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| /Documentation/filesystems/ext4/ |
| D | directory.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 -----------------
7 an arbitrary byte string (usually ASCII) to an inode number on the
9 that reference the same inode number--these are known as hard links, and
11 such, directory entries are found by reading the data block(s)
18 By default, each directory lists its entries in an “almost-linear”
22 data blocks and that each block contains a linear array of directory
23 entries. The end of each per-block array is signified by reaching the
24 end of the block; the last entry in the block has a record length that
25 takes it all the way to the end of the block. The end of the entire
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| D | ifork.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 ------------------------------
8 regular files and directories will use it for file block indexing
15 string is less than 60 bytes long. Otherwise, either extents or block
18 Direct/Indirect Block Addressing
21 In ext2/3, file block numbers were mapped to logical block numbers by
22 means of an (up to) three level 1-1 block map. To find the logical block
23 that stores a particular file block, the code would navigate through
25 magic number nor a checksum to provide any level of confidence that the
26 block isn't full of garbage.
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| D | mmp.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 -------------------------
10 sequence number. If the sequence number is EXT4_MMP_SEQ_CLEAN, the
11 open continues. If the sequence number is EXT4_MMP_SEQ_FSCK, then
14 the sequence number again. If the sequence number has changed, then the
16 code passes all of those checks, a new MMP sequence number is generated
17 and written to the MMP block, and the mount proceeds.
19 While the filesystem is live, the kernel sets up a timer to re-check the
20 MMP block at the specified MMP check interval. To perform the re-check,
21 the MMP sequence number is re-read; if it does not match the in-memory
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| D | journal.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 --------------
10 “important” data writes on-disk as quickly as possible. Once the important
15 read-write-erases) before erasing the commit record. Should the system
45 consumes an entire block group, though mke2fs tries to put it in the
48 All fields in jbd2 are written to disk in big-endian order. This is the
61 .. list-table::
63 :header-rows: 1
65 * - Superblock
66 - descriptor_block (data_blocks or revocation_block) [more data or
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| D | attributes.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 -------------------
7 block on the disk and referenced from inodes via ``inode.i_file_acl*``.
17 sb.inode_size = 256, then there are 256 - (128 + 28) = 100 bytes
18 available for in-inode extended attribute storage. The second place
19 where extended attributes can be found is in the block pointed to by
21 block to contain a pointer to a second extended attribute block (or even
23 attribute's value to be stored in a separate data block, though as of
32 .. list-table::
34 :header-rows: 1
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| D | super.rst | 1 .. SPDX-License-Identifier: GPL-2.0
3 Super Block
4 -----------
7 filesystem, such as block counts, inode counts, supported features,
12 number is either 0 or a power of 3, 5, or 7. If the flag is not set,
21 .. list-table::
23 :header-rows: 1
25 * - Offset
26 - Size
27 - Name
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| D | checksums.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 ---------
10 structures did not have space to fit a full 32-bit checksum, so only the
12 structure size so that full 32-bit checksums can be stored for many data
13 structures. However, existing 32-bit filesystems cannot be extended to
18 ``tune2fs -O metadata_csum`` against the underlying device. If tune2fs
20 checksum, it will request that you run ``e2fsck -D`` to have the
30 .. list-table::
32 :header-rows: 1
34 * - Metadata
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| /Documentation/admin-guide/device-mapper/ |
| D | dm-zoned.rst | 2 dm-zoned
5 The dm-zoned device mapper target exposes a zoned block device (ZBC and
6 ZAC compliant devices) as a regular block device without any write
7 pattern constraints. In effect, it implements a drive-managed zoned
8 block device which hides from the user (a file system or an application
9 doing raw block device accesses) the sequential write constraints of
10 host-managed zoned block devices and can mitigate the potential
11 device-side performance degradation due to excessive random writes on
12 host-aware zoned block devices.
14 For a more detailed description of the zoned block device models and
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| D | dm-ebs.rst | 2 dm-ebs
7 a smaller logical block size on a device with a larger logical block
11 Supported emulated logical block sizes 512, 1024, 2048 and 4096.
13 Underlying block size can be set to > 4K to test buffering larger units.
17 ----------------
23 Full pathname to the underlying block-device,
24 or a "major:minor" device-number.
29 Number of sectors defining the logical block size to be emulated;
35 Number of sectors defining the logical block size of <dev path>.
37 If not provided, the logical block size of <dev path> will be used.
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| D | cache.rst | 8 dm-cache is a device mapper target written by Joe Thornber, Heinz
11 It aims to improve performance of a block device (eg, a spindle) by
15 This device-mapper solution allows us to insert this caching at
17 a thin-provisioning pool. Caching solutions that are integrated more
20 The target reuses the metadata library used in the thin-provisioning
23 The decision as to what data to migrate and when is left to a plug-in
32 Movement of the primary copy of a logical block from one
39 The origin device always contains a copy of the logical block, which
46 Sub-devices
47 -----------
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| D | writecache.rst | 14 1. type of the cache device - "p" or "s"
15 - p - persistent memory
16 - s - SSD
19 4. block size (4096 is recommended; the maximum block size is the page
21 5. the number of optional parameters (the parameters with an argument
25 offset from the start of cache device in 512-byte sectors
27 start writeback when the number of used blocks reach this
30 stop writeback when the number of used blocks drops below
33 limit the number of blocks that are in flight during
45 applicable only to persistent memory - use the FUA flag
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| D | verity.rst | 2 dm-verity
5 Device-Mapper's "verity" target provides transparent integrity checking of
6 block devices using a cryptographic digest provided by the kernel crypto API.
7 This target is read-only.
21 This is the type of the on-disk hash format.
25 the rest of the block is padded with zeroes.
33 checked. It may be specified as a path, like /dev/sdaX, or a device number,
40 dm-verity device.
43 The block size on a data device in bytes.
44 Each block corresponds to one digest on the hash device.
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| /Documentation/devicetree/bindings/dma/ |
| D | fsl-qdma.yaml | 1 # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
3 ---
4 $id: http://devicetree.org/schemas/dma/fsl-qdma.yaml#
5 $schema: http://devicetree.org/meta-schemas/core.yaml#
10 - Frank Li <Frank.Li@nxp.com>
15 - const: fsl,ls1021a-qdma
16 - items:
17 - enum:
18 - fsl,ls1028a-qdma
19 - fsl,ls1043a-qdma
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| /Documentation/block/ |
| D | stat.rst | 2 Block layer statistics in /sys/block/<dev>/stat
5 This file documents the contents of the /sys/block/<dev>/stat file.
7 The stat file provides several statistics about the state of block
29 read I/Os requests number of read I/Os processed
30 read merges requests number of read I/Os merged with in-queue I/O
31 read sectors sectors number of sectors read
33 write I/Os requests number of write I/Os processed
34 write merges requests number of write I/Os merged with in-queue I/O
35 write sectors sectors number of sectors written
37 in_flight requests number of I/Os currently in flight
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| D | blk-mq.rst | 1 .. SPDX-License-Identifier: GPL-2.0
4 Multi-Queue Block IO Queueing Mechanism (blk-mq)
7 The Multi-Queue Block IO Queueing Mechanism is an API to enable fast storage
8 devices to achieve a huge number of input/output operations per second (IOPS)
9 through queueing and submitting IO requests to block devices simultaneously,
16 ----------
19 development of the kernel. The Block IO subsystem aimed to achieve the best
26 However, with the development of Solid State Drives and Non-Volatile Memories
30 in those devices' design, the multi-queue mechanism was introduced.
32 The former design had a single queue to store block IO requests with a single
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| /Documentation/ABI/stable/ |
| D | sysfs-block | 1 What: /sys/block/<disk>/alignment_offset
5 Storage devices may report a physical block size that is
6 bigger than the logical block size (for instance a drive
7 with 4KB physical sectors exposing 512-byte logical
13 What: /sys/block/<disk>/discard_alignment
19 the exported logical block size. The discard_alignment
24 What: /sys/block/<disk>/atomic_write_max_bytes
31 operation must not exceed this number of bytes.
35 power-of-two and atomic_write_unit_max_bytes may also be
37 This parameter - along with atomic_write_unit_min_bytes
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| /Documentation/driver-api/nvdimm/ |
| D | btt.rst | 2 BTT - Block Translation Table
11 storage as traditional block devices. The block drivers for persistent memory
14 using stored energy in capacitors to complete in-flight block writes, or perhaps
15 in firmware. We don't have this luxury with persistent memory - if a write is in
16 progress, and we experience a power failure, the block will contain a mix of old
19 The Block Translation Table (BTT) provides atomic sector update semantics for
21 being torn can continue to do so. The BTT manifests itself as a stacked block
23 the heart of it, is an indirection table that re-maps all the blocks on the
37 next arena). The following depicts the "On-disk" metadata layout::
40 Backing Store +-------> Arena
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| /Documentation/devicetree/bindings/powerpc/fsl/ |
| D | mpic-msgr.txt | 9 - compatible: Specifies the compatibility list for the message register
10 block. The type shall be <string-list> and the value shall be of the form
11 "fsl,mpic-v<version>-msgr", where <version> is the version number of
14 - reg: Specifies the base physical address(s) and size(s) of the
15 message register block's addressable register space. The type shall be
16 <prop-encoded-array>.
18 - interrupts: Specifies a list of interrupt-specifiers which are available
19 for receiving interrupts. Interrupt-specifier consists of two cells: first
20 cell is interrupt-number and second cell is level-sense. The type shall be
21 <prop-encoded-array>.
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| /Documentation/admin-guide/blockdev/ |
| D | zram.rst | 2 zram: Compressed RAM-based block devices
8 The zram module creates RAM-based block devices named /dev/zram<id>
15 /sys/block/zram<id>/
20 There are several ways to configure and manage zram device(-s):
23 b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org).
28 In order to get a better idea about zramctl please consult util-linux
29 documentation, zramctl man-page or `zramctl --help`. Please be informed
30 that zram maintainers do not develop/maintain util-linux or zramctl, should
31 you have any questions please contact util-linux@vger.kernel.org
45 -EBUSY an attempt to modify an attribute that cannot be changed once
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| /Documentation/scsi/ |
| D | st.rst | 1 .. SPDX-License-Identifier: GPL-2.0
23 flexible method and applicable to single-user workstations. However,
28 parameters, like block size and density using the MTSETDRVBUFFER ioctl.
32 drive performs auto-detection of the tape format well (like some
33 QIC-drives). The result is that any tape can be read, writing can be
37 does not perform auto-detection well enough and there is a single
39 used only in variable block mode (I don't know if this is sensible
40 or not :-).
47 number (bits 5 and 6). The number of modes can be changed by changing
57 between formats in multi-tape operations (the explicitly overridden
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| /Documentation/admin-guide/ |
| D | pstore-blk.rst | 1 .. SPDX-License-Identifier: GPL-2.0
3 pstore block oops/panic logger
7 ------------
9 pstore block (pstore/blk) is an oops/panic logger that writes its logs to a
10 block device and non-block device before the system crashes. You can get
13 mount -t pstore pstore /sys/fs/pstore
16 pstore block concepts
17 ---------------------
27 Configurations for driver are all about block device and non-block device,
28 such as total_size of block device and read/write operations.
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| /Documentation/filesystems/ |
| D | qnx6.rst | 1 .. SPDX-License-Identifier: GPL-2.0
29 ------
39 ---------------
42 Each qnx6fs got two superblocks, each one having a 64bit serial number.
43 That serial number is used to identify the "active" superblock.
48 update of the serial number. Before updating that serial, all modifications
61 addressing block holds up to blocksize / 4 bytes pointers to data blocks.
62 Level 2 adds an additional indirect addressing block level (so, already up
65 Unused block pointers are always set to ~0 - regardless of root node,
75 information (total number of filesystem blocks) or by taking the highest
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| /Documentation/staging/ |
| D | lzo.rst | 23 opcode and on the number of literals copied by previous instruction. The
26 - a distance when copying data from the dictionary (past output buffer)
27 - a length (number of bytes to copy from dictionary)
28 - the number of literals to copy, which is retained in variable "state"
35 The first byte of the block follows a different encoding from other bytes, it
39 Lengths are always encoded on a variable size starting with a small number
40 of bits in the operand. If the number of bits isn't enough to represent the
45 length = byte & ((1 << #bits) - 1)
47 length = ((1 << #bits) - 1)
48 length += 255*(number of zero bytes)
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| /Documentation/userspace-api/media/dvb/ |
| D | frontend-stat-properties.rst | 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3 .. _frontend-stat-properties:
27 The number of filled elements are stored at ``dtv_property.stat.len``.
32 - ``svalue`` or ``uvalue``, where ``svalue`` is for signed values of
36 - ``scale`` - Scale for the value. It can be:
38 - ``FE_SCALE_NOT_AVAILABLE`` - The parameter is supported by the
42 - ``FE_SCALE_DECIBEL`` - parameter is a signed value, measured in
45 - ``FE_SCALE_RELATIVE`` - parameter is a unsigned value, where 0
48 - ``FE_SCALE_COUNTER`` - parameter is a unsigned value that counts
49 the occurrence of an event, like bit error, block error, or lapsed
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| /Documentation/filesystems/xfs/ |
| D | xfs-self-describing-metadata.rst | 1 .. SPDX-License-Identifier: GPL-2.0
44 magic number in the metadata block, we have no other way of identifying what it
46 you can't look at a single metadata block in isolation and say "yes, it is
52 understanding how things like cross linked block lists (e.g. sibling
65 location. This allows us to identify the expected contents of the block and
70 Luckily, almost all XFS metadata has magic numbers embedded already - only the
72 magic numbers. Hence we can change the on-disk format of all these objects to
74 numbers in the metadata objects. That is, if it has the current magic number,
75 the metadata isn't self identifying. If it contains a new magic number, it is
83 block. If we can verify the block contains the metadata it was intended to
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