| Message ID | 20210924130959.2695749-6-ruansy.fnst@fujitsu.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fsdax: introduce fs query to support reflink | expand |
On Fri, Sep 24, 2021 at 09:09:56PM +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 BTW, output the page corresponding to the specific dax entry for > caller use. > > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> > --- > fs/dax.c | 65 ++++++++++++++++++++++++++++++++++++++++++++- > include/linux/dax.h | 15 +++++++++++ > 2 files changed, 79 insertions(+), 1 deletion(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 798c43f09eee..509b65e60478 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -390,7 +390,7 @@ static struct page *dax_busy_page(void *entry) > } > > /* > - * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page > + * dax_lock_page - Lock the DAX entry corresponding to a page > * @page: The page whose entry we want to lock > * > * Context: Process context. > @@ -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; I kinda wonder if these open-coded magic values ~0UL (no entry) and 0 (cannot lock) should be #defines that force-cast the magic value to dax_entry_t... ...but then I'm not really an expert in the design behind fs/dax.c -- this part looks reasonable enough to me, but I think Dan or Matthew ought to look this over. --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 d273d59723cd..65411bee4312 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -156,6 +156,10 @@ 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 > #define generic_fsdax_supported NULL > > @@ -201,6 +205,17 @@ 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 > > #if IS_ENABLED(CONFIG_DAX) > -- > 2.33.0 > > >
diff --git a/fs/dax.c b/fs/dax.c index 798c43f09eee..509b65e60478 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -390,7 +390,7 @@ static struct page *dax_busy_page(void *entry) } /* - * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page + * dax_lock_page - Lock the DAX entry corresponding to a page * @page: The page whose entry we want to lock * * Context: Process context. @@ -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 d273d59723cd..65411bee4312 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -156,6 +156,10 @@ 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 #define generic_fsdax_supported NULL @@ -201,6 +205,17 @@ 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 #if IS_ENABLED(CONFIG_DAX)
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 BTW, output the page corresponding to the specific dax entry for caller use. Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> --- fs/dax.c | 65 ++++++++++++++++++++++++++++++++++++++++++++- include/linux/dax.h | 15 +++++++++++ 2 files changed, 79 insertions(+), 1 deletion(-)