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From: David Howells <dhowells@redhat.com>
To: linux-cachefs@redhat.com
Cc: dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Jeff Layton <jlayton@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Omar Sandoval <osandov@osandov.com>,
	JeffleXu <jefflexu@linux.alibaba.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	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
Subject: [PATCH v2 26/67] fscache: Implement higher-level write I/O interface
Date: Thu, 09 Dec 2021 16:59:23 +0000	[thread overview]
Message-ID: <163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <163906878733.143852.5604115678965006622.stgit@warthog.procyon.org.uk>

Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:

	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,
				    bool caching);

If caching is false, this function does nothing except call (*term_func)()
if given.  It assumes that, in such a case, PG_fscache will not have been
set on the pages.

Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling.  start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.

term_func and term_func_priv work as for fscache_write().  The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.

There is an additonal helper function to clear the PG_fscache bits from a
range of pages:

	void fscache_clear_page_bits(struct fscache_cookie *cookie,
				     struct address_space *mapping,
				     loff_t start, size_t len,
				     bool caching);

If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len.  If caching is false, it
does nothing.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
---

 fs/fscache/io.c         |  104 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fscache.h |   63 ++++++++++++++++++++++++++++
 2 files changed, 167 insertions(+)

diff --git a/fs/fscache/io.c b/fs/fscache/io.c
index 460a43473019..74cde7acf434 100644
--- a/fs/fscache/io.c
+++ b/fs/fscache/io.c
@@ -149,3 +149,107 @@ int __fscache_begin_read_operation(struct netfs_cache_resources *cres,
 				       fscache_access_io_read);
 }
 EXPORT_SYMBOL(__fscache_begin_read_operation);
+
+struct fscache_write_request {
+	struct netfs_cache_resources cache_resources;
+	struct address_space	*mapping;
+	loff_t			start;
+	size_t			len;
+	bool			set_bits;
+	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(fscache_cres_cookie(&wreq->cache_resources),
+				wreq->mapping, wreq->start, wreq->len,
+				wreq->set_bits);
+
+	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,
+			      bool cond)
+{
+	struct fscache_write_request *wreq;
+	struct netfs_cache_resources *cres;
+	struct iov_iter iter;
+	int ret = -ENOBUFS;
+
+	if (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->set_bits		= cond;
+	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(cookie, mapping, start, len, cond);
+	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 55ea296fe4db..1a018964d418 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -164,6 +164,11 @@ extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
 extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);
 extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
 
+extern void __fscache_write_to_cache(struct fscache_cookie *, struct address_space *,
+				     loff_t, size_t, loff_t, netfs_io_terminated_t, void *,
+				     bool);
+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
@@ -499,4 +504,62 @@ 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
+ * @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 unlock
+ * @caching: If PG_fscache has been set
+ *
+ * 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 fscache_cookie *cookie,
+					   struct address_space *mapping,
+					   loff_t start, size_t len,
+					   bool caching)
+{
+	if (caching)
+		__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
+ * @caching: If PG_fscache has been set
+ *
+ * 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,
+					  bool caching)
+{
+	if (caching)
+		__fscache_write_to_cache(cookie, mapping, start, len, i_size,
+					 term_func, term_func_priv, caching);
+	else if (term_func)
+		term_func(term_func_priv, -ENOBUFS, false);
+
+}
+
 #endif /* _LINUX_FSCACHE_H */



  parent reply	other threads:[~2021-12-09 16:59 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-09 16:53 [PATCH v2 00/67] fscache, cachefiles: Rewrite David Howells
2021-12-09 16:53 ` [PATCH v2 01/67] fscache, cachefiles: Disable configuration David Howells
2021-12-09 16:53 ` [PATCH v2 02/67] cachefiles: Delete the cachefiles driver pending rewrite David Howells
2021-12-09 16:54 ` [PATCH v2 03/67] fscache: Remove the contents of the fscache driver, " David Howells
2021-12-09 16:54 ` [PATCH v2 04/67] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells
2021-12-09 16:54 ` [PATCH v2 05/67] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells
2021-12-09 16:54 ` [PATCH v2 06/67] fscache: Introduce new driver David Howells
2021-12-09 16:54 ` [PATCH v2 07/67] fscache: Implement a hash function David Howells
2021-12-09 17:12   ` Linus Torvalds
2021-12-09 21:57   ` David Howells
2021-12-09 22:07     ` Linus Torvalds
2021-12-10 14:35     ` David Howells
2021-12-10 14:41     ` David Howells
2021-12-10 17:33       ` Linus Torvalds
2021-12-09 16:54 ` [PATCH v2 08/67] fscache: Implement cache registration David Howells
2021-12-14 18:36   ` Jeff Layton
2021-12-09 16:55 ` [PATCH v2 09/67] fscache: Implement volume registration David Howells
2021-12-09 17:32   ` Linus Torvalds
2021-12-14 18:52   ` Jeff Layton
2021-12-14 19:57   ` David Howells
2021-12-09 16:55 ` [PATCH v2 10/67] fscache: Implement cookie registration David Howells
2021-12-09 17:21   ` Linus Torvalds
2021-12-09 16:55 ` [PATCH v2 11/67] fscache: Implement cache-level access helpers David Howells
2021-12-09 16:55 ` [PATCH v2 12/67] fscache: Implement volume-level " David Howells
2021-12-09 16:55 ` [PATCH v2 13/67] fscache: Implement cookie-level " David Howells
2021-12-09 16:56 ` [PATCH v2 14/67] fscache: Implement functions add/remove a cache David Howells
2021-12-09 16:56 ` [PATCH v2 15/67] fscache: Provide and use cache methods to lookup/create/free a volume David Howells
2021-12-09 16:56 ` [PATCH v2 16/67] fscache: Add a function for a cache backend to note an I/O error David Howells
2021-12-09 16:57 ` [PATCH v2 17/67] fscache: Implement simple cookie state machine David Howells
2021-12-09 16:57 ` [PATCH v2 18/67] fscache: Implement cookie user counting and resource pinning David Howells
2021-12-09 16:58 ` [PATCH v2 19/67] fscache: Implement cookie invalidation David Howells
2021-12-09 16:58 ` [PATCH v2 20/67] fscache: Provide a means to begin an operation David Howells
2021-12-09 16:58 ` [PATCH v2 21/67] fscache: Count data storage objects in a cache David Howells
2021-12-09 16:58 ` [PATCH v2 22/67] fscache: Provide read/write stat counters for the cache David Howells
2021-12-09 16:58 ` [PATCH v2 23/67] fscache: Provide a function to let the netfs update its coherency data David Howells
2021-12-09 16:59 ` [PATCH v2 24/67] netfs: Pass more information on how to deal with a hole in the cache David Howells
2021-12-09 16:59 ` [PATCH v2 25/67] fscache: Implement raw I/O interface David Howells
2021-12-09 16:59 ` David Howells [this message]
2021-12-09 16:59 ` [PATCH v2 27/67] vfs, fscache: Implement pinning of cache usage for writeback David Howells
2021-12-09 17:00 ` [PATCH v2 28/67] fscache: Provide a function to note the release of a page David Howells
2021-12-09 17:00 ` [PATCH v2 29/67] fscache: Provide a function to resize a cookie David Howells
2021-12-09 17:00 ` [PATCH v2 30/67] cachefiles: Introduce rewritten driver David Howells
2021-12-09 17:00 ` [PATCH v2 31/67] cachefiles: Define structs David Howells
2021-12-09 17:00 ` [PATCH v2 32/67] cachefiles: Add some error injection support David Howells
2021-12-09 17:01 ` [PATCH v2 33/67] cachefiles: Add a couple of tracepoints for logging errors David Howells
2021-12-09 17:01 ` [PATCH v2 34/67] cachefiles: Add cache error reporting macro David Howells
2021-12-09 17:01 ` [PATCH v2 35/67] cachefiles: Add security derivation David Howells
2021-12-09 17:01 ` [PATCH v2 36/67] cachefiles: Register a miscdev and parse commands over it David Howells
2021-12-09 17:01 ` [PATCH v2 37/67] cachefiles: Provide a function to check how much space there is David Howells
2021-12-09 17:01 ` [PATCH v2 38/67] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells
2021-12-09 17:02 ` [PATCH v2 39/67] cachefiles: Implement a function to get/create a directory in the cache David Howells
2021-12-09 17:02 ` [PATCH v2 40/67] cachefiles: Implement cache registration and withdrawal David Howells
2021-12-09 17:02 ` [PATCH v2 41/67] cachefiles: Implement volume support David Howells
2021-12-09 17:03 ` [PATCH v2 42/67] cachefiles: Add tracepoints for calls to the VFS David Howells
2021-12-09 17:03 ` [PATCH v2 43/67] cachefiles: Implement object lifecycle funcs David Howells
2021-12-09 17:03 ` [PATCH v2 44/67] cachefiles: Implement key to filename encoding David Howells
2021-12-09 17:03 ` [PATCH v2 45/67] cachefiles: Implement metadata/coherency data storage in xattrs David Howells
2021-12-09 17:03 ` [PATCH v2 46/67] cachefiles: Mark a backing file in use with an inode flag David Howells
2021-12-09 17:04 ` [PATCH v2 47/67] cachefiles: Implement culling daemon commands David Howells
2021-12-09 17:04 ` [PATCH v2 48/67] cachefiles: Implement backing file wrangling David Howells
2021-12-09 17:05 ` [PATCH v2 49/67] cachefiles: Implement begin and end I/O operation David Howells
2021-12-09 17:05 ` [PATCH v2 50/67] cachefiles: Implement cookie resize for truncate David Howells
2021-12-09 17:05 ` [PATCH v2 51/67] cachefiles: Implement the I/O routines David Howells
2021-12-09 17:06 ` [PATCH v2 52/67] cachefiles: Allow cachefiles to actually function David Howells
2021-12-09 17:06 ` [PATCH v2 53/67] fscache, cachefiles: Display stats of no-space events David Howells
2021-12-09 17:06 ` [PATCH v2 54/67] fscache, cachefiles: Display stat of culling events David Howells
2021-12-09 17:07 ` [PATCH v2 55/67] afs: Handle len being extending over page end in write_begin/write_end David Howells
2021-12-09 17:08 ` [PATCH v2 56/67] afs: Fix afs_write_end() to handle len > page size David Howells
2021-12-09 17:08 ` [PATCH v2 57/67] afs: Convert afs to use the new fscache API David Howells
2021-12-09 17:08 ` [PATCH v2 58/67] afs: Copy local writes to the cache when writing to the server David Howells
2021-12-09 17:08 ` [PATCH v2 59/67] afs: Skip truncation on the server of data we haven't written yet David Howells
2021-12-09 17:09 ` [PATCH v2 60/67] 9p: Use fscache indexing rewrite and reenable caching David Howells
2021-12-09 17:09 ` [PATCH v2 61/67] 9p: Copy local writes to the cache when writing to the server David Howells
2021-12-09 17:09 ` [PATCH v2 62/67] nfs: Convert to new fscache volume/cookie API David Howells
2021-12-11 13:22   ` David Wysochanski
2021-12-11 13:37   ` David Howells
2021-12-09 17:10 ` [PATCH v2 63/67] nfs: Implement cache I/O by accessing the cache directly David Howells
2021-12-09 17:10 ` [PATCH v2 64/67] cifs: Support fscache indexing rewrite (untested) David Howells
2021-12-09 17:10 ` [PATCH v2 65/67] ceph: conversion to new fscache API David Howells
2021-12-09 17:10 ` [PATCH v2 66/67] ceph: add fscache writeback support David Howells
2021-12-09 17:11 ` [PATCH v2 67/67] fscache: Rewrite documentation David Howells
2021-12-10 18:38 ` [PATCH v2 00/67] fscache, cachefiles: Rewrite David Wysochanski
2021-12-11 13:44   ` David Wysochanski
2021-12-13 15:41   ` [PATCH] fscache: Need to go round again after processing LRU_DISCARDING state David Howells
2021-12-13 21:05     ` David Wysochanski
2021-12-13 16:22   ` David Howells
2021-12-13 20:03   ` David Howells
2021-12-13 22:39   ` David Howells

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