nfsd: support ext4 i_version

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>

2 files changed, 43 insertions, 21 deletions

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 17d0dd997204..01d4ec1c88e0 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -272,6 +272,7 @@ void fill_post_wcc(struct svc_fh *fhp)
 
         err = vfs_getattr(fhp->fh_export->ex_path.mnt, fhp->fh_dentry,
                         &fhp->fh_post_attr);
+        fhp->fh_post_change = fhp->fh_dentry->d_inode->i_version;
         if (err)
                 fhp->fh_post_saved = 0;
         else
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 4a71fcd3f036..12d36a7361cd 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1490,13 +1490,41 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
         memcpy(p, ptr, nbytes);                                 \
         p += XDR_QUADLEN(nbytes);                               \
 }} while (0)
-#define WRITECINFO(c)           do {                            \
-        *p++ = htonl(c.atomic);                                 \
-        *p++ = htonl(c.before_ctime_sec);                               \
-        *p++ = htonl(c.before_ctime_nsec);                              \
-        *p++ = htonl(c.after_ctime_sec);                                \
-        *p++ = htonl(c.after_ctime_nsec);                               \
-} while (0)
+
+static void write32(__be32 **p, u32 n)
+{
+        *(*p)++ = n;
+}
+
+static void write64(__be32 **p, u64 n)
+{
+        write32(p, (u32)(n >> 32));
+        write32(p, (u32)n);
+}
+
+static void write_change(__be32 **p, struct kstat *stat, struct inode *inode)
+{
+        if (IS_I_VERSION(inode)) {
+                write64(p, inode->i_version);
+        } else {
+                write32(p, stat->ctime.tv_sec);
+                write32(p, stat->ctime.tv_nsec);
+        }
+}
+
+static void write_cinfo(__be32 **p, struct nfsd4_change_info *c)
+{
+        write32(p, c->atomic);
+        if (c->change_supported) {
+                write64(p, c->before_change);
+                write64(p, c->after_change);
+        } else {
+                write32(p, c->before_ctime_sec);
+                write32(p, c->before_ctime_nsec);
+                write32(p, c->after_ctime_sec);
+                write32(p, c->after_ctime_nsec);
+        }
+}
 
 #define RESERVE_SPACE(nbytes)   do {                            \
         p = resp->p;                                            \
@@ -1849,16 +1877,9 @@ nfsd4_encode_fattr(struct svc_fh *fhp, struct svc_export *exp,
                         WRITE32(NFS4_FH_PERSISTENT|NFS4_FH_VOL_RENAME);
         }
         if (bmval0 & FATTR4_WORD0_CHANGE) {
-                /*
-                 * Note: This _must_ be consistent with the scheme for writing
-                 * change_info, so any changes made here must be reflected there
-                 * as well.  (See xdr4.h:set_change_info() and the WRITECINFO()
-                 * macro above.)
-                 */
                 if ((buflen -= 8) < 0)
                         goto out_resource;
-                WRITE32(stat.ctime.tv_sec);
-                WRITE32(stat.ctime.tv_nsec);
+                write_change(&p, &stat, dentry->d_inode);
         }
         if (bmval0 & FATTR4_WORD0_SIZE) {
                 if ((buflen -= 8) < 0)
@@ -2364,7 +2385,7 @@ nfsd4_encode_create(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 
         if (!nfserr) {
                 RESERVE_SPACE(32);
-                WRITECINFO(create->cr_cinfo);
+                write_cinfo(&p, &create->cr_cinfo);
                 WRITE32(2);
                 WRITE32(create->cr_bmval[0]);
                 WRITE32(create->cr_bmval[1]);
@@ -2475,7 +2496,7 @@ nfsd4_encode_link(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_li
 
         if (!nfserr) {
                 RESERVE_SPACE(20);
-                WRITECINFO(link->li_cinfo);
+                write_cinfo(&p, &link->li_cinfo);
                 ADJUST_ARGS();
         }
         return nfserr;
@@ -2493,7 +2514,7 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
 
         nfsd4_encode_stateid(resp, &open->op_stateid);
         RESERVE_SPACE(40);
-        WRITECINFO(open->op_cinfo);
+        write_cinfo(&p, &open->op_cinfo);
         WRITE32(open->op_rflags);
         WRITE32(2);
         WRITE32(open->op_bmval[0]);
@@ -2771,7 +2792,7 @@ nfsd4_encode_remove(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 
         if (!nfserr) {
                 RESERVE_SPACE(20);
-                WRITECINFO(remove->rm_cinfo);
+                write_cinfo(&p, &remove->rm_cinfo);
                 ADJUST_ARGS();
         }
         return nfserr;
@@ -2784,8 +2805,8 @@ nfsd4_encode_rename(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_
 
         if (!nfserr) {
                 RESERVE_SPACE(40);
-                WRITECINFO(rename->rn_sinfo);
-                WRITECINFO(rename->rn_tinfo);
+                write_cinfo(&p, &rename->rn_sinfo);
+                write_cinfo(&p, &rename->rn_tinfo);
                 ADJUST_ARGS();
         }
         return nfserr;