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>

4 files changed, 63 insertions, 25 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;
diff --git a/include/linux/nfsd/nfsfh.h b/include/linux/nfsd/nfsfh.h
index afa19016c4a8..8f641c908450 100644
--- a/include/linux/nfsd/nfsfh.h
+++ b/include/linux/nfsd/nfsfh.h
@@ -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;
         }
 }
diff --git a/include/linux/nfsd/xdr4.h b/include/linux/nfsd/xdr4.h
index f80d6013fdc3..d0f050f01eca 100644
--- a/include/linux/nfsd/xdr4.h
+++ b/include/linux/nfsd/xdr4.h
@@ -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 *);