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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 49/67] fscache: Add support for writing to the cache From: David Howells To: linux-cachefs@redhat.com Cc: dhowells@redhat.com, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Jeff Layton , Matthew Wilcox , Alexander Viro , Omar Sandoval , Linus Torvalds , linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 18 Oct 2021 16:02:27 +0100 Message-ID: <163456934704.2614702.13459517221637847782.stgit@warthog.procyon.org.uk> In-Reply-To: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk> References: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Add a pair of helpers for use by a netfs to write data to the cache. Signed-off-by: David Howells --- fs/fscache/io.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fscache.h | 58 +++++++++++++++++++++++++++ 2 files changed, 158 insertions(+) diff --git a/fs/fscache/io.c b/fs/fscache/io.c index 8b1a865a0847..3910cba65545 100644 --- a/fs/fscache/io.c +++ b/fs/fscache/io.c @@ -11,6 +11,7 @@ #include #include #include +#include #include "internal.h" /** @@ -278,3 +279,102 @@ void __fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size) } } EXPORT_SYMBOL(__fscache_resize_cookie); + +struct fscache_write_request { + struct netfs_cache_resources cache_resources; + struct address_space *mapping; + loff_t start; + size_t len; + netfs_io_terminated_t term_func; + void *term_func_priv; +}; + +void __fscache_clear_page_bits(struct address_space *mapping, + loff_t start, size_t len) +{ + pgoff_t first = start / PAGE_SIZE; + pgoff_t last = (start + len - 1) / PAGE_SIZE; + struct page *page; + + if (len) { + XA_STATE(xas, &mapping->i_pages, first); + + rcu_read_lock(); + xas_for_each(&xas, page, last) { + end_page_fscache(page); + } + rcu_read_unlock(); + } +} +EXPORT_SYMBOL(__fscache_clear_page_bits); + +/* + * Deal with the completion of writing the data to the cache. + */ +static void fscache_wreq_done(void *priv, ssize_t transferred_or_error, + bool was_async) +{ + struct fscache_write_request *wreq = priv; + + fscache_clear_page_bits(wreq->mapping, wreq->start, wreq->len); + + if (wreq->term_func) + wreq->term_func(wreq->term_func_priv, transferred_or_error, + was_async); + fscache_end_operation(&wreq->cache_resources); + kfree(wreq); +} + +void __fscache_write_to_cache(struct fscache_cookie *cookie, + struct address_space *mapping, + loff_t start, size_t len, loff_t i_size, + netfs_io_terminated_t term_func, + void *term_func_priv) +{ + struct fscache_write_request *wreq; + struct netfs_cache_resources *cres; + struct iov_iter iter; + int ret = -ENOBUFS; + + if (!fscache_cookie_valid(cookie) || len == 0) + goto abandon; + + _enter("%llx,%zx", start, len); + + wreq = kzalloc(sizeof(struct fscache_write_request), GFP_NOFS); + if (!wreq) + goto abandon; + wreq->mapping = mapping; + wreq->start = start; + wreq->len = len; + wreq->term_func = term_func; + wreq->term_func_priv = term_func_priv; + + cres = &wreq->cache_resources; + if (fscache_begin_operation(cres, cookie, FSCACHE_WANT_WRITE, + fscache_access_io_write) < 0) + goto abandon_free; + + ret = cres->ops->prepare_write(cres, &start, &len, i_size, false); + if (ret < 0) + goto abandon_end; + + /* TODO: Consider clearing page bits now for space the write isn't + * covering. This is more complicated than it appears when THPs are + * taken into account. + */ + + iov_iter_xarray(&iter, WRITE, &mapping->i_pages, start, len); + fscache_write(cres, start, &iter, fscache_wreq_done, wreq); + return; + +abandon_end: + return fscache_wreq_done(wreq, ret, false); +abandon_free: + kfree(wreq); +abandon: + fscache_clear_page_bits(mapping, start, len); + if (term_func) + term_func(term_func_priv, ret, false); +} +EXPORT_SYMBOL(__fscache_write_to_cache); diff --git a/include/linux/fscache.h b/include/linux/fscache.h index 8ab691e52cc5..fe4d588641da 100644 --- a/include/linux/fscache.h +++ b/include/linux/fscache.h @@ -176,6 +176,10 @@ extern int __fscache_fallback_read_page(struct fscache_cookie *, struct page *); extern int __fscache_fallback_write_page(struct fscache_cookie *, struct page *); #endif +extern void __fscache_write_to_cache(struct fscache_cookie *, struct address_space *, + loff_t, size_t, loff_t, netfs_io_terminated_t, void *); +extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t); + /** * fscache_acquire_volume - Register a volume as desiring caching services * @volume_key: An identification string for the volume @@ -543,6 +547,60 @@ int fscache_write(struct netfs_cache_resources *cres, return ops->write(cres, start_pos, iter, term_func, term_func_priv); } +/** + * fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages + * @mapping: The netfs inode to use as the source + * @start: The start position in @mapping + * @len: The amount of data to unlock + * + * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's + * waiting. + */ +static inline void fscache_clear_page_bits(struct address_space *mapping, + loff_t start, size_t len) +{ + if (fscache_available()) + __fscache_clear_page_bits(mapping, start, len); +} + +/** + * fscache_write_to_cache - Save a write to the cache and clear PG_fscache + * @cookie: The cookie representing the cache object + * @mapping: The netfs inode to use as the source + * @start: The start position in @mapping + * @len: The amount of data to write back + * @i_size: The new size of the inode + * @term_func: The function to call upon completion + * @term_func_priv: The private data for @term_func + * + * Helper function for a netfs to write dirty data from an inode into the cache + * object that's backing it. + * + * @start and @len describe the range of the data. This does not need to be + * page-aligned, but to satisfy DIO requirements, the cache may expand it up to + * the page boundaries on either end. All the pages covering the range must be + * marked with PG_fscache. + * + * If given, @term_func will be called upon completion and supplied with + * @term_func_priv. Note that the PG_fscache flags will have been cleared by + * this point, so the netfs must retain its own pin on the mapping. + */ +static inline void fscache_write_to_cache(struct fscache_cookie *cookie, + struct address_space *mapping, + loff_t start, size_t len, loff_t i_size, + netfs_io_terminated_t term_func, + void *term_func_priv) +{ + if (fscache_available()) { + __fscache_write_to_cache(cookie, mapping, start, len, i_size, + term_func, term_func_priv); + } else { + fscache_clear_page_bits(mapping, start, len); + if (term_func) + term_func(term_func_priv, -ENOBUFS, false); + } + +} #endif /* FSCACHE_USE_NEW_IO_API */ #if __fscache_available