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cache: save on branching when parsing the path by inserting a sentinel

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Tested by:	pho
This commit is contained in:
Mateusz Guzik 2020-12-28 07:33:12 +01:00 committed by Mateusz Guzik
parent 67297766b5
commit 1d6eb97677
1 changed files with 15 additions and 6 deletions
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21
sys/kern/vfs_cache.c
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@ -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);