Provided by: xfsprogs_5.6.0-1ubuntu4_amd64 bug

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  interfaces 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 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.

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 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 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 incompatible 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  current  (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  permission
              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  number  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 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 [ -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 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 | -f N
              On  filesystems  that  support the copy_file_range(2) system call, copies data from
              the source file into the current open file.  The source must be specified either by
              path  (src_file)  or  as  another open file (-f).  If length is not specified, this
              command copies data from src_offset to the end of src_file  into  the  dst_file  at
              dst_offset.
                 -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 ] [ keyspec ]
              On  filesystems that support encryption, assign an encryption policy to the current
              file.  keyspec is a hex string which specifies the encryption key to use.   For  v1
              encryption  policies,  keyspec must be a 16-character hex string (8 bytes).  For v2
              policies, keyspec must be a 32-character hex string (16 bytes).  If unspecified, an
              all-zeroes value is 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
                     policy  version.   Defaults to 1 or 2 depending on the length of keyspec; or
                     to 1 if keyspec is unspecified.

       get_encpolicy [ -1 ] [ -t ]
              On filesystems that support  encryption,  display  the  encryption  policy  of  the
              current file.
                 -1  Use only the old ioctl to get the encryption policy.  This only works if the
                     file has a v1 encryption policy.
                 -t  Test whether v2 encryption  policies  are  supported.   Prints  "supported",
                     "unsupported", or an error message.

       add_enckey [ -d descriptor ] [ -k key_id ]
              On  filesystems  that  support  encryption, add an encryption key to the filesystem
              containing the currently open file.  By default, the raw key in  binary  (typically
              64 bytes long) is read from standard input.
                 -d descriptor
                     key  descriptor,  as a 16-character hex string (8 bytes).  If given, the key
                     will  be  available  for  use  by  v1  encryption  policies  that  use  this
                     descriptor.   Otherwise, the key is added as a v2 policy key, and on success
                     the resulting "key identifier" will be printed.
                 -k key_id
                     ID of kernel keyring key of type "fscrypt-provisioning".  If given, the  raw
                     key will be taken from here rather than from standard input.

       rm_enckey [ -a ] keyspec
              On  filesystems  that  support  encryption,  remove  an  encryption  key  from  the
              filesystem containing the currently open file.  keyspec is a hex string  specifying
              the  key  to  remove,  as  a  16-character  "key descriptor" or a 32-character "key
              identifier".
                 -a  Remove the key for all users who have added it, not just the  current  user.
                     This is a privileged operation.

       enckey_status keyspec
              On  filesystems  that  support encryption, display the status of an encryption key.
              keyspec is a hex string specifying the key for which to display the  status,  as  a
              16-character "key descriptor" or a 32-character "key identifier".

       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.

              The  current  inode  flag  letters  are  documented  below.   Please  refer  to the
              ioctl_xfs_fsgetxattr(2) documentation for more details about what they mean.

              r    realtime file (XFS_XFLAG_REALTIME)

              p    prealloc (XFS_XFLAG_PREALLOC)

              i    immutable (XFS_XFLAG_IMMUTABLE)

              a    append only (XFS_XFLAG_APPEND)

              s    synchronous file writes (XFS_XFLAG_SYNC)

              A    noatime (XFS_XFLAG_NOATIME)

              d    nodump (XFS_XFLAG_NODUMP)

              t    inherit realtime flag (XFS_XFLAG_RTINHERIT)"

              P    inherit project id (XFS_XFLAG_PROJINHERIT)

              n    no symlink creation (XFS_XFLAG_NOSYMLINKS)

              e    extent size hint (XFS_XFLAG_EXTSIZE)

              E    inherit extent size hint (XFS_XFLAG_EXTSZINHERIT)

              f    nodefrag (XFS_XFLAG_NODEFRAG)

              S    filestream allocator (XFS_XFLAG_FILESTREAM)

              x    direct access persistent memory (XFS_XFLAG_DAX)

              C    copy on write extent hint (XFS_XFLAG_COWEXTSIZE)

              X    has extended attributes (XFS_XFLAG_HASATTR)

       chattr [ -R | -D ] [ +/-riasAdtPneEfSxC ]
              Change extended inode flags on the currently open file. The -R and -D options  have
              the same meaning as above.

              See the lsattr command above for the list of inode flag letters.

       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 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.]

       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 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).  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  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 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  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.

FILESYSTEM COMMANDS

       bulkstat [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s startino ] [ -v version"]
              Display raw stat information about a bunch of inodes in an XFS filesystem.  Options
              are as follows:
                 -a agno
                        Display  only results from the given allocation group.  If not specified,
                        all results returned will be displayed.
                 -d     Print debugging information about call results.
                 -e endino
                        Stop displaying records when this inode number is reached.   Defaults  to
                        stopping when the system call stops returning results.
                 -n batchsize
                        Retrieve at most this many records per call.  Defaults to 4,096.
                 -s startino
                        Display  inode  allocation records starting with this inode.  Defaults to
                        the first inode in the filesystem.  If the given inode is not  allocated,
                        results will begin with the next allocated inode in the filesystem.
                 -v version
                        Use  a  particular  version of the kernel interface.  Currently supported
                        versions are 1 and 5.

       bulkstat_single [ -d ] [ -v version ] [ inum... | special... ]
              Display raw stat information about individual inodes in an XFS filesystem.  The  -d
              and  -v  options  are  the  same  as the bulkstat command.  Arguments must be inode
              numbers or any of the special values:
                 root   Display information about the root directory inode.

       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.

       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.

       inumbers [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s startino ] [ -v version ]
              Prints allocation information about groups of inodes in an XFS filesystem.  Callers
              can  use this information to figure out which inodes are allocated.  Options are as
              follows:
                 -a agno
                        Display only results from the given allocation group.  If not  specified,
                        all results returned will be displayed.
                 -d     Print debugging information about call results.
                 -e endino
                        Stop  displaying  records when this inode number is reached.  Defaults to
                        stopping when the system call stops returning results.
                 -n batchsize
                        Retrieve at most this many records per call.  Defaults to 4,096.
                 -s startino
                        Display inode allocation records starting with this inode.   Defaults  to
                        the  first inode in the filesystem.  If the given inode is not allocated,
                        results will begin with the next allocated inode in the filesystem.
                 -v version
                        Use a particular version of the kernel  interface.   Currently  supported
                        versions are 1 and 5.

       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
              generation 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 current  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 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.

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)