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block: use DAX for partition table reads

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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: Ross Zwisler <ross.zwisler@linux.intel.com>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2016-01-28 20:25:31 -08:00
parent 9f4736fe7c
commit d1a5f2b4d8
3 changed files with 46 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

18
block/partition-generic.c
View file

@ -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;
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;
page = read_mapping_page(mapping, (pgoff_t)(n >> (PAGE_CACHE_SHIFT-9)),
NULL);
/* 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;

20
fs/dax.c
View file

@ -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

11
include/linux/dax.h
View file

@ -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);