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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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7
include/linux/nfsd/nfsfh.h
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@@ -151,9 +151,15 @@ typedef struct svc_fh {
__u64 fh_pre_size; /* size before operation */
struct timespec fh_pre_mtime; /* mtime before oper */
struct timespec fh_pre_ctime; /* ctime before oper */
/*
* pre-op nfsv4 change attr: note must check IS_I_VERSION(inode)
* to find out if it is valid.
*/
u64 fh_pre_change;
/* Post-op attributes saved in fh_unlock */
struct kstat fh_post_attr; /* full attrs after operation */
u64 fh_post_change; /* nfsv4 change; see above */
#endif /* CONFIG_NFSD_V3 */
} svc_fh;
@@ -298,6 +304,7 @@ fill_pre_wcc(struct svc_fh *fhp)
fhp->fh_pre_mtime = inode->i_mtime;
fhp->fh_pre_ctime = inode->i_ctime;
fhp->fh_pre_size = inode->i_size;
fhp->fh_pre_change = inode->i_version;
fhp->fh_pre_saved = 1;
}
}