github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-26 16:12:59 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

nfsd: filecache: drop the list_lru lock during lock gc scans

Browse Source 
Under a high NFSv3 load with lots of different files being accessed,
the LRU list of garbage-collectable files can become quite long.

Asking list_lru_scan_node() to scan the whole list can result in a long
period during which a spinlock is held, blocking the addition of new LRU
items.

So ask list_lru_scan_node() to scan only a few entries at a time, and
repeat until the scan is complete.

If the shrinker runs between two consecutive calls of
list_lru_scan_node() it could invalidate the "remaining" counter which
could lead to premature freeing.  So add a spinlock to avoid that.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
NeilBrown 2025-02-18 10:39:37 -05:00 committed by Chuck Lever
parent 56221b42d7
commit fbfdc9fc0f
2 changed files with 30 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
fs/nfsd/filecache.c
View File

@ -544,6 +544,13 @@ nfsd_file_gc_cb(struct list_head *item, struct list_lru_one *lru,
return nfsd_file_lru_cb(item, lru, arg);
}
/* If the shrinker runs between calls to list_lru_walk_node() in
* nfsd_file_gc(), the "remaining" count will be wrong. This could
* result in premature freeing of some files. This may not matter much
* but is easy to fix with this spinlock which temporarily disables
* the shrinker.
*/
static DEFINE_SPINLOCK(nfsd_gc_lock);
static void
nfsd_file_gc(void)
{
@ -551,12 +558,22 @@ nfsd_file_gc(void)
LIST_HEAD(dispose);
int nid;
spin_lock(&nfsd_gc_lock);
for_each_node_state(nid, N_NORMAL_MEMORY) {
unsigned long nr = list_lru_count_node(&nfsd_file_lru, nid);
unsigned long remaining = list_lru_count_node(&nfsd_file_lru, nid);
ret += list_lru_walk_node(&nfsd_file_lru, nid, nfsd_file_gc_cb,
&dispose, &nr);
while (remaining > 0) {
unsigned long nr = min(remaining, NFSD_FILE_GC_BATCH);
remaining -= nr;
ret += list_lru_walk_node(&nfsd_file_lru, nid, nfsd_file_gc_cb,
&dispose, &nr);
if (nr)
/* walk aborted early */
remaining = 0;
}
}
spin_unlock(&nfsd_gc_lock);
trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
nfsd_file_dispose_list_delayed(&dispose);
}
@ -581,8 +598,12 @@ nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
LIST_HEAD(dispose);
unsigned long ret;
if (!spin_trylock(&nfsd_gc_lock))
return SHRINK_STOP;
ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
nfsd_file_lru_cb, &dispose);
spin_unlock(&nfsd_gc_lock);
trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
nfsd_file_dispose_list_delayed(&dispose);
return ret;

6
fs/nfsd/filecache.h
View File

@ -3,6 +3,12 @@
#include <linux/fsnotify_backend.h>
/*
* Limit the time that the list_lru_one lock is held during
* an LRU scan.
*/
#define NFSD_FILE_GC_BATCH (16UL)
/*
* This is the fsnotify_mark container that nfsd attaches to the files that it
* is holding open. Note that we have a separate refcount here aside from the