Commit 2f437eff authored by Shiyang Ruan's avatar Shiyang Ruan Committed by Andrew Morton
Browse files

fsdax: introduce dax_lock_mapping_entry() 

The current dax_lock_page() locks dax entry by obtaining mapping and index
in page.  To support 1-to-N RMAP in NVDIMM, we need a new function to lock
a specific dax entry corresponding to this file's mapping,index.  And
output the page corresponding to the specific dax entry for caller use.

Link: https://lkml.kernel.org/r/20220603053738.1218681-5-ruansy.fnst@fujitsu.com


Signed-off-by: default avatarShiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 33a8f7f2

fs/dax.c

+63 −0
Original line number Diff line number Diff line
@@ -455,6 +455,69 @@ void dax_unlock_page(struct page *page, dax_entry_t cookie) 
	dax_unlock_entry(&xas, (void *)cookie);

}



/*

 * dax_lock_mapping_entry - Lock the DAX entry corresponding to a mapping

 * @mapping: the file's mapping whose entry we want to lock

 * @index: the offset within this file

 * @page: output the dax page corresponding to this dax entry

 *

 * Return: A cookie to pass to dax_unlock_mapping_entry() or 0 if the entry

 * could not be locked.

 */

dax_entry_t dax_lock_mapping_entry(struct address_space *mapping, pgoff_t index,

		struct page **page)

{

	XA_STATE(xas, NULL, 0);

	void *entry;



	rcu_read_lock();

	for (;;) {

		entry = NULL;

		if (!dax_mapping(mapping))

			break;



		xas.xa = &mapping->i_pages;

		xas_lock_irq(&xas);

		xas_set(&xas, index);

		entry = xas_load(&xas);

		if (dax_is_locked(entry)) {

			rcu_read_unlock();

			wait_entry_unlocked(&xas, entry);

			rcu_read_lock();

			continue;

		}

		if (!entry ||

		    dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {

			/*

			 * Because we are looking for entry from file's mapping

			 * and index, so the entry may not be inserted for now,

			 * or even a zero/empty entry.  We don't think this is

			 * an error case.  So, return a special value and do

			 * not output @page.

			 */

			entry = (void *)~0UL;

		} else {

			*page = pfn_to_page(dax_to_pfn(entry));

			dax_lock_entry(&xas, entry);

		}

		xas_unlock_irq(&xas);

		break;

	}

	rcu_read_unlock();

	return (dax_entry_t)entry;

}



void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index,

		dax_entry_t cookie)

{

	XA_STATE(xas, &mapping->i_pages, index);



	if (cookie == ~0UL)

		return;



	dax_unlock_entry(&xas, (void *)cookie);

}



/*

 * Find page cache entry at given index. If it is a DAX entry, return it

 * with the entry locked. If the page cache doesn't contain an entry at

include/linux/dax.h

+15 −0
Original line number Diff line number Diff line
@@ -161,6 +161,10 @@ struct page *dax_layout_busy_page(struct address_space *mapping); 
struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end);

dax_entry_t dax_lock_page(struct page *page);

void dax_unlock_page(struct page *page, dax_entry_t cookie);

dax_entry_t dax_lock_mapping_entry(struct address_space *mapping,

		unsigned long index, struct page **page);

void dax_unlock_mapping_entry(struct address_space *mapping,

		unsigned long index, dax_entry_t cookie);

#else

static inline struct page *dax_layout_busy_page(struct address_space *mapping)

{
@@ -188,6 +192,17 @@ static inline dax_entry_t dax_lock_page(struct page *page) 
static inline void dax_unlock_page(struct page *page, dax_entry_t cookie)

{

}



static inline dax_entry_t dax_lock_mapping_entry(struct address_space *mapping,

		unsigned long index, struct page **page)

{

	return 0;

}



static inline void dax_unlock_mapping_entry(struct address_space *mapping,

		unsigned long index, dax_entry_t cookie)

{

}

#endif



int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,