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Commit d1a5f2b4 authored by Dan Williams's avatar Dan Williams
Browse files

block: use DAX for partition table reads 



Avoid populating pagecache when the block device is in DAX mode.
Otherwise these page cache entries collide with the fsync/msync
implementation and break data durability guarantees.

Cc: Jan Kara <jack@suse.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reported-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 9f4736fe

block/partition-generic.c

+15 −3
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/kmod.h>

#include <linux/ctype.h>

#include <linux/genhd.h>

#include <linux/dax.h>

#include <linux/blktrace_api.h>



#include "partitions/check.h"
@@ -550,13 +551,24 @@ int invalidate_partitions(struct gendisk *disk, struct block_device *bdev) 
	return 0;

}



unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)

static struct page *read_pagecache_sector(struct block_device *bdev, sector_t n)

{

	struct address_space *mapping = bdev->bd_inode->i_mapping;

	struct page *page;



	page = read_mapping_page(mapping, (pgoff_t)(n >> (PAGE_CACHE_SHIFT-9)),

	return read_mapping_page(mapping, (pgoff_t)(n >> (PAGE_CACHE_SHIFT-9)),

			NULL);

}



unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)

{

	struct page *page;



	/* don't populate page cache for dax capable devices */

	if (IS_DAX(bdev->bd_inode))

		page = read_dax_sector(bdev, n);

	else

		page = read_pagecache_sector(bdev, n);



	if (!IS_ERR(page)) {

		if (PageError(page))

			goto fail;

fs/dax.c

+20 −0
Original line number Diff line number Diff line
@@ -58,6 +58,26 @@ static void dax_unmap_atomic(struct block_device *bdev, 
	blk_queue_exit(bdev->bd_queue);

}



struct page *read_dax_sector(struct block_device *bdev, sector_t n)

{

	struct page *page = alloc_pages(GFP_KERNEL, 0);

	struct blk_dax_ctl dax = {

		.size = PAGE_SIZE,

		.sector = n & ~((((int) PAGE_SIZE) / 512) - 1),

	};

	long rc;



	if (!page)

		return ERR_PTR(-ENOMEM);



	rc = dax_map_atomic(bdev, &dax);

	if (rc < 0)

		return ERR_PTR(rc);

	memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);

	dax_unmap_atomic(bdev, &dax);

	return page;

}



/*

 * dax_clear_blocks() is called from within transaction context from XFS,

 * and hence this means the stack from this point must follow GFP_NOFS

include/linux/dax.h

+11 −0
Original line number Diff line number Diff line
@@ -14,6 +14,17 @@ int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t, 
		dax_iodone_t);

int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,

		dax_iodone_t);



#ifdef CONFIG_FS_DAX

struct page *read_dax_sector(struct block_device *bdev, sector_t n);

#else

static inline struct page *read_dax_sector(struct block_device *bdev,

		sector_t n)

{

	return ERR_PTR(-ENXIO);

}

#endif



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,

				unsigned int flags, get_block_t, dax_iodone_t);