On Tue, 11 Feb 2025 12:52:11 -0500 Steven Rostedt <rost...@goodmis.org> wrote:
> On Tue, 11 Feb 2025 23:47:03 +0900 > "Masami Hiramatsu (Google)" <mhira...@kernel.org> wrote: > > > From: Masami Hiramatsu (Google) <mhira...@kernel.org> > > > > Add reserve_mem_release_by_name() to release a reserved memory region > > with a given name. This allows us to release reserved memory which is > > defined by kernel cmdline, after boot. > > > > Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org> > > Cc: Andrew Morton <a...@linux-foundation.org> > > Cc: Mike Rapoport <r...@kernel.org> > > Cc: linux...@kvack.org > > Hi, can we get one of the Memory Management maintainers to ack this patch? > > We will be having devices going out with the reserve_mem option to perform > tracing in the field. But that only happens if the user grants permission > to do so. But the kernel command line does not change between users that > granted permission and those that do not. We would like to free up the > memory for those devices where the users did not grant permission to trace, > as then the memory is just wasted. Thanks Steve for explaining, I missed Ccing the background information. Here is the covermail of this series. https://lore.kernel.org/all/173928521419.906035.17750338150436695675.stgit@devnote2/ Thank you, > > Thanks! > > -- Steve > > > > --- > > Changes in v2: > > - Rename reserved_mem_* to reserve_mem_*. > > --- > > include/linux/mm.h | 1 + > > mm/memblock.c | 72 > > +++++++++++++++++++++++++++++++++++++++++++--------- > > 2 files changed, 61 insertions(+), 12 deletions(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index f02925447e59..fe5f7711df04 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -4197,6 +4197,7 @@ void vma_pgtable_walk_begin(struct vm_area_struct > > *vma); > > void vma_pgtable_walk_end(struct vm_area_struct *vma); > > > > int reserve_mem_find_by_name(const char *name, phys_addr_t *start, > > phys_addr_t *size); > > +int reserve_mem_release_by_name(const char *name); > > > > #ifdef CONFIG_64BIT > > int do_mseal(unsigned long start, size_t len_in, unsigned long flags); > > diff --git a/mm/memblock.c b/mm/memblock.c > > index 095c18b5c430..c8d207ebb93c 100644 > > --- a/mm/memblock.c > > +++ b/mm/memblock.c > > @@ -16,6 +16,7 @@ > > #include <linux/kmemleak.h> > > #include <linux/seq_file.h> > > #include <linux/memblock.h> > > +#include <linux/mutex.h> > > > > #include <asm/sections.h> > > #include <linux/io.h> > > @@ -2263,6 +2264,7 @@ struct reserve_mem_table { > > }; > > static struct reserve_mem_table > > reserved_mem_table[RESERVE_MEM_MAX_ENTRIES]; > > static int reserved_mem_count; > > +static DEFINE_MUTEX(reserve_mem_lock); > > > > /* Add wildcard region with a lookup name */ > > static void __init reserved_mem_add(phys_addr_t start, phys_addr_t size, > > @@ -2276,6 +2278,21 @@ static void __init reserved_mem_add(phys_addr_t > > start, phys_addr_t size, > > strscpy(map->name, name); > > } > > > > +static struct reserve_mem_table *reserve_mem_find_by_name_nolock(const > > char *name) > > +{ > > + struct reserve_mem_table *map; > > + int i; > > + > > + for (i = 0; i < reserved_mem_count; i++) { > > + map = &reserved_mem_table[i]; > > + if (!map->size) > > + continue; > > + if (strcmp(name, map->name) == 0) > > + return map; > > + } > > + return NULL; > > +} > > + > > /** > > * reserve_mem_find_by_name - Find reserved memory region with a given name > > * @name: The name that is attached to a reserved memory region > > @@ -2289,22 +2306,53 @@ static void __init reserved_mem_add(phys_addr_t > > start, phys_addr_t size, > > int reserve_mem_find_by_name(const char *name, phys_addr_t *start, > > phys_addr_t *size) > > { > > struct reserve_mem_table *map; > > - int i; > > > > - for (i = 0; i < reserved_mem_count; i++) { > > - map = &reserved_mem_table[i]; > > - if (!map->size) > > - continue; > > - if (strcmp(name, map->name) == 0) { > > - *start = map->start; > > - *size = map->size; > > - return 1; > > - } > > - } > > - return 0; > > + guard(mutex)(&reserve_mem_lock); > > + map = reserve_mem_find_by_name_nolock(name); > > + if (!map) > > + return 0; > > + > > + *start = map->start; > > + *size = map->size; > > + return 1; > > } > > EXPORT_SYMBOL_GPL(reserve_mem_find_by_name); > > > > +/** > > + * reserve_mem_release_by_name - Release reserved memory region with a > > given name > > + * @name: The name that is attatched to a reserved memory region > > + * > > + * Forcibly release the pages in the reserved memory region so that those > > memory > > + * can be used as free memory. After released the reserved region size > > becomes 0. > > + * > > + * Returns: 1 if released or 0 if not found. > > + */ > > +int reserve_mem_release_by_name(const char *name) > > +{ > > + struct reserve_mem_table *map; > > + unsigned int page_count; > > + phys_addr_t start; > > + > > + guard(mutex)(&reserve_mem_lock); > > + map = reserve_mem_find_by_name_nolock(name); > > + if (!map) > > + return 0; > > + > > + start = map->start; > > + page_count = DIV_ROUND_UP(map->size, PAGE_SIZE); > > + > > + for (int i = 0; i < page_count; i++) { > > + phys_addr_t addr = start + i * PAGE_SIZE; > > + struct page *page = pfn_to_page(addr >> PAGE_SHIFT); > > + > > + page->flags &= ~BIT(PG_reserved); > > + __free_page(page); > > + } > > + map->size = 0; > > + > > + return 1; > > +} > > + > > /* > > * Parse reserve_mem=nn:align:name > > */ > -- Masami Hiramatsu (Google) <mhira...@kernel.org>
