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LinuxKPI: add simplified vesion of page_frag_cache

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For the moment and the currently only consumer (mt76) add a simplified
version of the page_frag_cache.  We will only accept fragement sizes up
to 1 PAGE_SIZE (KASSERT) and we will always return a full page.
Should we add more consumers or small (or large) objects would become a
problem we can always add a more elaborate version.

Discussed with:	markj
Reviewed by:	markj (,hselasky commented as well)
MFC after:	3 days
Differential Revision: https://reviews.freebsd.org/D37595
This commit is contained in:
Bjoern A. Zeeb 2022-12-03 00:33:34 +00:00
parent 4b0af11437
commit 55038a6306
2 changed files with 74 additions and 0 deletions
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29
sys/compat/linuxkpi/common/include/linux/gfp.h
View File

@ -81,6 +81,11 @@
CTASSERT((__GFP_DMA32 & GFP_NATIVE_MASK) == 0);
CTASSERT((__GFP_BITS_MASK & GFP_NATIVE_MASK) == GFP_NATIVE_MASK);
struct page_frag_cache {
void *va;
int pagecnt_bias;
};
/*
* Resolve a page into a virtual address:
*
@ -95,6 +100,9 @@ extern void *linux_page_address(struct page *);
*/
extern vm_page_t linux_alloc_pages(gfp_t flags, unsigned int order);
extern void linux_free_pages(vm_page_t page, unsigned int order);
void *linuxkpi_page_frag_alloc(struct page_frag_cache *, size_t, gfp_t);
void linuxkpi_page_frag_free(void *);
void linuxkpi__page_frag_cache_drain(struct page *, size_t);
static inline struct page *
alloc_page(gfp_t flags)
@ -176,6 +184,27 @@ free_page(uintptr_t addr)
linux_free_kmem(addr, 0);
}
static inline void *
page_frag_alloc(struct page_frag_cache *pfc, size_t fragsz, gfp_t gfp)
{
return (linuxkpi_page_frag_alloc(pfc, fragsz, gfp));
}
static inline void
page_frag_free(void *addr)
{
linuxkpi_page_frag_free(addr);
}
static inline void
__page_frag_cache_drain(struct page *page, size_t count)
{
linuxkpi__page_frag_cache_drain(page, count);
}
static inline bool
gfpflags_allow_blocking(const gfp_t gfp_flags)
{

45
sys/compat/linuxkpi/common/src/linux_page.c
View File

@ -429,3 +429,48 @@ lkpi_arch_phys_wc_del(int reg)
free(mrdesc, M_LKMTRR);
#endif
}
/*
* This is a highly simplified version of the Linux page_frag_cache.
* We only support up-to 1 single page as fragment size and we will
* always return a full page. This may be wasteful on small objects
* but the only known consumer (mt76) is either asking for a half-page
* or a full page. If this was to become a problem we can implement
* a more elaborate version.
*/
void *
linuxkpi_page_frag_alloc(struct page_frag_cache *pfc,
size_t fragsz, gfp_t gfp)
{
vm_page_t pages;
if (fragsz == 0)
return (NULL);
KASSERT(fragsz <= PAGE_SIZE, ("%s: fragsz %zu > PAGE_SIZE not yet "
"supported", __func__, fragsz));
pages = alloc_pages(gfp, flsl(howmany(fragsz, PAGE_SIZE) - 1));
pfc->va = linux_page_address(pages);
/* Passed in as "count" to __page_frag_cache_drain(). Unused by us. */
pfc->pagecnt_bias = 0;
return (pfc->va);
}
void
linuxkpi_page_frag_free(void *addr)
{
vm_page_t page;
page = PHYS_TO_VM_PAGE(vtophys(addr));
linux_free_pages(page, 0);
}
void
linuxkpi__page_frag_cache_drain(struct page *page, size_t count __unused)
{
linux_free_pages(page, 0);
}