Author: mckusick
Date: Mon Aug 31 05:25:13 2020
New Revision: 364983
URL: https://svnweb.freebsd.org/changeset/base/364983
Log:
MFC of 364895
Comment on when and why pathnames are deleted from the name cache.
Modified:
stable/12/sys/kern/vfs_lookup.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/kern/vfs_lookup.c
==============================================================================
--- stable/12/sys/kern/vfs_lookup.c Mon Aug 31 01:45:48 2020
(r364982)
+++ stable/12/sys/kern/vfs_lookup.c Mon Aug 31 05:25:13 2020
(r364983)
@@ -663,6 +663,16 @@ lookup(struct nameidata *ndp)
wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
+ /*
+ * When set to zero, docache causes the last component of the
+ * pathname to be deleted from the cache and the full lookup
+ * of the name to be done (via VOP_CACHEDLOOKUP()). Often
+ * filesystems need some pre-computed values that are made
+ * during the full lookup, for instance UFS sets dp->i_offset.
+ *
+ * The docache variable is set to zero when requested by the
+ * NOCACHE flag and for all modifying operations except CREATE.
+ */
docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
if (cnp->cn_nameiop == DELETE ||
(wantparent && cnp->cn_nameiop != CREATE &&
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