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docs: filesystems: convert zonefs.txt to ReST
- Add a SPDX header; - Add a document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Link: https://lore.kernel.org/r/42a7cfcd19f6b904a9a3188fd4af71bed5050052.1581955849.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Mauro Carvalho Chehab
Jonathan Corbet
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9a6108124c
@ -95,3 +95,4 @@ Documentation for filesystem implementations.
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udf
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virtiofs
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vfat
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zonefs
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@ -1,4 +1,8 @@
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.. SPDX-License-Identifier: GPL-2.0
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================================================
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ZoneFS - Zone filesystem for Zoned block devices
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================================================
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Introduction
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============
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@ -29,6 +33,7 @@ Zoned block devices
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Zoned storage devices belong to a class of storage devices with an address
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space that is divided into zones. A zone is a group of consecutive LBAs and all
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zones are contiguous (there are no LBA gaps). Zones may have different types.
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* Conventional zones: there are no access constraints to LBAs belonging to
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conventional zones. Any read or write access can be executed, similarly to a
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regular block device.
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@ -158,6 +163,7 @@ Format options
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--------------
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Several optional features of zonefs can be enabled at format time.
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* Conventional zone aggregation: ranges of contiguous conventional zones can be
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aggregated into a single larger file instead of the default one file per zone.
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* File ownership: The owner UID and GID of zone files is by default 0 (root)
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@ -249,7 +255,7 @@ permissions.
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Further action taken by zonefs I/O error recovery can be controlled by the user
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with the "errors=xxx" mount option. The table below summarizes the result of
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zonefs I/O error processing depending on the mount option and on the zone
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conditions.
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conditions::
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+--------------+-----------+-----------------------------------------+
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| | | Post error state |
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@ -275,6 +281,7 @@ conditions.
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+--------------+-----------+-----------------------------------------+
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Further notes:
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* The "errors=remount-ro" mount option is the default behavior of zonefs I/O
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error processing if no errors mount option is specified.
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* With the "errors=remount-ro" mount option, the change of the file access
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@ -302,6 +309,7 @@ Mount options
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zonefs define the "errors=<behavior>" mount option to allow the user to specify
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zonefs behavior in response to I/O errors, inode size inconsistencies or zone
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condition chages. The defined behaviors are as follow:
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* remount-ro (default)
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* zone-ro
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* zone-offline
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@ -325,78 +333,78 @@ Examples
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--------
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The following formats a 15TB host-managed SMR HDD with 256 MB zones
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with the conventional zones aggregation feature enabled.
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with the conventional zones aggregation feature enabled::
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# mkzonefs -o aggr_cnv /dev/sdX
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# mount -t zonefs /dev/sdX /mnt
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# ls -l /mnt/
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total 0
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dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
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dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
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# mkzonefs -o aggr_cnv /dev/sdX
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# mount -t zonefs /dev/sdX /mnt
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# ls -l /mnt/
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total 0
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dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
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dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
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The size of the zone files sub-directories indicate the number of files
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existing for each type of zones. In this example, there is only one
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conventional zone file (all conventional zones are aggregated under a single
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file).
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file)::
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# ls -l /mnt/cnv
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total 137101312
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-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
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# ls -l /mnt/cnv
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total 137101312
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-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
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This aggregated conventional zone file can be used as a regular file.
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This aggregated conventional zone file can be used as a regular file::
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# mkfs.ext4 /mnt/cnv/0
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# mount -o loop /mnt/cnv/0 /data
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# mkfs.ext4 /mnt/cnv/0
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# mount -o loop /mnt/cnv/0 /data
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The "seq" sub-directory grouping files for sequential write zones has in this
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example 55356 zones.
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example 55356 zones::
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# ls -lv /mnt/seq
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total 14511243264
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-rw-r----- 1 root root 0 Nov 25 13:23 0
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-rw-r----- 1 root root 0 Nov 25 13:23 1
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-rw-r----- 1 root root 0 Nov 25 13:23 2
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...
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-rw-r----- 1 root root 0 Nov 25 13:23 55354
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-rw-r----- 1 root root 0 Nov 25 13:23 55355
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# ls -lv /mnt/seq
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total 14511243264
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-rw-r----- 1 root root 0 Nov 25 13:23 0
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-rw-r----- 1 root root 0 Nov 25 13:23 1
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-rw-r----- 1 root root 0 Nov 25 13:23 2
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...
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-rw-r----- 1 root root 0 Nov 25 13:23 55354
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-rw-r----- 1 root root 0 Nov 25 13:23 55355
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For sequential write zone files, the file size changes as data is appended at
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the end of the file, similarly to any regular file system.
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the end of the file, similarly to any regular file system::
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# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
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1+0 records in
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1+0 records out
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4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00044121 s, 9.3 MB/s
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# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
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1+0 records in
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1+0 records out
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4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00044121 s, 9.3 MB/s
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
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The written file can be truncated to the zone size, preventing any further
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write operation.
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write operation::
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# truncate -s 268435456 /mnt/seq/0
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
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# truncate -s 268435456 /mnt/seq/0
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
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Truncation to 0 size allows freeing the file zone storage space and restart
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append-writes to the file.
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append-writes to the file::
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# truncate -s 0 /mnt/seq/0
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
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# truncate -s 0 /mnt/seq/0
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# ls -l /mnt/seq/0
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-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
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Since files are statically mapped to zones on the disk, the number of blocks of
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a file as reported by stat() and fstat() indicates the size of the file zone.
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a file as reported by stat() and fstat() indicates the size of the file zone::
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# stat /mnt/seq/0
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File: /mnt/seq/0
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Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
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Device: 870h/2160d Inode: 50431 Links: 1
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Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
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Access: 2019-11-25 13:23:57.048971997 +0900
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Modify: 2019-11-25 13:52:25.553805765 +0900
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Change: 2019-11-25 13:52:25.553805765 +0900
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Birth: -
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# stat /mnt/seq/0
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File: /mnt/seq/0
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Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
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Device: 870h/2160d Inode: 50431 Links: 1
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Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
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Access: 2019-11-25 13:23:57.048971997 +0900
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Modify: 2019-11-25 13:52:25.553805765 +0900
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Change: 2019-11-25 13:52:25.553805765 +0900
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Birth: -
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The number of blocks of the file ("Blocks") in units of 512B blocks gives the
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maximum file size of 524288 * 512 B = 256 MB, corresponding to the device zone
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