Date: Fri, 31 May 2019 16:22:29 +0000 (UTC) From: Alan Somers <asomers@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r348463 - stable/12/sys/kern Message-ID: <201905311622.x4VGMT5q023731@repo.freebsd.org>
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Author: asomers Date: Fri May 31 16:22:29 2019 New Revision: 348463 URL: https://svnweb.freebsd.org/changeset/base/348463 Log: MFC r346078: fix cache_lookup's documentation cache_lookup's documentation got dislocated by r324378. Relocate and expand it. Reviewed by: jhb, kib Sponsored by: The FreeBSD Foundation Modified: stable/12/sys/kern/vfs_cache.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/vfs_cache.c ============================================================================== --- stable/12/sys/kern/vfs_cache.c Fri May 31 16:21:38 2019 (r348462) +++ stable/12/sys/kern/vfs_cache.c Fri May 31 16:22:29 2019 (r348463) @@ -150,7 +150,7 @@ struct namecache_ts { * Names found by directory scans are retained in a cache * for future reference. It is managed LRU, so frequently * used names will hang around. Cache is indexed by hash value - * obtained from (vp, name) where vp refers to the directory + * obtained from (dvp, name) where dvp refers to the directory * containing name. * * If it is a "negative" entry, (i.e. for a name that is known NOT to @@ -1129,23 +1129,6 @@ cache_lookup_dot(struct vnode *dvp, struct vnode **vpp return (-1); } -/* - * Lookup an entry in the cache - * - * Lookup is called with dvp pointing to the directory to search, - * cnp pointing to the name of the entry being sought. If the lookup - * succeeds, the vnode is returned in *vpp, and a status of -1 is - * returned. If the lookup determines that the name does not exist - * (negative caching), a status of ENOENT is returned. If the lookup - * fails, a status of zero is returned. If the directory vnode is - * recycled out from under us due to a forced unmount, a status of - * ENOENT is returned. - * - * vpp is locked and ref'd on return. If we're looking up DOTDOT, dvp is - * unlocked. If we're looking up . an extra ref is taken, but the lock is - * not recursively acquired. - */ - static __noinline int cache_lookup_nomakeentry(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, struct timespec *tsp, int *ticksp) @@ -1229,6 +1212,42 @@ out_no_entry: return (0); } +/** + * Lookup a name in the name cache + * + * # Arguments + * + * - dvp: Parent directory in which to search. + * - vpp: Return argument. Will contain desired vnode on cache hit. + * - cnp: Parameters of the name search. The most interesting bits of + * the cn_flags field have the following meanings: + * - MAKEENTRY: If clear, free an entry from the cache rather than look + * it up. + * - ISDOTDOT: Must be set if and only if cn_nameptr == ".." + * - tsp: Return storage for cache timestamp. On a successful (positive + * or negative) lookup, tsp will be filled with any timespec that + * was stored when this cache entry was created. However, it will + * be clear for "." entries. + * - ticks: Return storage for alternate cache timestamp. On a successful + * (positive or negative) lookup, it will contain the ticks value + * that was current when the cache entry was created, unless cnp + * was ".". + * + * # Returns + * + * - -1: A positive cache hit. vpp will contain the desired vnode. + * - ENOENT: A negative cache hit, or dvp was recycled out from under us due + * to a forced unmount. vpp will not be modified. If the entry + * is a whiteout, then the ISWHITEOUT flag will be set in + * cnp->cn_flags. + * - 0: A cache miss. vpp will not be modified. + * + * # Locking + * + * On a cache hit, vpp will be returned locked and ref'd. If we're looking up + * .., dvp is unlocked. If we're looking up . an extra ref is taken, but the + * lock is not recursively acquired. + */ int cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, struct timespec *tsp, int *ticksp)
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