Lines Matching +full:read +full:- +full:only
1 .. SPDX-License-Identifier: GPL-2.0
4 ZoneFS - Zone filesystem for Zoned block devices
11 as a file. Unlike a regular POSIX-compliant file system with native zoned block
15 of the file (append only writes).
18 than to a full-featured POSIX file system. The goal of zonefs is to simplify
22 example of this approach is the implementation of LSM (log-structured merge)
31 -------------------
38 conventional zones. Any read or write access can be executed, similarly to a
62 by sub-directories. This file structure is built entirely using zone information
63 provided by the device and so does not require any complex on-disk metadata
66 On-disk metadata
67 ----------------
69 zonefs on-disk metadata is reduced to an immutable super block which
80 state to make it read-only, preventing any data write.
82 Zone type sub-directories
83 -------------------------
86 sub-directory automatically created on mount.
88 For conventional zones, the sub-directory "cnv" is used. This directory is
89 however created if and only if the device has usable conventional zones. If
90 the device only has a single conventional zone at sector 0, the zone will not
92 such devices, the "cnv" sub-directory will not be created.
94 For sequential write zones, the sub-directory "seq" is used.
96 These two directories are the only directories that exist in zonefs. Users
98 "seq" sub-directories.
105 ----------
112 All read and write operations to zone files are not allowed beyond the file
114 capacity is failed with the -EFBIG error.
117 sub-directories is not allowed.
123 -----------------------
128 These files can be randomly read and written using any type of I/O operation:
133 ---------------------
135 The size of sequential zone files grouped in the "seq" sub-directory represents
138 Sequential zone files can only be written sequentially, starting from the file
139 end, that is, write operations can only be append writes. Zonefs makes no
142 write issued and still in-flight (for asynchronous I/O operations).
146 on sequential files. Only direct I/O writes are accepted for these files.
150 must be used. This type of elevator (e.g. mq-deadline) is set by default
153 There are no restrictions on the type of I/O used for read operations in
154 sequential zone files. Buffered I/Os, direct I/Os and shared read mappings are
157 Truncating sequential zone files is allowed only down to 0, in which case, the
163 --------------
174 -----------------
181 * A zone may transition to the read-only condition (BLK_ZONE_COND_READONLY):
184 read/write access) can change the zone condition back to a normal read/write
185 state. While the reasons for the device to transition a zone to read-only
188 changed to read-only).
191 An offline zone cannot be read nor written. No user action can transition an
192 offline zone back to an operational good state. Similarly to zone read-only
194 condition are undefined. A typical cause would be a defective read-write head
217 actions taken by zonefs in response to I/O errors depend on the I/O type (read
221 * For read I/O errors, zonefs does not execute any particular recovery action,
222 but only if the file zone is still in a good condition and there is no
228 * A zone condition change to read-only or offline also always triggers zonefs
237 the file zone. For instance, the partial failure of a multi-BIO large write
250 A zone condition change to read-only is indicated with a change in the file
251 access permissions to render the file read-only. This disables changes to the
253 (read and write) to the file are disabled.
260 +--------------+-----------+-----------------------------------------+
264 | option | condition | size read write read write |
265 +--------------+-----------+-----------------------------------------+
267 | remount-ro | read-only | as is yes no yes no |
269 +--------------+-----------+-----------------------------------------+
271 | zone-ro | read-only | as is yes no yes no |
273 +--------------+-----------+-----------------------------------------+
275 | zone-offline | read-only | 0 no no yes no |
277 +--------------+-----------+-----------------------------------------+
279 | repair | read-only | as is yes no yes no |
281 +--------------+-----------+-----------------------------------------+
285 * The "errors=remount-ro" mount option is the default behavior of zonefs I/O
287 * With the "errors=remount-ro" mount option, the change of the file access
288 permissions to read-only applies to all files. The file system is remounted
289 read-only.
294 * File access permission changes to read-only due to the device transitioning
295 zones to the read-only condition are permanent. Remounting or reformatting
296 the device will not re-enable file write access.
297 * File access permission changes implied by the remount-ro, zone-ro and
298 zone-offline mount options are temporary for zones in a good condition.
301 * The repair mount option triggers only the minimal set of I/O error recovery
303 indicated as being read-only or offline by the device still imply changes to
307 -------------
311 * explicit-open
320 * remount-ro (default)
321 * zone-ro
322 * zone-offline
325 The run-time I/O error actions defined for each behavior are detailed in the
327 The handling of read-only zones also differs between mount-time and run-time.
328 If a read-only zone is found at mount time, the zone is always treated in the
330 file size set to 0. This is necessary as the write pointer of read-only zones
333 read-only zone discovered at run-time, as indicated in the previous section.
336 "explicit-open" option
346 To avoid these potential errors, the "explicit-open" mount option forces zones
350 "explicit-open" mount option will result in a zone close command being issued
355 ------------------------
368 state of other zones. When the *explicit-open* mount option is used, zonefs
373 zone files open for writing. When the "explicit-open" mount option is used,
374 this number can never exceed *max_wro_seq_files*. If the *explicit-open*
382 is explicitly open (which happens only if the *explicit-open* mount option is
389 *nr_active_seq_files*, regardless of the use of the *explicit-open* mount
398 https://github.com/damien-lemoal/zonefs-tools
400 zonefs-tools also includes a test suite which can be run against any zoned
404 --------
406 The following formats a 15TB host-managed SMR HDD with 256 MB zones
409 # mkzonefs -o aggr_cnv /dev/sdX
410 # mount -t zonefs /dev/sdX /mnt
411 # ls -l /mnt/
413 dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
414 dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
416 The size of the zone files sub-directories indicate the number of files
417 existing for each type of zones. In this example, there is only one
421 # ls -l /mnt/cnv
423 -rw-r----- 1 root root 140391743488 Nov 25 13:23 0
428 # mount -o loop /mnt/cnv/0 /data
430 The "seq" sub-directory grouping files for sequential write zones has in this
433 # ls -lv /mnt/seq
435 -rw-r----- 1 root root 0 Nov 25 13:23 0
436 -rw-r----- 1 root root 0 Nov 25 13:23 1
437 -rw-r----- 1 root root 0 Nov 25 13:23 2
439 -rw-r----- 1 root root 0 Nov 25 13:23 55354
440 -rw-r----- 1 root root 0 Nov 25 13:23 55355
450 # ls -l /mnt/seq/0
451 -rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
456 # truncate -s 268435456 /mnt/seq/0
457 # ls -l /mnt/seq/0
458 -rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
461 append-writes to the file::
463 # truncate -s 0 /mnt/seq/0
464 # ls -l /mnt/seq/0
465 -rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
475 Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
476 Access: 2019-11-25 13:23:57.048971997 +0900
477 Modify: 2019-11-25 13:52:25.553805765 +0900
478 Change: 2019-11-25 13:52:25.553805765 +0900
479 Birth: -