On 02/08/2022 14.37, Ulrich Windl wrote:
"Fabio M. Di Nitto" <fabbi...@fabbione.net> schrieb am 02.08.2022 um 14:30
in
Nachricht <0b26c097-1e21-3945-24ba-355cd0ccf...@fabbione.net>:
Hello Kazunori-san,
On 02/08/2022 12.13, 井上和徳 wrote:
Hi,
Since O_DIRECT is not specified in open() [1], it reads the buffer cache
and
may result in a false negative. I fear that this possibility increases
in environments with large buffer cache and running disk-reading
applications
such as database.
So, I think it's better to specify O_RDONLY|O_DIRECT, but what about it?
(in this case, lseek() processing is unnecessary.)
I will have to defer to Christine (in CC) to this email on why we didn´t
use O_DIRECT.
I have a vague recollection that some storage devices didn´t like the
O_DIRECT option causing other issues later, but it´s been a while since
I touched the code.
The thing with O_DIRECT is that a "software block" has to be a multiple of a
"hardware block"; i.e: you cannot read a partial block, and the buffer has some
alignment requirements.
that was it! thanks for refreshing my memory.
Fabio
# I am ready to create a patch that works with O_DIRECT. Also, I wouldn't
mind
# a "change to add a new mode of inspection with O_DIRECT
# (add a option to storage_mon) while keeping the current inspection
process".
[1]
https://github.com/ClusterLabs/resource-agents/blob/main/tools/storage_mon.c#
L47-L90
It might be a very reasonable solution, tho let´s wait for an answer
from Chrissie.
Cheers
Fabio
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