Commit 18022c5d authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm: add get_kernel_page[s] for pinning of kernel addresses for I/O 



This patch adds two new APIs get_kernel_pages() and get_kernel_page() that
may be used to pin a vector of kernel addresses for IO.  The initial user
is expected to be NFS for allowing pages to be written to swap using
aops->direct_IO().  Strictly speaking, swap-over-NFS only needs to pin one
page for IO but it makes sense to express the API in terms of a vector and
add a helper for pinning single pages.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Cc: Mark Salter <msalter@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f981c595

include/linux/blk_types.h

+2 −0
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ enum rq_flag_bits { 
	__REQ_FLUSH_SEQ,	/* request for flush sequence */

	__REQ_IO_STAT,		/* account I/O stat */

	__REQ_MIXED_MERGE,	/* merge of different types, fail separately */

	__REQ_KERNEL, 		/* direct IO to kernel pages */

	__REQ_NR_BITS,		/* stops here */

};
@@ -201,5 +202,6 @@ enum rq_flag_bits { 
#define REQ_IO_STAT		(1 << __REQ_IO_STAT)

#define REQ_MIXED_MERGE		(1 << __REQ_MIXED_MERGE)

#define REQ_SECURE		(1 << __REQ_SECURE)

#define REQ_KERNEL		(1 << __REQ_KERNEL)



#endif /* __LINUX_BLK_TYPES_H */

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -165,6 +165,8 @@ struct inodes_stat_t { 
#define READ			0

#define WRITE			RW_MASK

#define READA			RWA_MASK

#define KERNEL_READ		(READ|REQ_KERNEL)

#define KERNEL_WRITE		(WRITE|REQ_KERNEL)



#define READ_SYNC		(READ | REQ_SYNC)

#define WRITE_SYNC		(WRITE | REQ_SYNC | REQ_NOIDLE)

include/linux/mm.h

+4 −0
Original line number Diff line number Diff line
@@ -1019,6 +1019,10 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
			struct page **pages, struct vm_area_struct **vmas);

int get_user_pages_fast(unsigned long start, int nr_pages, int write,

			struct page **pages);

struct kvec;

int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,

			struct page **pages);

int get_kernel_page(unsigned long start, int write, struct page **pages);

struct page *get_dump_page(unsigned long addr);



extern int try_to_release_page(struct page * page, gfp_t gfp_mask);

mm/swap.c

+53 −0
Original line number Diff line number Diff line
@@ -236,6 +236,59 @@ void put_pages_list(struct list_head *pages) 
}

EXPORT_SYMBOL(put_pages_list);



/*

 * get_kernel_pages() - pin kernel pages in memory

 * @kiov:	An array of struct kvec structures

 * @nr_segs:	number of segments to pin

 * @write:	pinning for read/write, currently ignored

 * @pages:	array that receives pointers to the pages pinned.

 *		Should be at least nr_segs long.

 *

 * Returns number of pages pinned. This may be fewer than the number

 * requested. If nr_pages is 0 or negative, returns 0. If no pages

 * were pinned, returns -errno. Each page returned must be released

 * with a put_page() call when it is finished with.

 */

int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,

		struct page **pages)

{

	int seg;



	for (seg = 0; seg < nr_segs; seg++) {

		if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))

			return seg;



		/* virt_to_page sanity checks the PFN */

		pages[seg] = virt_to_page(kiov[seg].iov_base);

		page_cache_get(pages[seg]);

	}



	return seg;

}

EXPORT_SYMBOL_GPL(get_kernel_pages);



/*

 * get_kernel_page() - pin a kernel page in memory

 * @start:	starting kernel address

 * @write:	pinning for read/write, currently ignored

 * @pages:	array that receives pointer to the page pinned.

 *		Must be at least nr_segs long.

 *

 * Returns 1 if page is pinned. If the page was not pinned, returns

 * -errno. The page returned must be released with a put_page() call

 * when it is finished with.

 */

int get_kernel_page(unsigned long start, int write, struct page **pages)

{

	const struct kvec kiov = {

		.iov_base = (void *)start,

		.iov_len = PAGE_SIZE

	};



	return get_kernel_pages(&kiov, 1, write, pages);

}

EXPORT_SYMBOL_GPL(get_kernel_page);



static void pagevec_lru_move_fn(struct pagevec *pvec,

	void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),

	void *arg)

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