IOCTL-XFS-SCRUB-METADATA(2)

NAME
ioctl_xfs_scrub_metadata - check XFS filesystem metadata

SYNOPSIS
#include <xfs/xfs_fs.h>

int ioctl(int dest_fd, XFS_IOC_SCRUB_METADATA, struct xfs_scrub_metadata *arg);

DESCRIPTION
This XFS ioctl asks the kernel driver to examine a piece of filesystem metadata for errors or suboptimal metadata. Examination includes running metadata verifiers, checking records for obviously incorrect or impossible values, and cross-referencing each record with any other available metadata in the filesystem. This ioctl can also try to repair or optimize metadata, though this may block normal filesystem operations for a long period of time. The type and location of the metadata to scrub is conveyed in a structure of the following form:

struct xfs_scrub_metadata {
	__u32 sm_type;
	__u32 sm_flags;
	__u64 sm_ino;
	__u32 sm_gen;
	__u32 sm_agno;
	__u64 sm_reserved[5];
};

The field sm_reserved must be zero.

The field sm_type indicates the type of metadata to check:

    XFS_SCRUB_TYPE_PROBE
        Probe the kernel to see if it is willing to try to check or repair this filesystem. sm_agno, sm_ino, and sm_gen must be zero.

    XFS_SCRUB_TYPE_SB
    XFS_SCRUB_TYPE_AGF
    XFS_SCRUB_TYPE_AGFL
    XFS_SCRUB_TYPE_AGI
        Examine a given allocation group's superblock, free space header, free block list, or inode header, respectively. Headers are checked for obviously incorrect values and cross-referenced against the allocation group's metadata btrees, if possible. The allocation group number must be given in sm_agno. sm_ino and sm_gen must be zero.

    XFS_SCRUB_TYPE_BNOBT
    XFS_SCRUB_TYPE_CNTBT
    XFS_SCRUB_TYPE_INOBT
    XFS_SCRUB_TYPE_FINOBT
    XFS_SCRUB_TYPE_RMAPBT
    XFS_SCRUB_TYPE_REFCNTBT
        Examine a given allocation group's two free space btrees, two inode btrees, reverse mapping btrees, or reference count btrees, respectively. Records are checked for obviously incorrect values and cross-referenced with other allocation group metadata records to ensure that there are no conflicts. The allocation group number must be given in sm_agno. sm_ino and sm_gen must be zero.

    XFS_SCRUB_TYPE_RGSUPER
        Examine a given realtime allocation group's superblock. The realtime allocation group number must be given in sm_agno. sm_ino and sm_gen must be zero.

    XFS_SCRUB_TYPE_INODE
        Examine a given inode record for obviously incorrect values and discrepancies with the rest of filesystem metadata. Parent pointers are checked for impossible inode values and are then followed up to the parent directory to ensure that the linkage is correct. The inode to examine may be specified either through sm_ino and sm_gen; if not specified, then the file described by dest_fd will be examined. sm_agno must be zero.

    XFS_SCRUB_TYPE_BMBTD
    XFS_SCRUB_TYPE_BMBTA
    XFS_SCRUB_TYPE_BMBTC
        Examine a given inode's data block map, extended attribute block map, or copy on write block map. Inode records are examined for obviously incorrect values and discrepancies with the three block map types. The block maps are checked for obviously wrong values and cross-referenced with the allocation group space extent metadata for discrepancies. The inode to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_XATTR
        Examine the extended attribute records and indices of a given inode for incorrect pointers and other signs of damage. The inode to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_DIR
        Examine the entries in a given directory for invalid data or dangling pointers. If the filesystem supports directory parent pointers, each entry will be checked to confirm that the child file has a matching parent pointer. The directory to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_PARENT
        For filesystems that support directory parent pointers, this scrubber examines all the parent pointers attached to a file and confirms that the parent directory has an entry matching the parent pointer. For filesystems that do not support directory parent pointers, this scrubber checks that a subdirectory's dotdot entry points to a directory with an entry that points back to the subdirectory. The inode to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_DIRTREE
        This scrubber looks for problems in the directory tree structure such as loops and directories accessible through more than one path. Problems are detected by walking parent pointers upwards towards the root. Loops are detected by comparing the parent directory at each step against the directories already examined. Directories with multiple paths are detected by counting the parent pointers attached to a directory. Non-directories do not have links pointing away from the directory tree root and can be skipped. The directory to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_SYMLINK
        Examine the target of a symbolic link for obvious pathname problems. The link to examine can be specified in the same manner as XFS_SCRUB_TYPE_INODE.

    XFS_SCRUB_TYPE_RTBITMAP
    XFS_SCRUB_TYPE_RTSUM
        Examine the realtime block bitmap and realtime summary inodes for corruption.

    XFS_SCRUB_TYPE_UQUOTA
    XFS_SCRUB_TYPE_GQUOTA
    XFS_SCRUB_TYPE_PQUOTA
        Examine all user, group, or project quota records for corruption.

    XFS_SCRUB_TYPE_FSCOUNTERS
        Examine all filesystem summary counters (free blocks, inode count, free inode count) for errors.

    XFS_SCRUB_TYPE_NLINKS
        Scan all inodes in the filesystem to verify each file's link count.

    XFS_SCRUB_TYPE_HEALTHY
        Mark everything healthy after a clean scrub run. This clears out all the indirect health problem markers that might remain in the system.

    XFS_SCRUB_TYPE_METAPATH
        Check that a metadata directory path actually points to the active metadata inode. Metadata inodes are usually cached for the duration of the mount, so this scrubber ensures that the same inode will still be reachable after an unmount and mount cycle. Discrepancies can happen if the directory or parent pointer scrubbers rebuild a metadata directory but lose a link in the process. The sm_ino field should be passed one of the following special values to communicate which path to check:

        XFS_SCRUB_METAPATH_RTDIR
            Realtime metadata file subdirectory.
        XFS_SCRUB_METAPATH_RTBITMAP
            Realtime bitmap file.
        XFS_SCRUB_METAPATH_RTSUMMARY
            Realtime summary file.
        XFS_SCRUB_METAPATH_QUOTADIR
            Quota metadata file subdirectory.
        XFS_SCRUB_METAPATH_USRQUOTA
            User quota file.
        XFS_SCRUB_METAPATH_GRPQUOTA
            Group quota file.
        XFS_SCRUB_METAPATH_PRJQUOTA
            Project quota file.

    The values of sm_agno and sm_gen must be zero.

The field sm_flags control the behavior of the scrub operation and provide more information about the outcome of the operation. If none of the XFS_SCRUB_OFLAG_* flags are set upon return, the metadata is clean.

    XFS_SCRUB_IFLAG_REPAIR
        If the caller sets this flag, the kernel driver will examine the metadata and try to fix all problems and to optimize metadata when possible. If no errors occur during the repair operation, the check is performed a second time to determine whether the repair succeeded. If errors occur, the call returns an error status immediately.

    XFS_SCRUB_OFLAG_CORRUPT
        The metadata was corrupt when the call returned. If XFS_SCRUB_IFLAG_REPAIR was specified, then an attempted repair failed to fix the problem. Unmount the filesystem and run xfs_repair to fix the filesystem.

    XFS_SCRUB_OFLAG_PREEN
        The metadata is ok, but some aspect of the metadata could be optimized to increase performance. Call again with XFS_SCRUB_IFLAG_REPAIR to optimize the metadata.

    XFS_SCRUB_OFLAG_XFAIL
        Filesystem errors were encountered when accessing other metadata to cross-reference the records attached to this metadata object.

    XFS_SCRUB_OFLAG_XCORRUPT
        Discrepancies were found when cross-referencing the records attached to this metadata object against all other available metadata in the system.

    XFS_SCRUB_OFLAG_INCOMPLETE
        The checker was unable to complete its check of all records.

    XFS_SCRUB_OFLAG_WARNING
        The checker encountered a metadata object with potentially problematic records. However, the records were not obviously corrupt.

For metadata checkers that operate on inodes or inode metadata, the fields sm_ino and sm_gen are the inode number and generation number of the inode to check. If the inode number is zero, the inode represented by dest_fd is used instead. If the generation number of the inode does not match sm_gen, the call will return an error code for the invalid argument. The sm_agno field must be zero.

For metadata checkers that operate on allocation group metadata, the field sm_agno indicates the allocation group in which to find the metadata. The sm_ino and sm_gen fields must be zero.

For metadata checkers that operate on filesystem-wide metadata, no further arguments are required. sm_agno, sm_ino, and sm_gen must all be zero.

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

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

EBUSY
    The filesystem object is busy; the operation will have to be tried again.

EFSCORRUPTED
    Severe filesystem corruption was detected and could not be repaired. Unmount the filesystem and run xfs_repair to fix the filesystem.

EINVAL
    One or more of the arguments specified is invalid.

ENOENT
    The specified metadata object does not exist. For example, this error code is returned for a XFS_SCRUB_TYPE_REFCNTBT request on a filesystem that does not support reflink.

ENOMEM
    There was not sufficient memory to perform the scrub or repair operation. Some operations (most notably reference count checking) require large amounts of memory.

ENOSPC
    There is not enough free disk space to attempt a repair.

ENOTRECOVERABLE
    Filesystem was mounted in norecovery mode and therefore has an unclean log. Neither scrub nor repair operations can be attempted with an unclean log.

ENOTTY
    Online scrubbing or repair were not enabled.

EOPNOTSUPP
    Repairs of the requested metadata object are not supported.

EROFS
    Filesystem is read-only and a repair was requested.

ESHUTDOWN
    Filesystem is shut down due to previous errors.

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

NOTES
These operations may block other filesystem operations for a long time. A calling process can stop the operation by being sent a fatal signal, but non-fatal signals are blocked.

SEE ALSO
ioctl(2) xfs_scrub(8) xfs_repair(8)