Thanks for your explanation.
Here is the reason why I want to clearfy the difference between Fs and Fr
1. When I open and read a file, Client::_open() will send a
MetaRequest(CEPH_MDS_OP_OPEN) message to Server.
2. If I try to open this file during 5s, Client::_open() will not send
MetaRequest to MDS.
3. If I try to open this file after 5s, Client::_open() will send
MetaRequest to MDS, even though the file inode and dentry informations
exist in client cache.
And here is my question:
1. client_caps_release_delay is 5s by default. If I increase this
number, client will not send MetaRequest(CEPH_MDS_OP_OPEN) too many
times. Is it OK that I set this value very big, e.g 1h? Is there any
bad influence?
2. in Client::check_caps()
{
wanted = in->caps_wanted(); //it will be 0 after release file
if (wanted)
retain |= CEPH_CAP_ANY;
else
retain |= CEPH_CAP_ANY_SHARED; //why exclude FILE_RD??
//this will cause drop FILE_RD in below code, so in next
Client::_open() see the cap don't have Fr, it will send a
MetaRequest(CEPH_MDS_OP_OPEN) to MSD
}
My question is : Is is OK to set retain |= (CEPH_CAP_ANY_SHARED |
CEPH_CAP_FILE_RD) ?
Thanks,
On Tue, Nov 6, 2018 at 6:52 AM Gregory Farnum <gfarnum@xxxxxxxxxx> wrote:
>
> On Sun, Nov 4, 2018 at 10:31 AM Marvin Zhang <fanzier@xxxxxxxxx> wrote:
> >
> > Hi guys,
> > They look very similar from defination. Can anyone tell me the difference?
> >
> > Here are defination:
> > #define CEPH_CAP_FILE_SHARED (CEPH_CAP_GSHARED << CEPH_CAP_SFILE)
> > #define CEPH_CAP_FILE_RD (CEPH_CAP_GRD << CEPH_CAP_SFILE)
> >
> > #define CEPH_CAP_GSHARED 1 /* client can reads */
> > #define CEPH_CAP_GRD 8 /* (file) client can read */
>
> IIRC, GSHARED applies to all capability types (Authority, Xattr, File,
> and whatever I'm forgetting) whereas GRD is just for File.
> In terms of FILE_SHARED versus FILE_RD: FILE_RD means the client is
> allowed to actually do data reads to the OSDs. FILE_SHARED relates
> to...whatever else that cap covers? Maybe the layout or file size?
>
> In particular, if multiple clients hold a file open and are doing
> activity on it, they will hold the Fs (FILE_SHARED) cap throughout the
> duration. But if one client is doing reads and one client is doing
> writes, the reader will be granted the Fr (FILE_RD) cap to perform its
> reads, and then have Fr revoked while its opposite number is granted
> Fw (FILE_WR) in order to perform writes.
> -Greg
