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-rw-r--r--fs/nfsd/nfsfh.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 8c52b6c9d31a..76ea268dc420 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -628,6 +628,10 @@ void fh_fill_pre_attrs(struct svc_fh *fhp)
stat.mtime = inode->i_mtime;
stat.ctime = inode->i_ctime;
stat.size = inode->i_size;
+ if (v4 && IS_I_VERSION(inode)) {
+ stat.change_cookie = inode_query_iversion(inode);
+ stat.result_mask |= STATX_CHANGE_COOKIE;
+ }
}
if (v4)
fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
@@ -659,6 +663,10 @@ void fh_fill_post_attrs(struct svc_fh *fhp)
if (err) {
fhp->fh_post_saved = false;
fhp->fh_post_attr.ctime = inode->i_ctime;
+ if (v4 && IS_I_VERSION(inode)) {
+ fhp->fh_post_attr.change_cookie = inode_query_iversion(inode);
+ fhp->fh_post_attr.result_mask |= STATX_CHANGE_COOKIE;
+ }
} else
fhp->fh_post_saved = true;
if (v4)
@@ -748,3 +756,37 @@ enum fsid_source fsid_source(const struct svc_fh *fhp)
return FSIDSOURCE_UUID;
return FSIDSOURCE_DEV;
}
+
+/*
+ * We could use i_version alone as the change attribute. However, i_version
+ * can go backwards on a regular file after an unclean shutdown. On its own
+ * that doesn't necessarily cause a problem, but if i_version goes backwards
+ * and then is incremented again it could reuse a value that was previously
+ * used before boot, and a client who queried the two values might incorrectly
+ * assume nothing changed.
+ *
+ * By using both ctime and the i_version counter we guarantee that as long as
+ * time doesn't go backwards we never reuse an old value. If the filesystem
+ * advertises STATX_ATTR_CHANGE_MONOTONIC, then this mitigation is not
+ * needed.
+ *
+ * We only need to do this for regular files as well. For directories, we
+ * assume that the new change attr is always logged to stable storage in some
+ * fashion before the results can be seen.
+ */
+u64 nfsd4_change_attribute(struct kstat *stat, struct inode *inode)
+{
+ u64 chattr;
+
+ if (stat->result_mask & STATX_CHANGE_COOKIE) {
+ chattr = stat->change_cookie;
+ if (S_ISREG(inode->i_mode) &&
+ !(stat->attributes & STATX_ATTR_CHANGE_MONOTONIC)) {
+ chattr += (u64)stat->ctime.tv_sec << 30;
+ chattr += stat->ctime.tv_nsec;
+ }
+ } else {
+ chattr = time_to_chattr(&stat->ctime);
+ }
+ return chattr;
+}