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17 May 2024, 11:00:25 UTC
Revision 1c0b8a7a62c3d3ebf53a8e40cc6da22f5e192d63 authored by Mikulas Patocka on 28 January 2014, 23:11:33 UTC, committed by Linus Torvalds on 03 February 2014, 00:24:07 UTC 
hpfs: optimize quad buffer loading
 
HPFS needs to load 4 consecutive 512-byte sectors when accessing the
directory nodes or bitmaps.  We can't switch to 2048-byte block size
because files are allocated in the units of 512-byte sectors.

Previously, the driver would allocate a 2048-byte area using kmalloc,
copy the data from four buffers to this area and eventually copy them
back if they were modified.

In the current implementation of the buffer cache, buffers are allocated
in the pagecache.  That means that 4 consecutive 512-byte buffers are
stored in consecutive areas in the kernel address space.  So, we don't
need to allocate extra memory and copy the content of the buffers there.

This patch optimizes the code to avoid copying the buffers.  It checks
if the four buffers are stored in contiguous memory - if they are not,
it falls back to allocating a 2048-byte area and copying data there.

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 2cbe5c7
History
Tip revision: 1c0b8a7a62c3d3ebf53a8e40cc6da22f5e192d63 authored by Mikulas Patocka on 28 January 2014, 23:11:33 UTC
hpfs: optimize quad buffer loading
Tip revision: 1c0b8a7
File Mode Size
Documentation
arch
block
crypto
drivers
firmware
fs
include
init
ipc
kernel
lib
mm
net
samples
scripts
security
sound
tools
usr
virt
.gitignore -rw-r--r-- 1.1 KB
.mailmap -rw-r--r-- 4.4 KB
COPYING -rw-r--r-- 18.3 KB
CREDITS -rw-r--r-- 93.3 KB
Kbuild -rw-r--r-- 2.5 KB
Kconfig -rw-r--r-- 252 bytes
MAINTAINERS -rw-r--r-- 266.4 KB
Makefile -rw-r--r-- 49.1 KB
README -rw-r--r-- 18.3 KB
REPORTING-BUGS -rw-r--r-- 7.3 KB

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