Commit 5a178119 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm: add support for direct_IO to highmem pages 



The patch "mm: add support for a filesystem to activate swap files and use
direct_IO for writing swap pages" added support for using direct_IO to
write swap pages but it is insufficient for highmem pages.

To support highmem pages, this patch kmaps() the page before calling the
direct_IO() handler.  As direct_IO deals with virtual addresses an
additional helper is necessary for get_kernel_pages() to lookup the struct
page for a kmap virtual address.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Acked-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>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a509bc1a

include/linux/highmem.h

+7 −0
Original line number Diff line number Diff line
@@ -39,10 +39,17 @@ extern unsigned long totalhigh_pages; 


void kmap_flush_unused(void);



struct page *kmap_to_page(void *addr);



#else /* CONFIG_HIGHMEM */



static inline unsigned int nr_free_highpages(void) { return 0; }



static inline struct page *kmap_to_page(void *addr)

{

	return virt_to_page(addr);

}



#define totalhigh_pages 0UL



#ifndef ARCH_HAS_KMAP

mm/highmem.c

+12 −0
Original line number Diff line number Diff line
@@ -94,6 +94,18 @@ static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); 
		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)

#endif



struct page *kmap_to_page(void *vaddr)

{

	unsigned long addr = (unsigned long)vaddr;



	if (addr >= PKMAP_ADDR(0) && addr <= PKMAP_ADDR(LAST_PKMAP)) {

		int i = (addr - PKMAP_ADDR(0)) >> PAGE_SHIFT;

		return pte_page(pkmap_page_table[i]);

	}



	return virt_to_page(addr);

}



static void flush_all_zero_pkmaps(void)

{

	int i;

mm/page_io.c

+2 −1
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) 
		struct file *swap_file = sis->swap_file;

		struct address_space *mapping = swap_file->f_mapping;

		struct iovec iov = {

			.iov_base = page_address(page),

			.iov_base = kmap(page),

			.iov_len  = PAGE_SIZE,

		};
@@ -218,6 +218,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) 
		ret = mapping->a_ops->direct_IO(KERNEL_WRITE,

						&kiocb, &iov,

						kiocb.ki_pos, 1);

		kunmap(page);

		if (ret == PAGE_SIZE) {

			count_vm_event(PSWPOUT);

			ret = 0;

mm/swap.c

+1 −2
Original line number Diff line number Diff line
@@ -258,8 +258,7 @@ int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write, 
		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);

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

		page_cache_get(pages[seg]);

	}

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