The branch main has been updated by mjg:
URL:
https://cgit.FreeBSD.org/src/commit/?id=1d6eb976774af6a84414a6785217b305021ce841
commit 1d6eb976774af6a84414a6785217b305021ce841
Author: Mateusz Guzik <mjgu...@gmail.com>
AuthorDate: 2020-12-28 06:33:12 +0000
Commit: Mateusz Guzik <m...@freebsd.org>
CommitDate: 2021-01-01 00:10:42 +0000
cache: save on branching when parsing the path by inserting a sentinel
Tested by: pho
---
sys/kern/vfs_cache.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 7f9339d2ed56..c9b0010020f8 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -4741,15 +4741,24 @@ cache_fplookup_parse(struct cache_fpl *fpl)
cnp = fpl->cnp;
/*
- * Search a new directory.
+ * Find the end of this path component, it is either / or nul.
*
- * The last component of the filename is left accessible via
- * cnp->cn_nameptr for callers that need the name. Callers needing
- * the name set the SAVENAME flag. When done, they assume
- * responsibility for freeing the pathname buffer.
+ * Store / as a temporary sentinel so that we only have one character
+ * to test for. Pathnames tend to be short so this should not be
+ * resulting in cache misses.
*/
- for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
+ KASSERT(cnp->cn_nameptr[ndp->ni_pathlen - 1] == '\0',
+ ("%s: expected nul at %p + %zu; string [%s]\n", __func__,
+ cnp->cn_nameptr, ndp->ni_pathlen - 1, cnp->cn_nameptr));
+ cnp->cn_nameptr[ndp->ni_pathlen - 1] = '/';
+ for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
+ KASSERT(*cp != '\0',
+ ("%s: encountered unexpected nul; string [%s]\n", __func__,
+ cnp->cn_nameptr));
continue;
+ }
+ cnp->cn_nameptr[ndp->ni_pathlen - 1] = '\0';
+
cnp->cn_namelen = cp - cnp->cn_nameptr;
if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
cache_fpl_smr_exit(fpl);
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