[Aide] O_NOATIME for open(2) (also O_DIRECT, O_LARGEFILE ?)

[Richard van den Berg]

Thanks for the pointers. All I need now is a way to check for O_NOATIME
using autoconf.

>From the HPUX man pages:

O_LARGEFILE 	 	

Setting O_LARGEFILE in a call to open() or creat() is equivalent to
calling open64() or creat64(), both of which set O_LARGEFILE in the file
status flags. This bit is automatically set by open() and creat() if
_FILE_OFFSET_BITS is set to 64. The bit may be queried by fcntl() (or
fcntl64()), which can also turn the bit on or off if desired.

The aide configure script tests for and sets _FILE_OFFSET_BITS to 64 in
config.h when appropriate, so using O_LARGEFILE is not needed.

Using the O_DIRECT flag would prevent aide from using the kernel disk
read cache. If I am not mistaken, aide reads each file only once (block
by block in do_md.c) and calculates all needed hashes from the block in
memory. So using O_DIRECT should not degrade performance for aide, and
it might increase overall system performance. Does anyone with a Linux
system want to test this?

Sincerely,

Richard van den Berg