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nfsd: fix NFSv4 time_delta attribute 

Currently we return the worst-case value of 1 second in the time delta
attribute.  That's not terribly useful.  Instead, return a value
calculated from the time granularity supported by the filesystem and the
system clock.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2018-04-25 14:34:11 -04:00
parent d6ebf5088f
commit 16945141c3
1 changed files with 26 additions and 3 deletions
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29
fs/nfsd/nfs4xdr.c
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@ -2006,6 +2006,31 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
return p;
}
/*
* ctime (in NFSv4, time_metadata) is not writeable, and the client
* doesn't really care what resolution could theoretically be stored by
* the filesystem.
*
* The client cares how close together changes can be while still
* guaranteeing ctime changes. For most filesystems (which have
* timestamps with nanosecond fields) that is limited by the resolution
* of the time returned from current_time() (which I'm assuming to be
* 1/HZ).
*/
static __be32 *encode_time_delta(__be32 *p, struct inode *inode)
{
struct timespec ts;
u32 ns;
ns = max_t(u32, NSEC_PER_SEC/HZ, inode->i_sb->s_time_gran);
ts = ns_to_timespec(ns);
p = xdr_encode_hyper(p, ts.tv_sec);
*p++ = cpu_to_be32(ts.tv_nsec);
return p;
}
static __be32 *encode_cinfo(__be32 *p, struct nfsd4_change_info *c)
{
*p++ = cpu_to_be32(c->atomic);
@ -2797,9 +2822,7 @@ out_acl:
p = xdr_reserve_space(xdr, 12);
if (!p)
goto out_resource;
*p++ = cpu_to_be32(0);
*p++ = cpu_to_be32(1);
*p++ = cpu_to_be32(0);
p = encode_time_delta(p, d_inode(dentry));
}
if (bmval1 & FATTR4_WORD1_TIME_METADATA) {
p = xdr_reserve_space(xdr, 12);