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filesystem-dax: Introduce dax_lock_mapping_entry()

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In preparation for implementing support for memory poison (media error)
handling via dax mappings, implement a lock_page() equivalent. Poison
error handling requires rmap and needs guarantees that the page->mapping
association is maintained / valid (inode not freed) for the duration of
the lookup.

In the device-dax case it is sufficient to simply hold a dev_pagemap
reference. In the filesystem-dax case we need to use the entry lock.

Export the entry lock via dax_lock_mapping_entry() that uses
rcu_read_lock() to protect against the inode being freed, and
revalidates the page->mapping association under xa_lock().

Cc: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
This commit is contained in:
Dan Williams 2018-07-13 21:50:16 -07:00 • committed by Dave Jiang
parent ae1139ece1
commit c2a7d2a115
2 changed files with 116 additions and 6 deletions
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13
include/linux/dax.h
View file

@ -88,6 +88,8 @@ int dax_writeback_mapping_range(struct address_space *mapping,
struct block_device *bdev, struct writeback_control *wbc);
struct page *dax_layout_busy_page(struct address_space *mapping);
bool dax_lock_mapping_entry(struct page *page);
void dax_unlock_mapping_entry(struct page *page);
#else
static inline bool bdev_dax_supported(struct block_device *bdev,
int blocksize)
@ -119,6 +121,17 @@ static inline int dax_writeback_mapping_range(struct address_space *mapping,
{
return -EOPNOTSUPP;
}
static inline bool dax_lock_mapping_entry(struct page *page)
{
if (IS_DAX(page->mapping->host))
return true;
return false;
}
static inline void dax_unlock_mapping_entry(struct page *page)
{
}
#endif
int dax_read_lock(void);