Lines Matching +full:no +full:- +full:unaligned +full:- +full:direct +full:- +full:access
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
17 As such, zonefs is in essence closer to a raw block device access interface
18 than to a full-featured POSIX file system. The goal of zonefs is to simplify
21 direct block device file ioctls which may be more obscure to developers. One
22 example of this approach is the implementation of LSM (log-structured merge)
31 -------------------
35 zones are contiguous (there are no LBA gaps). Zones may have different types.
37 * Conventional zones: there are no access constraints to LBAs belonging to
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
92 such devices, the "cnv" sub-directory will not be created.
94 For sequential write zones, the sub-directory "seq" is used.
98 "seq" sub-directories.
105 ----------
113 maximum size, that is, beyond the zone capacity. Any access exceeding the zone
114 capacity is failed with the -EFBIG error.
117 sub-directories is not allowed.
123 -----------------------
129 buffered I/Os, direct I/Os, memory mapped I/Os (mmap), etc. There are no I/O
133 ---------------------
135 The size of sequential zone files grouped in the "seq" sub-directory represents
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
163 --------------
171 * File access permissions: the default 640 access permissions can be changed.
174 -----------------
181 * A zone may transition to the read-only condition (BLK_ZONE_COND_READONLY):
183 no longer be written. No user action on the zone (zone management command or
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
198 * Unaligned write errors: These errors result from the host issuing write
201 enforces sequential file write for sequential zones, unaligned write errors
202 may still happen in the case of a partial failure of a very large direct I/O
206 become unaligned and fail.
211 Similarly to the previous immediate unaligned write error case, delayed write
218 vs write) and on the reason for the error (bad sector, unaligned writes or zone
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
231 Zonefs minimal I/O error recovery may change a file size and file access
237 the file zone. For instance, the partial failure of a multi-BIO large write
249 * Access permission changes:
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
260 +--------------+-----------+-----------------------------------------+
262 | "errors=xxx" | device | access permissions |
265 +--------------+-----------+-----------------------------------------+
266 | | good | fixed yes no yes yes |
267 | remount-ro | read-only | as is yes no yes no |
268 | (default) | offline | 0 no no no no |
269 +--------------+-----------+-----------------------------------------+
270 | | good | fixed yes no yes yes |
271 | zone-ro | read-only | as is yes no yes no |
272 | | offline | 0 no no no no |
273 +--------------+-----------+-----------------------------------------+
274 | | good | 0 no no yes yes |
275 | zone-offline | read-only | 0 no no yes no |
276 | | offline | 0 no no no no |
277 +--------------+-----------+-----------------------------------------+
279 | repair | read-only | as is yes no yes no |
280 | | offline | 0 no no no no |
281 +--------------+-----------+-----------------------------------------+
285 * The "errors=remount-ro" mount option is the default behavior of zonefs I/O
286 error processing if no errors mount option is specified.
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.
290 * Access permission and file size changes due to the device transitioning zones
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.
300 (format time values) access rights to the files affected.
303 indicated as being read-only or offline by the device still imply changes to
304 the zone file access permissions as noted in the table above.
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 ------------------------
366 supports. A value of 0 means that the device has no limit and that any zone
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
384 the device supports. A value of 0 means that the mounted device has no limit
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
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
445 # dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
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: -