^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) Fiemap Ioctl
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) The fiemap ioctl is an efficient method for userspace to get file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) extent mappings. Instead of block-by-block mapping (such as bmap), fiemap
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) returns a list of extents.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) Request Basics
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) --------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) A fiemap request is encoded within struct fiemap::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) struct fiemap {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) __u64 fm_start; /* logical offset (inclusive) at
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) * which to start mapping (in) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) __u64 fm_length; /* logical length of mapping which
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) * userspace cares about (in) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) __u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) __u32 fm_mapped_extents; /* number of extents that were
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) * mapped (out) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) __u32 fm_extent_count; /* size of fm_extents array (in) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) __u32 fm_reserved;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) fm_start, and fm_length specify the logical range within the file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) which the process would like mappings for. Extents returned mirror
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) those on disk - that is, the logical offset of the 1st returned extent
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) may start before fm_start, and the range covered by the last returned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) extent may end after fm_length. All offsets and lengths are in bytes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) Certain flags to modify the way in which mappings are looked up can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) set in fm_flags. If the kernel doesn't understand some particular
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) flags, it will return EBADR and the contents of fm_flags will contain
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) the set of flags which caused the error. If the kernel is compatible
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) with all flags passed, the contents of fm_flags will be unmodified.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) It is up to userspace to determine whether rejection of a particular
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) flag is fatal to its operation. This scheme is intended to allow the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) fiemap interface to grow in the future but without losing
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) compatibility with old software.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) fm_extent_count specifies the number of elements in the fm_extents[] array
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) that can be used to return extents. If fm_extent_count is zero, then the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) fm_extents[] array is ignored (no extents will be returned), and the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) fm_mapped_extents count will hold the number of extents needed in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) fm_extents[] to hold the file's current mapping. Note that there is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) nothing to prevent the file from changing between calls to FIEMAP.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) The following flags can be set in fm_flags:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) FIEMAP_FLAG_SYNC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) If this flag is set, the kernel will sync the file before mapping extents.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) FIEMAP_FLAG_XATTR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) If this flag is set, the extents returned will describe the inodes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) extended attribute lookup tree, instead of its data tree.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) Extent Mapping
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) --------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) Extent information is returned within the embedded fm_extents array
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) which userspace must allocate along with the fiemap structure. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) number of elements in the fiemap_extents[] array should be passed via
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) fm_extent_count. The number of extents mapped by kernel will be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) returned via fm_mapped_extents. If the number of fiemap_extents
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) allocated is less than would be required to map the requested range,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) the maximum number of extents that can be mapped in the fm_extent[]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) array will be returned and fm_mapped_extents will be equal to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) fm_extent_count. In that case, the last extent in the array will not
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) complete the requested range and will not have the FIEMAP_EXTENT_LAST
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) flag set (see the next section on extent flags).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) Each extent is described by a single fiemap_extent structure as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) returned in fm_extents::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) struct fiemap_extent {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) __u64 fe_logical; /* logical offset in bytes for the start of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) * the extent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) __u64 fe_physical; /* physical offset in bytes for the start
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) * of the extent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) __u64 fe_length; /* length in bytes for the extent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) __u64 fe_reserved64[2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) __u32 fe_reserved[3];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) All offsets and lengths are in bytes and mirror those on disk. It is valid
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) for an extents logical offset to start before the request or its logical
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) length to extend past the request. Unless FIEMAP_EXTENT_NOT_ALIGNED is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) returned, fe_logical, fe_physical, and fe_length will be aligned to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) block size of the file system. With the exception of extents flagged as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) FIEMAP_EXTENT_MERGED, adjacent extents will not be merged.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) The fe_flags field contains flags which describe the extent returned.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) A special flag, FIEMAP_EXTENT_LAST is always set on the last extent in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) the file so that the process making fiemap calls can determine when no
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) more extents are available, without having to call the ioctl again.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) Some flags are intentionally vague and will always be set in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) presence of other more specific flags. This way a program looking for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) a general property does not have to know all existing and future flags
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) which imply that property.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) For example, if FIEMAP_EXTENT_DATA_INLINE or FIEMAP_EXTENT_DATA_TAIL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) are set, FIEMAP_EXTENT_NOT_ALIGNED will also be set. A program looking
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) for inline or tail-packed data can key on the specific flag. Software
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) which simply cares not to try operating on non-aligned extents
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) however, can just key on FIEMAP_EXTENT_NOT_ALIGNED, and not have to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) worry about all present and future flags which might imply unaligned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) data. Note that the opposite is not true - it would be valid for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) FIEMAP_EXTENT_NOT_ALIGNED to appear alone.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) FIEMAP_EXTENT_LAST
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) This is generally the last extent in the file. A mapping attempt past
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) this extent may return nothing. Some implementations set this flag to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) indicate this extent is the last one in the range queried by the user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) (via fiemap->fm_length).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) FIEMAP_EXTENT_UNKNOWN
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) The location of this extent is currently unknown. This may indicate
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) the data is stored on an inaccessible volume or that no storage has
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) been allocated for the file yet.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) FIEMAP_EXTENT_DELALLOC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) This will also set FIEMAP_EXTENT_UNKNOWN.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) Delayed allocation - while there is data for this extent, its
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) physical location has not been allocated yet.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) FIEMAP_EXTENT_ENCODED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) This extent does not consist of plain filesystem blocks but is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) encoded (e.g. encrypted or compressed). Reading the data in this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) extent via I/O to the block device will have undefined results.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) Note that it is *always* undefined to try to update the data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) in-place by writing to the indicated location without the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) assistance of the filesystem, or to access the data using the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) information returned by the FIEMAP interface while the filesystem
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) is mounted. In other words, user applications may only read the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) extent data via I/O to the block device while the filesystem is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) unmounted, and then only if the FIEMAP_EXTENT_ENCODED flag is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) clear; user applications must not try reading or writing to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) filesystem via the block device under any other circumstances.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) FIEMAP_EXTENT_DATA_ENCRYPTED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) This will also set FIEMAP_EXTENT_ENCODED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) The data in this extent has been encrypted by the file system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) FIEMAP_EXTENT_NOT_ALIGNED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) Extent offsets and length are not guaranteed to be block aligned.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) FIEMAP_EXTENT_DATA_INLINE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) This will also set FIEMAP_EXTENT_NOT_ALIGNED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) Data is located within a meta data block.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) FIEMAP_EXTENT_DATA_TAIL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) This will also set FIEMAP_EXTENT_NOT_ALIGNED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) Data is packed into a block with data from other files.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) FIEMAP_EXTENT_UNWRITTEN
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) Unwritten extent - the extent is allocated but its data has not been
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) initialized. This indicates the extent's data will be all zero if read
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) through the filesystem but the contents are undefined if read directly from
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) the device.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) FIEMAP_EXTENT_MERGED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) This will be set when a file does not support extents, i.e., it uses a block
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) based addressing scheme. Since returning an extent for each block back to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) userspace would be highly inefficient, the kernel will try to merge most
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) adjacent blocks into 'extents'.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) VFS -> File System Implementation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) ---------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) File systems wishing to support fiemap must implement a ->fiemap callback on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) their inode_operations structure. The fs ->fiemap call is responsible for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) defining its set of supported fiemap flags, and calling a helper function on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) each discovered extent::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) struct inode_operations {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) u64 len);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) ->fiemap is passed struct fiemap_extent_info which describes the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) fiemap request::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) struct fiemap_extent_info {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197) unsigned int fi_flags; /* Flags as passed from user */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) unsigned int fi_extents_mapped; /* Number of mapped extents */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) unsigned int fi_extents_max; /* Size of fiemap_extent array */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) struct fiemap_extent *fi_extents_start; /* Start of fiemap_extent array */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) It is intended that the file system should not need to access any of this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) structure directly. Filesystem handlers should be tolerant to signals and return
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) EINTR once fatal signal received.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) Flag checking should be done at the beginning of the ->fiemap callback via the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) fiemap_prep() helper::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) u64 start, u64 *len, u32 supported_flags);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) The struct fieinfo should be passed in as received from ioctl_fiemap(). The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) set of fiemap flags which the fs understands should be passed via fs_flags. If
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) fiemap_prep finds invalid user flags, it will place the bad values in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) fieinfo->fi_flags and return -EBADR. If the file system gets -EBADR, from
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) fiemap_prep(), it should immediately exit, returning that error back to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) ioctl_fiemap(). Additionally the range is validate against the supported
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) maximum file size.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) For each extent in the request range, the file system should call
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) the helper function, fiemap_fill_next_extent()::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) u64 phys, u64 len, u32 flags, u32 dev);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229) fiemap_fill_next_extent() will use the passed values to populate the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) next free extent in the fm_extents array. 'General' extent flags will
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) automatically be set from specific flags on behalf of the calling file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) system so that the userspace API is not broken.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) fiemap_fill_next_extent() returns 0 on success, and 1 when the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) user-supplied fm_extents array is full. If an error is encountered
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) while copying the extent to user memory, -EFAULT will be returned.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
3 Commits
0 Branches
0 Tags