IOCTL-XFS-SCRUB-METADATA

Section: System Calls (2)
Updated: 2017-12-01
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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_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

XFS_SCRUB_TYPE_PARENT: Examine a given inode's data block map, extended attribute block map, copy on write block map, or parent inode pointer. 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. 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.

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.