diff options
Diffstat (limited to 'fs/nfsd/nfsfh.c')
| -rw-r--r-- | fs/nfsd/nfsfh.c | 42 |
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; +} |