mm: page_frag: reuse existing space for 'size' and 'pfmemalloc'

Currently there is one 'struct page_frag' for every 'struct
sock' and 'struct task_struct', we are about to replace the
'struct page_f

mm: page_frag: reuse existing space for 'size' and 'pfmemalloc'

Currently there is one 'struct page_frag' for every 'struct
sock' and 'struct task_struct', we are about to replace the
'struct page_frag' with 'struct page_frag_cache' for them.
Before begin the replacing, we need to ensure the size of
'struct page_frag_cache' is not bigger than the size of
'struct page_frag', as there may be tens of thousands of
'struct sock' and 'struct task_struct' instances in the
system.

By or'ing the page order & pfmemalloc with lower bits of
'va' instead of using 'u16' or 'u32' for page size and 'u8'
for pfmemalloc, we are able to avoid 3 or 5 bytes space waste.
And page address & pfmemalloc & order is unchanged for the
same page in the same 'page_frag_cache' instance, it makes
sense to fit them together.

After this patch, the size of 'struct page_frag_cache' should be
the same as the size of 'struct page_frag'.

CC: Andrew Morton <[email protected]>
CC: Linux-MM <[email protected]>
Signed-off-by: Yunsheng Lin <[email protected]>
Reviewed-by: Alexander Duyck <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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mm: page_frag: avoid caller accessing 'page_frag_cache' directly

Use appropriate frag_page API instead of caller accessing
'page_frag_cache' directly.

CC: Andrew Morton <[email protected]>

mm: page_frag: avoid caller accessing 'page_frag_cache' directly

Use appropriate frag_page API instead of caller accessing
'page_frag_cache' directly.

CC: Andrew Morton <[email protected]>
CC: Linux-MM <[email protected]>
Signed-off-by: Yunsheng Lin <[email protected]>
Reviewed-by: Alexander Duyck <[email protected]>
Acked-by: Chuck Lever <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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mm: move the page fragment allocator from page_alloc into its own file

Inspired by [1], move the page fragment allocator from page_alloc
into its own c file and header file, as we are about to make

mm: move the page fragment allocator from page_alloc into its own file

Inspired by [1], move the page fragment allocator from page_alloc
into its own c file and header file, as we are about to make more
change for it to replace another page_frag implementation in
sock.c

As this patchset is going to replace 'struct page_frag' with
'struct page_frag_cache' in sched.h, including page_frag_cache.h
in sched.h has a compiler error caused by interdependence between
mm_types.h and mm.h for asm-offsets.c, see [2]. So avoid the compiler
error by moving 'struct page_frag_cache' to mm_types_task.h as
suggested by Alexander, see [3].

1. https://lore.kernel.org/all/[email protected]/
2. https://lore.kernel.org/all/[email protected]/
3. https://lore.kernel.org/all/CAKgT0UdH1yD=LSCXFJ=YM_aiA4OomD-2wXykO42bizaWMt_HOA@mail.gmail.com/
CC: David Howells <[email protected]>
CC: Linux-MM <[email protected]>
Signed-off-by: Yunsheng Lin <[email protected]>
Acked-by: Andrew Morton <[email protected]>
Reviewed-by: Alexander Duyck <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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