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fix cache_lookup's documentation

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cache_lookup's documentation got dislocated by r324378. Relocate and expand
it.

Reviewed by:	jhb, kib
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Alan Somers 2019-04-10 13:02:33 +00:00
parent b65ca345ef
commit 691d4ab6f0
1 changed files with 37 additions and 18 deletions
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55
sys/kern/vfs_cache.c
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@ -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, struct componentname *cn
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 @@ cache_lookup_nomakeentry(struct vnode *dvp, struct vnode **vpp,
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)