[dm-devel] [PATCH v3 2/4] Documents the meaning of "buffer" in dm-integrity.

[Russell Harmon <eatnumber1@gmail.com>]

"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>
---
 .../admin-guide/device-mapper/dm-integrity.rst      | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/device-mapper/dm-integrity.rst b/Documentation/admin-guide/device-mapper/dm-integrity.rst
index b2a698e955a3..31f514675809 100644
--- a/Documentation/admin-guide/device-mapper/dm-integrity.rst
+++ b/Documentation/admin-guide/device-mapper/dm-integrity.rst
@@ -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
-- 
2.34.1

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