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Documentation: dm-integrity: Document the meaning of "buffer". 

"Buffers" are buffers of the metadata/checksum area of dm-integrity.
They are always at most as large as a single metadata area on-disk, but
may be smaller.

Signed-off-by: Russell Harmon <eatnumber1@gmail.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Russell Harmon 2023-06-04 22:08:51 -07:00 committed by Mike Snitzer
parent c3ba5aa6f7
commit 3b671459e6
1 changed files with 9 additions and 4 deletions
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13
Documentation/admin-guide/device-mapper/dm-integrity.rst
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@ -38,6 +38,15 @@ the device. But it will only format the device if the superblock contains
zeroes. If the superblock is neither valid nor zeroed, the dm-integrity
target can't be loaded.
Accesses to the on-disk metadata area containing checksums (aka tags) are
buffered using dm-bufio. When an access to any given metadata area
occurs, each unique metadata area gets its own buffer(s). The buffer size
is capped at the size of the metadata area, but may be smaller, thereby
requiring multiple buffers to represent the full metadata area. A smaller
buffer size will produce a smaller resulting read/write operation to the
metadata area for small reads/writes. The metadata is still read even in
a full write to the data covered by a single buffer.
To use the target for the first time:
1. overwrite the superblock with zeroes
@ -106,10 +115,6 @@ buffer_sectors:number
The number of sectors in one buffer. The value is rounded down to
a power of two.
The tag area is accessed using buffers, the buffer size is
configurable. The large buffer size means that the I/O size will
be larger, but there could be less I/Os issued.
journal_watermark:number
The journal watermark in percents. When the size of the journal
exceeds this watermark, the thread that flushes the journal will