Date: Fri, 1 Jan 2021 00:11:53 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 1d6eb976774a - main - cache: save on branching when parsing the path by inserting a sentinel Message-ID: <202101010011.1010BrGn005857@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=1d6eb976774af6a84414a6785217b305021ce841 commit 1d6eb976774af6a84414a6785217b305021ce841 Author: Mateusz Guzik <mjguzik@gmail.com> AuthorDate: 2020-12-28 06:33:12 +0000 Commit: Mateusz Guzik <mjg@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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