Repair /proc/devices early-termination regression.
2.6.16 broke /proc/devices. An application often gets an
EOF before the end of data is reached, if that application
uses a series of short read(2)s to access the data. I have
used read buffers of varying sizes with varying degrees
of unsuccess (larger sizes get further into the data than
smaller sizes, following a simple pattern). It appears
that the only safe way to get the data is to use a single
read buffer larger than all the data in /proc/devices.
The following example demonstates the problem:
# dd if=/proc/devices bs=1
Character devices:
1 mem
27+0 records in
27+0 records out
This patch is a backport of the fix recently accepted to
Linus's tree:
commit 68eef3b479
[PATCH] Simplify proc/devices and fix early termination regression
It replaces the complex, state-machine algorithm introduced
in 2.6.16 with a simple algorithm, modeled on the implementation
of /proc/interrupts.
[akpm@osdl.org: cleanups, simplifications]
Signed-off-by: Joe Korty <joe.korty@ccur.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Andrew Morton
692c0509fd