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fsdax: introduce dax_lock_mapping_entry()

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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: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shiyang Ruan 2022-06-03 13:37:28 +08:00 committed by akpm
parent 33a8f7f2b3
commit 2f437effc6
2 changed files with 78 additions and 0 deletions
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63
fs/dax.c
View file

@ -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

15
include/linux/dax.h
View file

@ -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,