| Message ID | 20220419045045.1664996-5-ruansy.fnst@fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fsdax: introduce fs query to support reflink | expand |
On Tue, Apr 19, 2022 at 12:50:42PM +0800, Shiyang Ruan wrote: > 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. > > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> > Reviewed-by: Christoph Hellwig <hch@lst.de> > --- > fs/dax.c | 63 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/dax.h | 15 +++++++++++ > 2 files changed, 78 insertions(+) > > diff --git a/fs/dax.c b/fs/dax.c > index 1ac12e877f4f..57efd3f73655 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -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; In this case we exit to the caller with the magic return value, having not set *page. Either the comment for this function should note that the caller must set *page to a known value (NULL?) before the call, or we should set *page = NULL here. AFAICT the callers in this series initialize page to NULL before passing in &page, so I think the comment update would be fine. With the **page requirement documented, Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D > + } 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 > diff --git a/include/linux/dax.h b/include/linux/dax.h > index 9c426a207ba8..c152f315d1c9 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -143,6 +143,10 @@ 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) > { > @@ -170,6 +174,17 @@ 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, > -- > 2.35.1 > > >
diff --git a/fs/dax.c b/fs/dax.c index 1ac12e877f4f..57efd3f73655 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -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 diff --git a/include/linux/dax.h b/include/linux/dax.h index 9c426a207ba8..c152f315d1c9 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -143,6 +143,10 @@ 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) { @@ -170,6 +174,17 @@ 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,