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nfsd: support ext4 i_version

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ext4 supports a real NFSv4 change attribute, which is bumped whenever
the ctime would be updated, including times when two updates arrive
within a jiffy of each other.  (Note that although ext4 has space for
nanosecond-precision ctime, the real resolution is lower: it actually
uses jiffies as the time-source.)  This ensures clients will invalidate
their caches when they need to.

There is some fear that keeping the i_version up-to-date could have
performance drawbacks, so for now it's turned on only by a mount option.
We hope to do something better eventually.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Theodore Tso <tytso@mit.edu>
This commit is contained in:
J. Bruce Fields
2009-04-16 17:33:25 -04:00
parent 3352d2c2d0
commit c654b8a9cb
4 changed files with 63 additions and 25 deletions
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17
include/linux/nfsd/xdr4.h
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@@ -64,10 +64,13 @@ static inline bool nfsd4_has_session(struct nfsd4_compound_state *cs)
struct nfsd4_change_info {
u32 atomic;
bool change_supported;
u32 before_ctime_sec;
u32 before_ctime_nsec;
u64 before_change;
u32 after_ctime_sec;
u32 after_ctime_nsec;
u64 after_change;
};
struct nfsd4_access {
@@ -503,10 +506,16 @@ set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
{
BUG_ON(!fhp->fh_pre_saved || !fhp->fh_post_saved);
cinfo->atomic = 1;
cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
cinfo->change_supported = IS_I_VERSION(fhp->fh_dentry->d_inode);
if (cinfo->change_supported) {
cinfo->before_change = fhp->fh_pre_change;
cinfo->after_change = fhp->fh_post_change;
} else {
cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
}
}
int nfs4svc_encode_voidres(struct svc_rqst *, __be32 *, void *);