On Fri, Jan 16, 2009 at 12:43 PM, Ian Kent <[email protected]> wrote:
> > > If we can simply flag the cached version as stale, then lazy reloads
> > > > should be possible.
> > >
> > > Maybe not.
> > >
> > > The layer of code above the lookup modules does the re-loads but it is
> > > general wrt. the map type so for a "nobrowse" map it won't read the
> map.
> > > I'm not sure yet that putting special case exceptions in that code is a
> > > good thing to do or even straight forward. But, for the large map case,
> >
> > Or maybe I'm talking nonsense as it looks like I've actually got plenty
> > of map type context in the layer above, hehe.
> >
> > > we can consider reading the entire map an expensive operation, so if we
> > > did change the layer above and we found the map needed to be modified
> > > then marked the map as stale we would need to scan the file map for the
> > > key (as the map is out of date) and then read the whole map later. That
> > > means we would end up reading the map at least one and a half times (on
> > > average) instead of once (assuming no lookups between marking the map
> > > stale and re-reading).
> > >
> > > I'm tending toward reading the map during the lookup so the map is up
> to
> > > date when we look for the key in the cache.
>
> Or maybe not.
>
> If we take advantage of the existing code to mark the map as stale and
> handle the re-read and we accept the overhead of scanning the file map
> while waiting for the update something like this could be all that's
> needed.
>
> autofs-5.0.4 - always read file maps
>
> From: Ian Kent <[email protected]>
>
>
> ---
>
> daemon/lookup.c | 9 ++++++---
> modules/lookup_file.c | 11 ++++++++++-
> 2 files changed, 16 insertions(+), 4 deletions(-)
>
>
> diff --git a/daemon/lookup.c b/daemon/lookup.c
> index 741d846..b954045 100644
> --- a/daemon/lookup.c
> +++ b/daemon/lookup.c
> @@ -283,10 +283,13 @@ static int do_read_map(struct autofs_point *ap,
> struct map_source *map, time_t a
> * for the fail cases to function correctly and to cache the
> * lookup handle.
> *
> - * We always need to whole map for direct mounts in order to
> - * mount the triggers.
> + * We always need to read the whole map for direct mounts in
> + * order to mount the triggers. We also want to read the whole
> + * map if it's a file map to avoid potentially lengthy linear
> + * file scanning.
> */
> - if (!(ap->flags & MOUNT_FLAG_GHOST) && ap->type != LKP_DIRECT)
> + if (strcmp(map->type, "file") ||
I suspect that you want && instead.
+ (!(ap->flags & MOUNT_FLAG_GHOST) && ap->type != LKP_DIRECT))
> return NSS_STATUS_SUCCESS;
>
> if (!map->stale)
> diff --git a/modules/lookup_file.c b/modules/lookup_file.c
> index 95b9f6f..9a1c39b 100644
> --- a/modules/lookup_file.c
> +++ b/modules/lookup_file.c
> @@ -93,7 +93,6 @@ int lookup_init(const char *mapfmt, int argc, const char
> *const *argv, void **co
> argv[0]);
> return 1;
> }
> -
> ctxt->mtime = st.st_mtime;
>
> if (!mapfmt)
> @@ -1064,7 +1063,16 @@ int lookup_mount(struct autofs_point *ap, const char
> *name, int name_len, void *
> if (ap->type == LKP_INDIRECT && *key != '/') {
> char *lkp_key;
>
> + /*
> + * We can skip the map lookup and cache update altogether
> + * if we know the map hasn't been modified since it was
> + * last read.
> + */
> cache_readlock(mc);
> + me = cache_lookup_first(mc);
> + if (me && ctxt->mtime <= me->age)
You have to call stat(2) or fstat(2) at some point or else ctxt->mtime will
never change.
+ goto do_lookup;
My brain is bleeding.
+
> me = cache_lookup_distinct(mc, key);
> if (me && me->multi)
> lkp_key = strdup(me->multi->key);
> @@ -1088,6 +1096,7 @@ int lookup_mount(struct autofs_point *ap, const char
> *name, int name_len, void *
> }
>
> cache_readlock(mc);
> +do_lookup:
> me = cache_lookup(mc, key);
> /* Stale mapent => check for entry in alternate source or wildcard
> */
> if (me && !me->mapent) {
>
>
>
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