.TP
.B mm
See the
.B mmap
command.
.TP
.BI "mremap [ \-f <new_address> ] [ \-m ] " new_length
Changes the current mapping size to
.IR new_length .
Whether the mapping may be moved is controlled by the flags passed;
MREMAP_FIXED
.RB ( \-f ),
or MREMAP_MAYMOVE
.RB ( \-m ).
.IR new_length
specifies a page-aligned address to which the mapping must be moved. It
can be set to 139946004389888, 4096k or 1g etc.
.TP
.B mrm
See the
.B mremap
command.
.TP
.B munmap
Unmaps the current memory mapping.
.TP
.B mu
See the
.B munmap
command.
.TP
.BI "mread [ \-f | \-v ] [ \-r ] [" " offset length " ]
Accesses a segment of the current memory mapping, optionally dumping it to
the standard output stream (with
.B \-v
or
.B \-f
option) for inspection. The accesses are performed sequentially from the start
.I offset
by default, but can also be done from the end backwards through the
mapping if the
.B \-r
option in specified.
The two verbose modes differ only in the relative offsets they display, the
.B \-f
option is relative to file start, whereas
.B \-v
shows offsets relative to the start of the mapping.
.TP
.B mr
See the
.B mread
command.
.TP
.BI "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
.B \-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
.B \-r
option in specified.
.TP
.B mw
See the
.B mwrite
command.
.TP
.BI "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
.RB ( \-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
.RB ( \-s)
or asynchronously
.RB ( \-a ).
.TP
.B ms
See the
.B msync
command.
.TP
.BI "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).
.RS 1.0i
.PD 0
.TP 0.4i
.B \-d
the pages will not be needed (POSIX_MADV_DONTNEED[*]).
.TP
.B \-r
expect random page references (POSIX_MADV_RANDOM), which sets readahead to zero.
.TP
.B \-s
expect sequential page references (POSIX_MADV_SEQUENTIAL),
which doubles the default readahead on the file.
.TP
.B \-w
advises the specified pages will be needed again (POSIX_MADV_WILLNEED[*])
which forces the maximum readahead.
.RE
.PD
.TP
.B mincore
Dumps a list of pages or ranges of pages that are currently in core,
for the current memory mapping.

.SH OTHER COMMANDS
.TP
.BR "help [ " command " ]"
Display a brief description of one or all commands.
.TP
.B print
Display a list of all open files and memory mapped regions.
The current file and current mapping are distinguishable from
any others.
.TP
.B p
See the
.B print
command.
.TP
.B quit
Exit
.BR xfs_io .
.TP
.B q
See the
.B quit
command.
.TP
.BR lsattr " [ " \-R " | " \-D " | " \-a " | " \-v " ]"
List extended inode flags on the currently open file. If the
.B \-R
option is specified, a recursive descent is performed
for all directory entries below the currently open file
.RB ( \-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.
.TP
.BR chattr " [ " \-R " | " \-D " ] [ " + / \-riasAdtPneEfSxC " ]"
Change extended inode flags on the currently open file. The
.B \-R
and
.B \-D
options have the same meaning as above. The mapping between each
letter and the inode flags (refer to
.BR xfsctl (3)
for the full list) is available via the
.B help
command.
.TP
.B freeze
Suspend all write I/O requests to the filesystem of the current file.
Only available in expert mode and requires privileges.
.TP
.B thaw
Undo the effects of a filesystem freeze operation.
Only available in expert mode and requires privileges.
.TP
.BI "flink " path
Link the currently open file descriptor into the filesystem namespace.
.TP
.BI "inject [ " tag " ]"
Inject errors into a filesystem to observe filesystem behavior at
specific points under adverse conditions. Without the
.I tag
argument, displays the list of error tags available.
Only available in expert mode and requires privileges.
.TP
.BI "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.
.TP
.BR shutdown " [ " \-f " ]"
Force the filesystem to shutdown (with or without flushing the log).
Only available in expert mode and requires privileges.
.TP
.BR stat " [ " \-v "|" \-r " ]"
Selected statistics from
.BR stat (2)
and the XFS_IOC_GETXATTR system call on the current file. If the
.B \-v
option is specified, the atime (last access), mtime
(last modify), and ctime (last change) timestamps are also displayed.  The
.B \-r
option dumps raw fields from the stat structure.
.TP
.BI "statx [ \-v|\-r ][ \-m " basic " | \-m " all " | -m " <mask> " ][ \-FD ]"
Selected statistics from
.BR stat (2)
and the XFS_IOC_GETXATTR system call on the current file.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-v
Show timestamps.
.TP
.B \-r
Dump raw statx structure values.
.TP
.B \-m basic
Set the field mask for the statx call to STATX_BASIC_STATS.
.TP
.B \-m all
Set the the field mask for the statx call to STATX_ALL (default).
.TP
.B \-m <mask>
Specify a numeric field mask for the statx call.
.TP
.B \-F
Force the attributes to be synced with the server.
.TP
.B \-D
Don't sync attributes with the server.
.PD
.RE
.TP
.B statfs
Selected statistics from
.BR statfs (2)
and the XFS_IOC_FSGEOMETRY
system call on the filesystem where the current file resides.
.TP
.BR chproj " [ " \-R | \-D " ]"
Modifies the project identifier associated with the current path. The 
.B \-R
option will recursively descend if the current path is a directory. The 
.B \-D
option will also recursively descend, only setting modifying projects 
on subdirectories.  See the
.BR xfs_quota (8)
manual page for more information about project identifiers.
.TP
.BR lsproj " [ " \-R | \-D " ]"
Displays the project identifier associated with the current path. The 
.B \-R
and
.B \-D
options behave as described above, in
.B chproj.
.TP
.BR 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.
.RS 1.0i
.PD 0
.TP 0.4i
.B \-p
the output is similar to the default output except pathnames up to
the mount-point are printed out instead of the component name.
.TP
.B \-c
the file's filesystem will check all the parent attributes for consistency.
.TP
.B \-v
verbose output will be printed.
.RE
.IP
.B [NOTE: Not currently operational on Linux.]
.RE
.PD
.TP
.BI "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
.I number
as an argument, the command will return the same inode
.I number
if it is in use, or 0 if not. With
.BI \-n " number"
, the next used inode number after this
.I number
will be returned, or zero if the supplied inode number is the highest one
in use. With
.B \-v
the command will also report the number of bits (32 or 64) used by the
inode
.I number
printed in the result; if no inode
.I number
was specified on the command line, the maximum possible inode number in
the system will be printed along with its size.
.PD
.TP
.BI "set_encpolicy [ \-c " mode " ] [ \-n " mode " ] [ \-f " flags " ] [ \-v " version " ] [ " keydesc " ]"
On filesystems that support encryption, assign an encryption policy to the
current file.
.I 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.
.RS 1.0i
.PD 0
.TP 0.4i
.BI \-c " mode"
contents encryption mode (e.g. AES-256-XTS)
.TP
.BI \-n " mode"
filenames encryption mode (e.g. AES-256-CTS)
.TP
.BI \-f " flags"
policy flags (numeric)
.TP
.BI \-v " version"
version of policy structure (numeric)
.RE
.PD
.TP
.BR get_encpolicy
On filesystems that support encryption, display the encryption policy of the
current file.
.TP
.BI "scrub " type " [ " agnumber " | " "ino" " " "gen" " ]"
Scrub internal XFS filesystem metadata.  The
.BI 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.
.RE
.PD
.TP
.BI "log_writes \-d " device " \-m "  mark
Create a mark named
.I mark
in the dm-log-writes log specified by
.I device.
This is intended to be equivalent to the shell command:

.B dmsetup message
.I device
.B 0 mark
.I mark
.PD
.RE
.TP
.B lw
See the
.B log_writes
command.
.SH SEE ALSO
.BR mkfs.xfs (8),
.BR xfsctl (3),
.BR xfs_bmap (8),
.BR xfs_db (8),
.BR xfs (5),
.BR fdatasync (2),
.BR fstat (2),
.BR fstatfs (2),
.BR fsync (2),
.BR ftruncate (2),
.BR futimens (3),
.BR mmap (2),
.BR msync (2),
.BR open (2),
.BR pread (2),
.BR pwrite (2),
.BR readdir (3),
.BR dmsetup (8).