Manpages - ioctl_xfs_getbmapx.2

ioctl_xfs_getbmapx - query extent information for an open file

#include <xfs/xfs_fs.h>

int ioctl(int */fd/, XFS_IOC_GETBMAP, struct getbmap */arg/);*
int ioctl(int */fd/, XFS_IOC_GETBMAPA, struct getbmap */arg/);*
int ioctl(int */fd/, XFS_IOC_GETBMAPX, struct getbmapx */arg/);*

Get the block map for a segment of a file in an XFS file system. The mapping information is conveyed via an array of structures of the following form:

  struct getbmap {
  	__s64   bmv_offset;
  	__s64   bmv_block;
  	__s64   bmv_length;
  	__s32   bmv_count;
  	__s32   bmv_entries;
  };

The XFS_IOC_GETBMAPX ioctl uses a larger version of that structure:

  struct getbmapx {
  	__s64   bmv_offset;
  	__s64   bmv_block;
  	__s64   bmv_length;
  	__s32   bmv_count;
  	__s32   bmv_entries;
  	__s32   bmv_iflags;
  	__s32   bmv_oflags;
  	__s32   bmv_unused1;
  	__s32   bmv_unused2;
  };

All sizes and offsets in the structure are in units of 512 bytes.

The first structure in the array is a header and the remaining structures in the array contain block map information on return. The header controls iterative calls to the command and should be filled out as follows:

bmv_offset

The file offset of the area of interest in the file.

bmv_length

The length of the area of interest in the file. If this value is set to -1, the length of the interesting area is the rest of the file.

bmv_count

The number of elements in the array, including this header. The minimum value is 2.

bmv_entries

The number of entries actually filled in by the call. This does not need to be filled out before the call. This value may be zero if no extents were found in the requested range, or if iterated calls have reached the end of the requested range.

bmv_iflags

For the XFS_IOC_GETBMAPX function, this is a bitmask containing a combination of the following flags:

BMV_IF_ATTRFORK

Return information about the extended attribute fork.

BMV_IF_PREALLOC

Return information about unwritten pre-allocated segments.

BMV_IF_DELALLOC

Return information about delayed allocation reservation segments.

BMV_IF_NO_HOLES

Do not return information about holes.

The other bmv_* fields in the header are ignored.

On successful return from a call, the offset and length values in the header are updated so that the command can be reused to obtain more information. The remaining elements of the array will be filled out by the call as follows:

bmv_offset

File offset of segment.

bmv_block

Physical starting block of segment. If this is -1, then the segment is a hole.

bmv_length

Length of segment.

bmv_oflags

The XFS_IOC_GETBMAPX function will fill this field with a combination of the following flags:

BMV_OF_PREALLOC

The segment is an unwritten pre-allocation.

BMV_OF_DELALLOC

The segment is a delayed allocation reservation.

BMV_OF_LAST

This segment is the last in the file.

BMV_OF_SHARED

This segment shares blocks with other files.

The other bmv_* fields are unused in the array of output records.

The XFS_IOC_GETBMAPA command is identical to XFS_IOC_GETBMAP except that information about the attribute fork of the file is returned.

On error, -1 is returned, and errno is set to indicate the error.

Error codes can be one of, but are not limited to, the following:

EFAULT

The kernel was not able to copy into the userspace buffer.

EFSBADCRC

Metadata checksum validation failed while performing the query.

EFSCORRUPTED

Metadata corruption was encountered while performing the query.

EINVAL

One of the arguments was not valid.

EIO

An I/O error was encountered while performing the query.

ENOMEM

There was insufficient memory to perform the query.

This API is specific to XFS filesystem on the Linux kernel.

*ioctl*(2)