NFS: Use information about the change attribute to optimise updates
If the NFSv4.2 server supports the 'change_attr_type' attribute, then allow the client to optimise its attribute cache update strategy. Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust
parent
7f08a3359a
commit
6f9be83d07
111
fs/nfs/inode.c
111
fs/nfs/inode.c
@ -1657,25 +1657,20 @@ EXPORT_SYMBOL_GPL(_nfs_display_fhandle);
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#endif
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/**
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* nfs_inode_attrs_need_update - check if the inode attributes need updating
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* @inode: pointer to inode
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* nfs_inode_attrs_cmp_generic - compare attributes
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* @fattr: attributes
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* @inode: pointer to inode
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*
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* Attempt to divine whether or not an RPC call reply carrying stale
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* attributes got scheduled after another call carrying updated ones.
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*
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* To do so, the function first assumes that a more recent ctime means
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* that the attributes in fattr are newer, however it also attempt to
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* catch the case where ctime either didn't change, or went backwards
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* (if someone reset the clock on the server) by looking at whether
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* or not this RPC call was started after the inode was last updated.
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* Note also the check for wraparound of 'attr_gencount'
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*
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* The function returns 'true' if it thinks the attributes in 'fattr' are
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* more recent than the ones cached in the inode.
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*
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* The function returns '1' if it thinks the attributes in @fattr are
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* more recent than the ones cached in @inode. Otherwise it returns
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* the value '0'.
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*/
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static int nfs_inode_attrs_need_update(const struct inode *inode, const struct nfs_fattr *fattr)
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static int nfs_inode_attrs_cmp_generic(const struct nfs_fattr *fattr,
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const struct inode *inode)
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{
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unsigned long attr_gencount = NFS_I(inode)->attr_gencount;
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@ -1683,15 +1678,93 @@ static int nfs_inode_attrs_need_update(const struct inode *inode, const struct n
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(long)(attr_gencount - nfs_read_attr_generation_counter()) > 0;
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}
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static int nfs_refresh_inode_locked(struct inode *inode, struct nfs_fattr *fattr)
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/**
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* nfs_inode_attrs_cmp_monotonic - compare attributes
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* @fattr: attributes
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* @inode: pointer to inode
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*
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* Attempt to divine whether or not an RPC call reply carrying stale
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* attributes got scheduled after another call carrying updated ones.
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*
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* We assume that the server observes monotonic semantics for
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* the change attribute, so a larger value means that the attributes in
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* @fattr are more recent, in which case the function returns the
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* value '1'.
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* A return value of '0' indicates no measurable change
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* A return value of '-1' means that the attributes in @inode are
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* more recent.
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*/
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static int nfs_inode_attrs_cmp_monotonic(const struct nfs_fattr *fattr,
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const struct inode *inode)
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{
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int ret;
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s64 diff = fattr->change_attr - inode_peek_iversion_raw(inode);
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if (diff > 0)
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return 1;
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return diff == 0 ? 0 : -1;
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}
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/**
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* nfs_inode_attrs_cmp_strict_monotonic - compare attributes
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* @fattr: attributes
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* @inode: pointer to inode
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*
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* Attempt to divine whether or not an RPC call reply carrying stale
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* attributes got scheduled after another call carrying updated ones.
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*
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* We assume that the server observes strictly monotonic semantics for
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* the change attribute, so a larger value means that the attributes in
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* @fattr are more recent, in which case the function returns the
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* value '1'.
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* A return value of '-1' means that the attributes in @inode are
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* more recent or unchanged.
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*/
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static int nfs_inode_attrs_cmp_strict_monotonic(const struct nfs_fattr *fattr,
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const struct inode *inode)
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{
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return nfs_inode_attrs_cmp_monotonic(fattr, inode) > 0 ? 1 : -1;
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}
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/**
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* nfs_inode_attrs_cmp - compare attributes
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* @fattr: attributes
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* @inode: pointer to inode
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*
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* This function returns '1' if it thinks the attributes in @fattr are
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* more recent than the ones cached in @inode. It returns '-1' if
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* the attributes in @inode are more recent than the ones in @fattr,
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* and it returns 0 if not sure.
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*/
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static int nfs_inode_attrs_cmp(const struct nfs_fattr *fattr,
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const struct inode *inode)
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{
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if (nfs_inode_attrs_cmp_generic(fattr, inode) > 0)
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return 1;
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switch (NFS_SERVER(inode)->change_attr_type) {
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case NFS4_CHANGE_TYPE_IS_UNDEFINED:
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break;
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case NFS4_CHANGE_TYPE_IS_TIME_METADATA:
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if (!(fattr->valid & NFS_ATTR_FATTR_CHANGE))
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break;
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return nfs_inode_attrs_cmp_monotonic(fattr, inode);
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default:
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if (!(fattr->valid & NFS_ATTR_FATTR_CHANGE))
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break;
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return nfs_inode_attrs_cmp_strict_monotonic(fattr, inode);
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}
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return 0;
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}
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static int nfs_refresh_inode_locked(struct inode *inode,
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struct nfs_fattr *fattr)
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{
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int attr_cmp = nfs_inode_attrs_cmp(fattr, inode);
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int ret = 0;
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trace_nfs_refresh_inode_enter(inode);
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if (nfs_inode_attrs_need_update(inode, fattr))
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if (attr_cmp > 0)
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ret = nfs_update_inode(inode, fattr);
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else
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else if (attr_cmp == 0)
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ret = nfs_check_inode_attributes(inode, fattr);
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trace_nfs_refresh_inode_exit(inode, ret);
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@ -1776,11 +1849,13 @@ EXPORT_SYMBOL_GPL(nfs_post_op_update_inode);
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*/
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int nfs_post_op_update_inode_force_wcc_locked(struct inode *inode, struct nfs_fattr *fattr)
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{
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int attr_cmp = nfs_inode_attrs_cmp(fattr, inode);
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int status;
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/* Don't do a WCC update if these attributes are already stale */
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if ((fattr->valid & NFS_ATTR_FATTR) == 0 ||
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!nfs_inode_attrs_need_update(inode, fattr)) {
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if (attr_cmp < 0)
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return 0;
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if ((fattr->valid & NFS_ATTR_FATTR) == 0 || !attr_cmp) {
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fattr->valid &= ~(NFS_ATTR_FATTR_PRECHANGE
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| NFS_ATTR_FATTR_PRESIZE
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| NFS_ATTR_FATTR_PREMTIME
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@ -1186,10 +1186,23 @@ nfs4_update_changeattr_locked(struct inode *inode,
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unsigned long timestamp, unsigned long cache_validity)
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{
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struct nfs_inode *nfsi = NFS_I(inode);
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u64 change_attr = inode_peek_iversion_raw(inode);
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cache_validity |= NFS_INO_INVALID_CTIME | NFS_INO_INVALID_MTIME;
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if (cinfo->atomic && cinfo->before == inode_peek_iversion_raw(inode)) {
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switch (NFS_SERVER(inode)->change_attr_type) {
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case NFS4_CHANGE_TYPE_IS_UNDEFINED:
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break;
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case NFS4_CHANGE_TYPE_IS_TIME_METADATA:
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if ((s64)(change_attr - cinfo->after) > 0)
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goto out;
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break;
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default:
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if ((s64)(change_attr - cinfo->after) >= 0)
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goto out;
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}
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if (cinfo->atomic && cinfo->before == change_attr) {
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nfsi->attrtimeo_timestamp = jiffies;
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} else {
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if (S_ISDIR(inode->i_mode)) {
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@ -1201,7 +1214,7 @@ nfs4_update_changeattr_locked(struct inode *inode,
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cache_validity |= NFS_INO_REVAL_PAGECACHE;
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}
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if (cinfo->before != inode_peek_iversion_raw(inode))
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if (cinfo->before != change_attr)
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cache_validity |= NFS_INO_INVALID_ACCESS |
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NFS_INO_INVALID_ACL |
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NFS_INO_INVALID_XATTR;
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@ -1209,8 +1222,9 @@ nfs4_update_changeattr_locked(struct inode *inode,
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inode_set_iversion_raw(inode, cinfo->after);
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nfsi->read_cache_jiffies = timestamp;
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nfsi->attr_gencount = nfs_inc_attr_generation_counter();
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nfs_set_cache_invalid(inode, cache_validity);
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nfsi->cache_validity &= ~NFS_INO_INVALID_CHANGE;
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out:
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nfs_set_cache_invalid(inode, cache_validity);
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}
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void
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