diff options
| author | Christoph Hellwig <hch@lst.de> | 2017-12-29 08:54:01 +0100 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2018-01-08 11:46:23 -0800 |
| commit | 832d7aa051106c927cae05ced29d3fd31459ed21 (patch) | |
| tree | 72b34c8b3ae395aedaf444246073791ab20ea3c1 /kernel/memremap.c | |
| parent | 0822acb86cf340cd45b3af6436cec7e3bb24ebd2 (diff) | |
| download | lwn-832d7aa051106c927cae05ced29d3fd31459ed21.tar.gz lwn-832d7aa051106c927cae05ced29d3fd31459ed21.zip | |
mm: optimize dev_pagemap reference counting around get_dev_pagemap
Change the calling convention so that get_dev_pagemap always consumes the
previous reference instead of doing this using an explicit earlier call to
put_dev_pagemap in the callers.
The callers will still need to put the final reference after finishing the
loop over the pages.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'kernel/memremap.c')
| -rw-r--r-- | kernel/memremap.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/kernel/memremap.c b/kernel/memremap.c index 3df6cd4ffb40..891c77487a6a 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -507,22 +507,23 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) * @pfn: page frame number to lookup page_map * @pgmap: optional known pgmap that already has a reference * - * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the - * same mapping. + * If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap + * is non-NULL but does not cover @pfn the reference to it will be released. */ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, struct dev_pagemap *pgmap) { - const struct resource *res = pgmap ? pgmap->res : NULL; resource_size_t phys = PFN_PHYS(pfn); /* - * In the cached case we're already holding a live reference so - * we can simply do a blind increment + * In the cached case we're already holding a live reference. */ - if (res && phys >= res->start && phys <= res->end) { - percpu_ref_get(pgmap->ref); - return pgmap; + if (pgmap) { + const struct resource *res = pgmap ? pgmap->res : NULL; + + if (res && phys >= res->start && phys <= res->end) + return pgmap; + put_dev_pagemap(pgmap); } /* fall back to slow path lookup */ |