Date: Sat, 29 May 2021 22:04:20 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: d81aefa8b7dd - main - vfs: use the sentinel trick in locked lookup path parsing Message-ID: <202105292204.14TM4Klh026235@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=d81aefa8b7dd8cbeffeda541fca9962802404983 commit d81aefa8b7dd8cbeffeda541fca9962802404983 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2021-05-25 17:34:26 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2021-05-29 22:04:09 +0000 vfs: use the sentinel trick in locked lookup path parsing --- sys/kern/vfs_lookup.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c index 5336bf87ec68..e0b98c9f5661 100644 --- a/sys/kern/vfs_lookup.c +++ b/sys/kern/vfs_lookup.c @@ -850,6 +850,7 @@ lookup(struct nameidata *ndp) { char *cp; /* pointer into pathname argument */ char *prev_ni_next; /* saved ndp->ni_next */ + char *nulchar; /* location of '\0' in cn_pnbuf */ struct vnode *dp = NULL; /* the directory we are searching */ struct vnode *tdp; /* saved dp */ struct mount *mp; /* mount table entry */ @@ -909,9 +910,23 @@ dirloop: * 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++) + nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1]; + KASSERT(*nulchar == '\0', + ("%s: expected nul at %p; string [%s]\n", __func__, nulchar, + cnp->cn_pnbuf)); + *nulchar = '/'; + for (cp = cnp->cn_nameptr; *cp != '/'; cp++) { + KASSERT(*cp != '\0', + ("%s: encountered unexpected nul; string [%s]\n", __func__, + cnp->cn_nameptr)); continue; + } + *nulchar = '\0'; cnp->cn_namelen = cp - cnp->cn_nameptr; if (cnp->cn_namelen > NAME_MAX) { error = ENAMETOOLONG;
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202105292204.14TM4Klh026235>