Merge remote-tracking branch 'dhowells/netfs-lib'

Pick up David Howells' netfs helper library and the new fscache API.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Documentation/filesystems/index.rst

@@ -53,6 +53,7 @@ filesystem implementations.
    journalling
    fscrypt
    fsverity
+   netfs_library
 
 Filesystems
 ===========

fs/Kconfig

@@ -125,6 +125,7 @@ source "fs/overlayfs/Kconfig"
 
 menu "Caches"
 
+source "fs/netfs/Kconfig"
 source "fs/fscache/Kconfig"
 source "fs/cachefiles/Kconfig"
 

fs/Makefile

@@ -67,6 +67,7 @@ obj-y				+= devpts/
 obj-$(CONFIG_DLM)		+= dlm/
  
 # Do not add any filesystems before this line
+obj-$(CONFIG_NETFS_SUPPORT)	+= netfs/
 obj-$(CONFIG_FSCACHE)		+= fscache/
 obj-$(CONFIG_REISERFS_FS)	+= reiserfs/
 obj-$(CONFIG_EXT4_FS)		+= ext4/

fs/cachefiles/Makefile

@@ -7,6 +7,7 @@ cachefiles-y := \
 	bind.o \
 	daemon.o \
 	interface.o \
+	io.o \
 	key.o \
 	main.o \
 	namei.o \

fs/cachefiles/interface.c

@@ -319,7 +319,7 @@ static void cachefiles_drop_object(struct fscache_object *_object)
 /*
  * dispose of a reference to an object
  */
-static void cachefiles_put_object(struct fscache_object *_object,
+void cachefiles_put_object(struct fscache_object *_object,
 			   enum fscache_obj_ref_trace why)
 {
 	struct cachefiles_object *object;
@@ -568,4 +568,5 @@ const struct fscache_cache_ops cachefiles_cache_ops = {
 	.uncache_page		= cachefiles_uncache_page,
 	.dissociate_pages	= cachefiles_dissociate_pages,
 	.check_consistency	= cachefiles_check_consistency,
+	.begin_read_operation	= cachefiles_begin_read_operation,
 };

fs/cachefiles/internal.h

@@ -150,6 +150,9 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache,
  */
 extern const struct fscache_cache_ops cachefiles_cache_ops;
 
+void cachefiles_put_object(struct fscache_object *_object,
+			   enum fscache_obj_ref_trace why);
+
 /*
  * key.c
  */
@@ -217,6 +220,12 @@ extern int cachefiles_allocate_pages(struct fscache_retrieval *,
 extern int cachefiles_write_page(struct fscache_storage *, struct page *);
 extern void cachefiles_uncache_page(struct fscache_object *, struct page *);
 
+/*
+ * rdwr2.c
+ */
+extern int cachefiles_begin_read_operation(struct netfs_read_request *,
+					   struct fscache_retrieval *);
+
 /*
  * security.c
  */

fs/ext4/verity.c

@@ -370,7 +370,7 @@ static struct page *ext4_read_merkle_tree_page(struct inode *inode,
 					       pgoff_t index,
 					       unsigned long num_ra_pages)
 {
-	DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, index);
+	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
 	struct page *page;
 
 	index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;

fs/f2fs/file.c

@@ -4051,7 +4051,7 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
 
 static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 {
-	DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, page_idx);
+	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, page_idx);
 	struct address_space *mapping = inode->i_mapping;
 	struct page *page;
 	pgoff_t redirty_idx = page_idx;

fs/f2fs/verity.c

@@ -228,7 +228,7 @@ static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
 					       pgoff_t index,
 					       unsigned long num_ra_pages)
 {
-	DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, index);
+	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
 	struct page *page;
 
 	index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;

fs/fscache/Kconfig

@@ -2,6 +2,7 @@
 
 config FSCACHE
 	tristate "General filesystem local caching manager"
+	select NETFS_SUPPORT
 	help
 	  This option enables a generic filesystem caching manager that can be
 	  used by various network and other filesystems to cache data locally.

fs/fscache/Makefile

@@ -7,6 +7,7 @@ fscache-y := \
 	cache.o \
 	cookie.o \
 	fsdef.o \
+	io.o \
 	main.o \
 	netfs.o \
 	object.o \

fs/fscache/internal.h

@@ -142,6 +142,10 @@ extern int fscache_wait_for_operation_activation(struct fscache_object *,
 						 atomic_t *,
 						 atomic_t *);
 extern void fscache_invalidate_writes(struct fscache_cookie *);
+struct fscache_retrieval *fscache_alloc_retrieval(struct fscache_cookie *cookie,
+						  struct address_space *mapping,
+						  fscache_rw_complete_t end_io_func,
+						  void *context);
 
 /*
  * proc.c

fs/fscache/io.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Cache data I/O routines
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define FSCACHE_DEBUG_LEVEL PAGE
+#include <linux/module.h>
+#define FSCACHE_USE_NEW_IO_API
+#include <linux/fscache-cache.h>
+#include <linux/slab.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+/*
+ * Start a cache read operation.
+ * - we return:
+ *   -ENOMEM	- out of memory, some pages may be being read
+ *   -ERESTARTSYS - interrupted, some pages may be being read
+ *   -ENOBUFS	- no backing object or space available in which to cache any
+ *                pages not being read
+ *   -ENODATA	- no data available in the backing object for some or all of
+ *                the pages
+ *   0		- dispatched a read on all pages
+ */
+int __fscache_begin_read_operation(struct netfs_read_request *rreq,
+				   struct fscache_cookie *cookie)
+{
+	struct fscache_retrieval *op;
+	struct fscache_object *object;
+	bool wake_cookie = false;
+	int ret;
+
+	_enter("rr=%08x", rreq->debug_id);
+
+	fscache_stat(&fscache_n_retrievals);
+
+	if (hlist_empty(&cookie->backing_objects))
+		goto nobufs;
+
+	if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
+		_leave(" = -ENOBUFS [invalidating]");
+		return -ENOBUFS;
+	}
+
+	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
+
+	if (fscache_wait_for_deferred_lookup(cookie) < 0)
+		return -ERESTARTSYS;
+
+	op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
+	if (!op)
+		return -ENOMEM;
+	trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
+
+	spin_lock(&cookie->lock);
+
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
+		goto nobufs_unlock;
+	object = hlist_entry(cookie->backing_objects.first,
+			     struct fscache_object, cookie_link);
+
+	__fscache_use_cookie(cookie);
+	atomic_inc(&object->n_reads);
+	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
+
+	if (fscache_submit_op(object, &op->op) < 0)
+		goto nobufs_unlock_dec;
+	spin_unlock(&cookie->lock);
+
+	fscache_stat(&fscache_n_retrieval_ops);
+
+	/* we wait for the operation to become active, and then process it
+	 * *here*, in this thread, and not in the thread pool */
+	ret = fscache_wait_for_operation_activation(
+		object, &op->op,
+		__fscache_stat(&fscache_n_retrieval_op_waits),
+		__fscache_stat(&fscache_n_retrievals_object_dead));
+	if (ret < 0)
+		goto error;
+
+	/* ask the cache to honour the operation */
+	ret = object->cache->ops->begin_read_operation(rreq, op);
+
+error:
+	if (ret == -ENOMEM)
+		fscache_stat(&fscache_n_retrievals_nomem);
+	else if (ret == -ERESTARTSYS)
+		fscache_stat(&fscache_n_retrievals_intr);
+	else if (ret == -ENODATA)
+		fscache_stat(&fscache_n_retrievals_nodata);
+	else if (ret < 0)
+		fscache_stat(&fscache_n_retrievals_nobufs);
+	else
+		fscache_stat(&fscache_n_retrievals_ok);
+
+	fscache_put_retrieval(op);
+	_leave(" = %d", ret);
+	return ret;
+
+nobufs_unlock_dec:
+	atomic_dec(&object->n_reads);
+	wake_cookie = __fscache_unuse_cookie(cookie);
+nobufs_unlock:
+	spin_unlock(&cookie->lock);
+	fscache_put_retrieval(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
+nobufs:
+	fscache_stat(&fscache_n_retrievals_nobufs);
+	_leave(" = -ENOBUFS");
+	return -ENOBUFS;
+}
+EXPORT_SYMBOL(__fscache_begin_read_operation);

fs/fscache/page.c

@@ -299,7 +299,7 @@ static void fscache_release_retrieval_op(struct fscache_operation *_op)
 /*
  * allocate a retrieval op
  */
-static struct fscache_retrieval *fscache_alloc_retrieval(
+struct fscache_retrieval *fscache_alloc_retrieval(
 	struct fscache_cookie *cookie,
 	struct address_space *mapping,
 	fscache_rw_complete_t end_io_func,

fs/fscache/stats.c

@@ -278,5 +278,6 @@ int fscache_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&fscache_n_cache_stale_objects),
 		   atomic_read(&fscache_n_cache_retired_objects),
 		   atomic_read(&fscache_n_cache_culled_objects));
+	netfs_stats_show(m);
 	return 0;
 }

fs/netfs/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+
+config NETFS_SUPPORT
+	tristate "Support for network filesystem high-level I/O"
+	help
+	  This option enables support for network filesystems, including
+	  helpers for high-level buffered I/O, abstracting out read
+	  segmentation, local caching and transparent huge page support.
+
+config NETFS_STATS
+	bool "Gather statistical information on local caching"
+	depends on NETFS_SUPPORT && PROC_FS
+	help
+	  This option causes statistical information to be gathered on local
+	  caching and exported through file:
+
+		/proc/fs/fscache/stats
+
+	  The gathering of statistics adds a certain amount of overhead to
+	  execution as there are a quite a few stats gathered, and on a
+	  multi-CPU system these may be on cachelines that keep bouncing
+	  between CPUs.  On the other hand, the stats are very useful for
+	  debugging purposes.  Saying 'Y' here is recommended.

fs/netfs/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+netfs-y := read_helper.o stats.o
+
+obj-$(CONFIG_NETFS_SUPPORT) := netfs.o

fs/netfs/internal.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Internal definitions for network filesystem support
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) "netfs: " fmt
+
+/*
+ * read_helper.c
+ */
+extern unsigned int netfs_debug;
+
+/*
+ * stats.c
+ */
+#ifdef CONFIG_NETFS_STATS
+extern atomic_t netfs_n_rh_readahead;
+extern atomic_t netfs_n_rh_readpage;
+extern atomic_t netfs_n_rh_rreq;
+extern atomic_t netfs_n_rh_sreq;
+extern atomic_t netfs_n_rh_download;
+extern atomic_t netfs_n_rh_download_done;
+extern atomic_t netfs_n_rh_download_failed;
+extern atomic_t netfs_n_rh_download_instead;
+extern atomic_t netfs_n_rh_read;
+extern atomic_t netfs_n_rh_read_done;
+extern atomic_t netfs_n_rh_read_failed;
+extern atomic_t netfs_n_rh_zero;
+extern atomic_t netfs_n_rh_short_read;
+extern atomic_t netfs_n_rh_write;
+extern atomic_t netfs_n_rh_write_begin;
+extern atomic_t netfs_n_rh_write_done;
+extern atomic_t netfs_n_rh_write_failed;
+extern atomic_t netfs_n_rh_write_zskip;
+
+
+static inline void netfs_stat(atomic_t *stat)
+{
+	atomic_inc(stat);
+}
+
+static inline void netfs_stat_d(atomic_t *stat)
+{
+	atomic_dec(stat);
+}
+
+#else
+#define netfs_stat(x) do {} while(0)
+#define netfs_stat_d(x) do {} while(0)
+#endif
+
+/*****************************************************************************/
+/*
+ * debug tracing
+ */
+#define dbgprintk(FMT, ...) \
+	printk("[%-6.6s] "FMT"\n", current->comm, ##__VA_ARGS__)
+
+#define kenter(FMT, ...) dbgprintk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__)
+
+#ifdef __KDEBUG
+#define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__)
+#define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__)
+#define _debug(FMT, ...) kdebug(FMT, ##__VA_ARGS__)
+
+#elif defined(CONFIG_NETFS_DEBUG)
+#define _enter(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kenter(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#define _leave(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kleave(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#define _debug(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kdebug(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#else
+#define _enter(FMT, ...) no_printk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define _leave(FMT, ...) no_printk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define _debug(FMT, ...) no_printk(FMT, ##__VA_ARGS__)
+#endif

fs/netfs/stats.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Netfs support statistics
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/seq_file.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+atomic_t netfs_n_rh_readahead;
+atomic_t netfs_n_rh_readpage;
+atomic_t netfs_n_rh_rreq;
+atomic_t netfs_n_rh_sreq;
+atomic_t netfs_n_rh_download;
+atomic_t netfs_n_rh_download_done;
+atomic_t netfs_n_rh_download_failed;
+atomic_t netfs_n_rh_download_instead;
+atomic_t netfs_n_rh_read;
+atomic_t netfs_n_rh_read_done;
+atomic_t netfs_n_rh_read_failed;
+atomic_t netfs_n_rh_zero;
+atomic_t netfs_n_rh_short_read;
+atomic_t netfs_n_rh_write;
+atomic_t netfs_n_rh_write_begin;
+atomic_t netfs_n_rh_write_done;
+atomic_t netfs_n_rh_write_failed;
+atomic_t netfs_n_rh_write_zskip;
+
+void netfs_stats_show(struct seq_file *m)
+{
+	seq_printf(m, "RdHelp : RA=%u RP=%u WB=%u WBZ=%u rr=%u sr=%u\n",
+		   atomic_read(&netfs_n_rh_readahead),
+		   atomic_read(&netfs_n_rh_readpage),
+		   atomic_read(&netfs_n_rh_write_begin),
+		   atomic_read(&netfs_n_rh_write_zskip),
+		   atomic_read(&netfs_n_rh_rreq),
+		   atomic_read(&netfs_n_rh_sreq));
+	seq_printf(m, "RdHelp : ZR=%u sh=%u sk=%u\n",
+		   atomic_read(&netfs_n_rh_zero),
+		   atomic_read(&netfs_n_rh_short_read),
+		   atomic_read(&netfs_n_rh_write_zskip));
+	seq_printf(m, "RdHelp : DL=%u ds=%u df=%u di=%u\n",
+		   atomic_read(&netfs_n_rh_download),
+		   atomic_read(&netfs_n_rh_download_done),
+		   atomic_read(&netfs_n_rh_download_failed),
+		   atomic_read(&netfs_n_rh_download_instead));
+	seq_printf(m, "RdHelp : RD=%u rs=%u rf=%u\n",
+		   atomic_read(&netfs_n_rh_read),
+		   atomic_read(&netfs_n_rh_read_done),
+		   atomic_read(&netfs_n_rh_read_failed));
+	seq_printf(m, "RdHelp : WR=%u ws=%u wf=%u\n",
+		   atomic_read(&netfs_n_rh_write),
+		   atomic_read(&netfs_n_rh_write_done),
+		   atomic_read(&netfs_n_rh_write_failed));
+}
+EXPORT_SYMBOL(netfs_stats_show);

include/linux/fs.h

@@ -891,18 +891,22 @@ struct fown_struct {
 	int signum;		/* posix.1b rt signal to be delivered on IO */
 };
 
-/*
- * Track a single file's readahead state
+/**
+ * struct file_ra_state - Track a file's readahead state.
+ * @start: Where the most recent readahead started.
+ * @size: Number of pages read in the most recent readahead.
+ * @async_size: Start next readahead when this many pages are left.
+ * @ra_pages: Maximum size of a readahead request.
+ * @mmap_miss: How many mmap accesses missed in the page cache.
+ * @prev_pos: The last byte in the most recent read request.
  */
 struct file_ra_state {
-	pgoff_t start;			/* where readahead started */
-	unsigned int size;		/* # of readahead pages */
-	unsigned int async_size;	/* do asynchronous readahead when
-					   there are only # of pages ahead */
-
-	unsigned int ra_pages;		/* Maximum readahead window */
-	unsigned int mmap_miss;		/* Cache miss stat for mmap accesses */
-	loff_t prev_pos;		/* Cache last read() position */
+	pgoff_t start;
+	unsigned int size;
+	unsigned int async_size;
+	unsigned int ra_pages;
+	unsigned int mmap_miss;
+	loff_t prev_pos;
 };
 
 /*

include/linux/fscache-cache.h

@@ -304,6 +304,10 @@ struct fscache_cache_ops {
 
 	/* dissociate a cache from all the pages it was backing */
 	void (*dissociate_pages)(struct fscache_cache *cache);
+
+	/* Begin a read operation for the netfs lib */
+	int (*begin_read_operation)(struct netfs_read_request *rreq,
+				    struct fscache_retrieval *op);
 };
 
 extern struct fscache_cookie fscache_fsdef_index;

include/linux/fscache.h

@@ -19,6 +19,7 @@
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 #include <linux/list_bl.h>
+#include <linux/netfs.h>
 
 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
 #define fscache_available() (1)
@@ -29,16 +30,6 @@
 #endif
 
 
-/*
- * overload PG_private_2 to give us PG_fscache - this is used to indicate that
- * a page is currently backed by a local disk cache
- */
-#define PageFsCache(page)		PagePrivate2((page))
-#define SetPageFsCache(page)		SetPagePrivate2((page))
-#define ClearPageFsCache(page)		ClearPagePrivate2((page))
-#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
-#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
-
 /* pattern used to fill dead space in an index entry */
 #define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
 
@@ -46,6 +37,7 @@ struct pagevec;
 struct fscache_cache_tag;
 struct fscache_cookie;
 struct fscache_netfs;
+struct netfs_read_request;
 
 typedef void (*fscache_rw_complete_t)(struct page *page,
 				      void *context,
@@ -200,6 +192,10 @@ extern void __fscache_update_cookie(struct fscache_cookie *, const void *);
 extern int __fscache_attr_changed(struct fscache_cookie *);
 extern void __fscache_invalidate(struct fscache_cookie *);
 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
+
+#ifdef FSCACHE_USE_NEW_IO_API
+extern int __fscache_begin_read_operation(struct netfs_read_request *, struct fscache_cookie *);
+#else
 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
 					struct page *,
 					fscache_rw_complete_t,
@@ -223,6 +219,8 @@ extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
 					      struct inode *);
 extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 				       struct list_head *pages);
+#endif /* FSCACHE_USE_NEW_IO_API */
+
 extern void __fscache_disable_cookie(struct fscache_cookie *, const void *, bool);
 extern void __fscache_enable_cookie(struct fscache_cookie *, const void *, loff_t,
 				    bool (*)(void *), void *);
@@ -507,6 +505,36 @@ int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 	return -ENOBUFS;
 }
 
+#ifdef FSCACHE_USE_NEW_IO_API
+
+/**
+ * fscache_begin_read_operation - Begin a read operation for the netfs lib
+ * @rreq: The read request being undertaken
+ * @cookie: The cookie representing the cache object
+ *
+ * Begin a read operation on behalf of the netfs helper library.  @rreq
+ * indicates the read request to which the operation state should be attached;
+ * @cookie indicates the cache object that will be accessed.
+ *
+ * This is intended to be called from the ->begin_cache_operation() netfs lib
+ * operation as implemented by the network filesystem.
+ *
+ * Returns:
+ * * 0		- Success
+ * * -ENOBUFS	- No caching available
+ * * Other error code from the cache, such as -ENOMEM.
+ */
+static inline
+int fscache_begin_read_operation(struct netfs_read_request *rreq,
+				 struct fscache_cookie *cookie)
+{
+	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
+		return __fscache_begin_read_operation(rreq, cookie);
+	return -ENOBUFS;
+}
+
+#else /* FSCACHE_USE_NEW_IO_API */
+
 /**
  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
  * in which to store it
@@ -786,6 +814,8 @@ void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 		__fscache_uncache_all_inode_pages(cookie, inode);
 }
 
+#endif /* FSCACHE_USE_NEW_IO_API */
+
 /**
  * fscache_disable_cookie - Disable a cookie
  * @cookie: The cookie representing the cache object

include/linux/netfs.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Network filesystem support services.
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See:
+ *
+ *	Documentation/filesystems/netfs_library.rst
+ *
+ * for a description of the network filesystem interface declared here.
+ */
+
+#ifndef _LINUX_NETFS_H
+#define _LINUX_NETFS_H
+
+#include <linux/workqueue.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+
+/*
+ * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
+ * a page is currently backed by a local disk cache
+ */
+#define PageFsCache(page)		PagePrivate2((page))
+#define SetPageFsCache(page)		SetPagePrivate2((page))
+#define ClearPageFsCache(page)		ClearPagePrivate2((page))
+#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
+#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
+
+/**
+ * set_page_fscache - Set PG_fscache on a page and take a ref
+ * @page: The page.
+ *
+ * Set the PG_fscache (PG_private_2) flag on a page and take the reference
+ * needed for the VM to handle its lifetime correctly.  This sets the flag and
+ * takes the reference unconditionally, so care must be taken not to set the
+ * flag again if it's already set.
+ */
+static inline void set_page_fscache(struct page *page)
+{
+	set_page_private_2(page);
+}
+
+/**
+ * end_page_fscache - Clear PG_fscache and release any waiters
+ * @page: The page
+ *
+ * Clear the PG_fscache (PG_private_2) bit on a page and wake up any sleepers
+ * waiting for this.  The page ref held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+static inline void end_page_fscache(struct page *page)
+{
+	end_page_private_2(page);
+}
+
+/**
+ * wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_fscache (aka PG_private_2) to be cleared on a page.
+ */
+static inline void wait_on_page_fscache(struct page *page)
+{
+	wait_on_page_private_2(page);
+}
+
+/**
+ * wait_on_page_fscache_killable - Wait for PG_fscache to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_fscache (aka PG_private_2) to be cleared on a page or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+static inline int wait_on_page_fscache_killable(struct page *page)
+{
+	return wait_on_page_private_2_killable(page);
+}
+
+enum netfs_read_source {
+	NETFS_FILL_WITH_ZEROES,
+	NETFS_DOWNLOAD_FROM_SERVER,
+	NETFS_READ_FROM_CACHE,
+	NETFS_INVALID_READ,
+} __mode(byte);
+
+typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
+				      bool was_async);
+
+/*
+ * Resources required to do operations on a cache.
+ */
+struct netfs_cache_resources {
+	const struct netfs_cache_ops	*ops;
+	void				*cache_priv;
+	void				*cache_priv2;
+};
+
+/*
+ * Descriptor for a single component subrequest.
+ */
+struct netfs_read_subrequest {
+	struct netfs_read_request *rreq;	/* Supervising read request */
+	struct list_head	rreq_link;	/* Link in rreq->subrequests */
+	loff_t			start;		/* Where to start the I/O */
+	size_t			len;		/* Size of the I/O */
+	size_t			transferred;	/* Amount of data transferred */
+	refcount_t		usage;
+	short			error;		/* 0 or error that occurred */
+	unsigned short		debug_index;	/* Index in list (for debugging output) */
+	enum netfs_read_source	source;		/* Where to read from */
+	unsigned long		flags;
+#define NETFS_SREQ_WRITE_TO_CACHE	0	/* Set if should write to cache */
+#define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
+#define NETFS_SREQ_SHORT_READ		2	/* Set if there was a short read from the cache */
+#define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */
+#define NETFS_SREQ_NO_PROGRESS		4	/* Set if we didn't manage to read any data */
+};
+
+/*
+ * Descriptor for a read helper request.  This is used to make multiple I/O
+ * requests on a variety of sources and then stitch the result together.
+ */
+struct netfs_read_request {
+	struct work_struct	work;
+	struct inode		*inode;		/* The file being accessed */
+	struct address_space	*mapping;	/* The mapping being accessed */
+	struct netfs_cache_resources cache_resources;
+	struct list_head	subrequests;	/* Requests to fetch I/O from disk or net */
+	void			*netfs_priv;	/* Private data for the netfs */
+	unsigned int		debug_id;
+	unsigned int		cookie_debug_id;
+	atomic_t		nr_rd_ops;	/* Number of read ops in progress */
+	atomic_t		nr_wr_ops;	/* Number of write ops in progress */
+	size_t			submitted;	/* Amount submitted for I/O so far */
+	size_t			len;		/* Length of the request */
+	short			error;		/* 0 or error that occurred */
+	loff_t			i_size;		/* Size of the file */
+	loff_t			start;		/* Start position */
+	pgoff_t			no_unlock_page;	/* Don't unlock this page after read */
+	refcount_t		usage;
+	unsigned long		flags;
+#define NETFS_RREQ_INCOMPLETE_IO	0	/* Some ioreqs terminated short or with error */
+#define NETFS_RREQ_WRITE_TO_CACHE	1	/* Need to write to the cache */
+#define NETFS_RREQ_NO_UNLOCK_PAGE	2	/* Don't unlock no_unlock_page on completion */
+#define NETFS_RREQ_DONT_UNLOCK_PAGES	3	/* Don't unlock the pages on completion */
+#define NETFS_RREQ_FAILED		4	/* The request failed */
+#define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
+	const struct netfs_read_request_ops *netfs_ops;
+};
+
+/*
+ * Operations the network filesystem can/must provide to the helpers.
+ */
+struct netfs_read_request_ops {
+	bool (*is_cache_enabled)(struct inode *inode);
+	void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
+	int (*begin_cache_operation)(struct netfs_read_request *rreq);
+	void (*expand_readahead)(struct netfs_read_request *rreq);
+	bool (*clamp_length)(struct netfs_read_subrequest *subreq);
+	void (*issue_op)(struct netfs_read_subrequest *subreq);
+	bool (*is_still_valid)(struct netfs_read_request *rreq);
+	int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
+				 struct page *page, void **_fsdata);
+	void (*done)(struct netfs_read_request *rreq);
+	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
+};
+
+/*
+ * Table of operations for access to a cache.  This is obtained by
+ * rreq->ops->begin_cache_operation().
+ */
+struct netfs_cache_ops {
+	/* End an operation */
+	void (*end_operation)(struct netfs_cache_resources *cres);
+
+	/* Read data from the cache */
+	int (*read)(struct netfs_cache_resources *cres,
+		    loff_t start_pos,
+		    struct iov_iter *iter,
+		    bool seek_data,
+		    netfs_io_terminated_t term_func,
+		    void *term_func_priv);
+
+	/* Write data to the cache */
+	int (*write)(struct netfs_cache_resources *cres,
+		     loff_t start_pos,
+		     struct iov_iter *iter,
+		     netfs_io_terminated_t term_func,
+		     void *term_func_priv);
+
+	/* Expand readahead request */
+	void (*expand_readahead)(struct netfs_cache_resources *cres,
+				 loff_t *_start, size_t *_len, loff_t i_size);
+
+	/* Prepare a read operation, shortening it to a cached/uncached
+	 * boundary as appropriate.
+	 */
+	enum netfs_read_source (*prepare_read)(struct netfs_read_subrequest *subreq,
+					       loff_t i_size);
+
+	/* Prepare a write operation, working out what part of the write we can
+	 * actually do.
+	 */
+	int (*prepare_write)(struct netfs_cache_resources *cres,
+			     loff_t *_start, size_t *_len, loff_t i_size);
+};
+
+struct readahead_control;
+extern void netfs_readahead(struct readahead_control *,
+			    const struct netfs_read_request_ops *,
+			    void *);
+extern int netfs_readpage(struct file *,
+			  struct page *,
+			  const struct netfs_read_request_ops *,
+			  void *);
+extern int netfs_write_begin(struct file *, struct address_space *,
+			     loff_t, unsigned int, unsigned int, struct page **,
+			     void **,
+			     const struct netfs_read_request_ops *,
+			     void *);
+
+extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
+extern void netfs_stats_show(struct seq_file *);
+
+#endif /* _LINUX_NETFS_H */

include/linux/pagemap.h

@@ -688,6 +688,26 @@ void wait_for_stable_page(struct page *page);
 
 void page_endio(struct page *page, bool is_write, int err);
 
+/**
+ * set_page_private_2 - Set PG_private_2 on a page and take a ref
+ * @page: The page.
+ *
+ * Set the PG_private_2 flag on a page and take the reference needed for the VM
+ * to handle its lifetime correctly.  This sets the flag and takes the
+ * reference unconditionally, so care must be taken not to set the flag again
+ * if it's already set.
+ */
+static inline void set_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	get_page(page);
+	SetPagePrivate2(page);
+}
+
+void end_page_private_2(struct page *page);
+void wait_on_page_private_2(struct page *page);
+int wait_on_page_private_2_killable(struct page *page);
+
 /*
  * Add an arbitrary waiter to a page's wait queue
  */
@@ -792,20 +812,23 @@ static inline int add_to_page_cache(struct page *page,
  * @file: The file, used primarily by network filesystems for authentication.
  *	  May be NULL if invoked internally by the filesystem.
  * @mapping: Readahead this filesystem object.
+ * @ra: File readahead state.  May be NULL.
  */
 struct readahead_control {
 	struct file *file;
 	struct address_space *mapping;
+	struct file_ra_state *ra;
 /* private: use the readahead_* accessors instead */
 	pgoff_t _index;
 	unsigned int _nr_pages;
 	unsigned int _batch_count;
 };
 
-#define DEFINE_READAHEAD(rac, f, m, i)					\
-	struct readahead_control rac = {				\
+#define DEFINE_READAHEAD(ractl, f, r, m, i)				\
+	struct readahead_control ractl = {				\
 		.file = f,						\
 		.mapping = m,						\
+		.ra = r,						\
 		._index = i,						\
 	}
 
@@ -813,10 +836,11 @@ struct readahead_control {
 
 void page_cache_ra_unbounded(struct readahead_control *,
 		unsigned long nr_to_read, unsigned long lookahead_count);
-void page_cache_sync_ra(struct readahead_control *, struct file_ra_state *,
+void page_cache_sync_ra(struct readahead_control *, unsigned long req_count);
+void page_cache_async_ra(struct readahead_control *, struct page *,
 		unsigned long req_count);
-void page_cache_async_ra(struct readahead_control *, struct file_ra_state *,
-		struct page *, unsigned long req_count);
+void readahead_expand(struct readahead_control *ractl,
+		      loff_t new_start, size_t new_len);
 
 /**
  * page_cache_sync_readahead - generic file readahead
@@ -836,8 +860,8 @@ void page_cache_sync_readahead(struct address_space *mapping,
 		struct file_ra_state *ra, struct file *file, pgoff_t index,
 		unsigned long req_count)
 {
-	DEFINE_READAHEAD(ractl, file, mapping, index);
-	page_cache_sync_ra(&ractl, ra, req_count);
+	DEFINE_READAHEAD(ractl, file, ra, mapping, index);
+	page_cache_sync_ra(&ractl, req_count);
 }
 
 /**
@@ -859,8 +883,8 @@ void page_cache_async_readahead(struct address_space *mapping,
 		struct file_ra_state *ra, struct file *file,
 		struct page *page, pgoff_t index, unsigned long req_count)
 {
-	DEFINE_READAHEAD(ractl, file, mapping, index);
-	page_cache_async_ra(&ractl, ra, page, req_count);
+	DEFINE_READAHEAD(ractl, file, ra, mapping, index);
+	page_cache_async_ra(&ractl, page, req_count);
 }
 
 /**

include/linux/uio.h

@@ -24,6 +24,7 @@ enum iter_type {
 	ITER_BVEC = 16,
 	ITER_PIPE = 32,
 	ITER_DISCARD = 64,
+	ITER_XARRAY = 128,
 };
 
 struct iov_iter {
@@ -39,6 +40,7 @@ struct iov_iter {
 		const struct iovec *iov;
 		const struct kvec *kvec;
 		const struct bio_vec *bvec;
+		struct xarray *xarray;
 		struct pipe_inode_info *pipe;
 	};
 	union {
@@ -47,6 +49,7 @@ struct iov_iter {
 			unsigned int head;
 			unsigned int start_head;
 		};
+		loff_t xarray_start;
 	};
 };
 
@@ -80,6 +83,11 @@ static inline bool iov_iter_is_discard(const struct iov_iter *i)
 	return iov_iter_type(i) == ITER_DISCARD;
 }
 
+static inline bool iov_iter_is_xarray(const struct iov_iter *i)
+{
+	return iov_iter_type(i) == ITER_XARRAY;
+}
+
 static inline unsigned char iov_iter_rw(const struct iov_iter *i)
 {
 	return i->type & (READ | WRITE);
@@ -221,6 +229,8 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_
 void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
 			size_t count);
 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
+void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
+		     loff_t start, size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 			size_t maxsize, unsigned maxpages, size_t *start);
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,

include/trace/events/netfs.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Network filesystem support module tracepoints
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM netfs
+
+#if !defined(_TRACE_NETFS_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NETFS_H
+
+#include <linux/tracepoint.h>
+
+/*
+ * Define enums for tracing information.
+ */
+#ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
+#define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
+
+enum netfs_read_trace {
+	netfs_read_trace_expanded,
+	netfs_read_trace_readahead,
+	netfs_read_trace_readpage,
+	netfs_read_trace_write_begin,
+};
+
+enum netfs_rreq_trace {
+	netfs_rreq_trace_assess,
+	netfs_rreq_trace_done,
+	netfs_rreq_trace_free,
+	netfs_rreq_trace_resubmit,
+	netfs_rreq_trace_unlock,
+	netfs_rreq_trace_unmark,
+	netfs_rreq_trace_write,
+};
+
+enum netfs_sreq_trace {
+	netfs_sreq_trace_download_instead,
+	netfs_sreq_trace_free,
+	netfs_sreq_trace_prepare,
+	netfs_sreq_trace_resubmit_short,
+	netfs_sreq_trace_submit,
+	netfs_sreq_trace_terminated,
+	netfs_sreq_trace_write,
+	netfs_sreq_trace_write_skip,
+	netfs_sreq_trace_write_term,
+};
+
+enum netfs_failure {
+	netfs_fail_check_write_begin,
+	netfs_fail_copy_to_cache,
+	netfs_fail_read,
+	netfs_fail_short_readpage,
+	netfs_fail_short_write_begin,
+	netfs_fail_prepare_write,
+};
+
+#endif
+
+#define netfs_read_traces					\
+	EM(netfs_read_trace_expanded,		"EXPANDED ")	\
+	EM(netfs_read_trace_readahead,		"READAHEAD")	\
+	EM(netfs_read_trace_readpage,		"READPAGE ")	\
+	E_(netfs_read_trace_write_begin,	"WRITEBEGN")
+
+#define netfs_rreq_traces					\
+	EM(netfs_rreq_trace_assess,		"ASSESS")	\
+	EM(netfs_rreq_trace_done,		"DONE  ")	\
+	EM(netfs_rreq_trace_free,		"FREE  ")	\
+	EM(netfs_rreq_trace_resubmit,		"RESUBM")	\
+	EM(netfs_rreq_trace_unlock,		"UNLOCK")	\
+	EM(netfs_rreq_trace_unmark,		"UNMARK")	\
+	E_(netfs_rreq_trace_write,		"WRITE ")
+
+#define netfs_sreq_sources					\
+	EM(NETFS_FILL_WITH_ZEROES,		"ZERO")		\
+	EM(NETFS_DOWNLOAD_FROM_SERVER,		"DOWN")		\
+	EM(NETFS_READ_FROM_CACHE,		"READ")		\
+	E_(NETFS_INVALID_READ,			"INVL")		\
+
+#define netfs_sreq_traces					\
+	EM(netfs_sreq_trace_download_instead,	"RDOWN")	\
+	EM(netfs_sreq_trace_free,		"FREE ")	\
+	EM(netfs_sreq_trace_prepare,		"PREP ")	\
+	EM(netfs_sreq_trace_resubmit_short,	"SHORT")	\
+	EM(netfs_sreq_trace_submit,		"SUBMT")	\
+	EM(netfs_sreq_trace_terminated,		"TERM ")	\
+	EM(netfs_sreq_trace_write,		"WRITE")	\
+	EM(netfs_sreq_trace_write_skip,		"SKIP ")	\
+	E_(netfs_sreq_trace_write_term,		"WTERM")
+
+#define netfs_failures							\
+	EM(netfs_fail_check_write_begin,	"check-write-begin")	\
+	EM(netfs_fail_copy_to_cache,		"copy-to-cache")	\
+	EM(netfs_fail_read,			"read")			\
+	EM(netfs_fail_short_readpage,		"short-readpage")	\
+	EM(netfs_fail_short_write_begin,	"short-write-begin")	\
+	E_(netfs_fail_prepare_write,		"prep-write")
+
+
+/*
+ * Export enum symbols via userspace.
+ */
+#undef EM
+#undef E_
+#define EM(a, b) TRACE_DEFINE_ENUM(a);
+#define E_(a, b) TRACE_DEFINE_ENUM(a);
+
+netfs_read_traces;
+netfs_rreq_traces;
+netfs_sreq_sources;
+netfs_sreq_traces;
+netfs_failures;
+
+/*
+ * Now redefine the EM() and E_() macros to map the enums to the strings that
+ * will be printed in the output.
+ */
+#undef EM
+#undef E_
+#define EM(a, b)	{ a, b },
+#define E_(a, b)	{ a, b }
+
+TRACE_EVENT(netfs_read,
+	    TP_PROTO(struct netfs_read_request *rreq,
+		     loff_t start, size_t len,
+		     enum netfs_read_trace what),
+
+	    TP_ARGS(rreq, start, len, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned int,		cookie		)
+		    __field(loff_t,			start		)
+		    __field(size_t,			len		)
+		    __field(enum netfs_read_trace,	what		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->cookie	= rreq->cookie_debug_id;
+		    __entry->start	= start;
+		    __entry->len	= len;
+		    __entry->what	= what;
+			   ),
+
+	    TP_printk("R=%08x %s c=%08x s=%llx %zx",
+		      __entry->rreq,
+		      __print_symbolic(__entry->what, netfs_read_traces),
+		      __entry->cookie,
+		      __entry->start, __entry->len)
+	    );
+
+TRACE_EVENT(netfs_rreq,
+	    TP_PROTO(struct netfs_read_request *rreq,
+		     enum netfs_rreq_trace what),
+
+	    TP_ARGS(rreq, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned short,		flags		)
+		    __field(enum netfs_rreq_trace,	what		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->flags	= rreq->flags;
+		    __entry->what	= what;
+			   ),
+
+	    TP_printk("R=%08x %s f=%02x",
+		      __entry->rreq,
+		      __print_symbolic(__entry->what, netfs_rreq_traces),
+		      __entry->flags)
+	    );
+
+TRACE_EVENT(netfs_sreq,
+	    TP_PROTO(struct netfs_read_subrequest *sreq,
+		     enum netfs_sreq_trace what),
+
+	    TP_ARGS(sreq, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned short,		index		)
+		    __field(short,			error		)
+		    __field(unsigned short,		flags		)
+		    __field(enum netfs_read_source,	source		)
+		    __field(enum netfs_sreq_trace,	what		)
+		    __field(size_t,			len		)
+		    __field(size_t,			transferred	)
+		    __field(loff_t,			start		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= sreq->rreq->debug_id;
+		    __entry->index	= sreq->debug_index;
+		    __entry->error	= sreq->error;
+		    __entry->flags	= sreq->flags;
+		    __entry->source	= sreq->source;
+		    __entry->what	= what;
+		    __entry->len	= sreq->len;
+		    __entry->transferred = sreq->transferred;
+		    __entry->start	= sreq->start;
+			   ),
+
+	    TP_printk("R=%08x[%u] %s %s f=%02x s=%llx %zx/%zx e=%d",
+		      __entry->rreq, __entry->index,
+		      __print_symbolic(__entry->what, netfs_sreq_traces),
+		      __print_symbolic(__entry->source, netfs_sreq_sources),
+		      __entry->flags,
+		      __entry->start, __entry->transferred, __entry->len,
+		      __entry->error)
+	    );
+
+TRACE_EVENT(netfs_failure,
+	    TP_PROTO(struct netfs_read_request *rreq,
+		     struct netfs_read_subrequest *sreq,
+		     int error, enum netfs_failure what),
+
+	    TP_ARGS(rreq, sreq, error, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned short,		index		)
+		    __field(short,			error		)
+		    __field(unsigned short,		flags		)
+		    __field(enum netfs_read_source,	source		)
+		    __field(enum netfs_failure,		what		)
+		    __field(size_t,			len		)
+		    __field(size_t,			transferred	)
+		    __field(loff_t,			start		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->index	= sreq ? sreq->debug_index : 0;
+		    __entry->error	= error;
+		    __entry->flags	= sreq ? sreq->flags : 0;
+		    __entry->source	= sreq ? sreq->source : NETFS_INVALID_READ;
+		    __entry->what	= what;
+		    __entry->len	= sreq ? sreq->len : 0;
+		    __entry->transferred = sreq ? sreq->transferred : 0;
+		    __entry->start	= sreq ? sreq->start : 0;
+			   ),
+
+	    TP_printk("R=%08x[%u] %s f=%02x s=%llx %zx/%zx %s e=%d",
+		      __entry->rreq, __entry->index,
+		      __print_symbolic(__entry->source, netfs_sreq_sources),
+		      __entry->flags,
+		      __entry->start, __entry->transferred, __entry->len,
+		      __print_symbolic(__entry->what, netfs_failures),
+		      __entry->error)
+	    );
+
+#endif /* _TRACE_NETFS_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

mm/filemap.c

@@ -1432,6 +1432,67 @@ void unlock_page(struct page *page)
 }
 EXPORT_SYMBOL(unlock_page);
 
+/**
+ * end_page_private_2 - Clear PG_private_2 and release any waiters
+ * @page: The page
+ *
+ * Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
+ * this.  The page ref held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+void end_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	VM_BUG_ON_PAGE(!PagePrivate2(page), page);
+	clear_bit_unlock(PG_private_2, &page->flags);
+	wake_up_page_bit(page, PG_private_2);
+	put_page(page);
+}
+EXPORT_SYMBOL(end_page_private_2);
+
+/**
+ * wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
+ */
+void wait_on_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	while (PagePrivate2(page))
+		wait_on_page_bit(page, PG_private_2);
+}
+EXPORT_SYMBOL(wait_on_page_private_2);
+
+/**
+ * wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+int wait_on_page_private_2_killable(struct page *page)
+{
+	int ret = 0;
+
+	page = compound_head(page);
+	while (PagePrivate2(page)) {
+		ret = wait_on_page_bit_killable(page, PG_private_2);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(wait_on_page_private_2_killable);
+
 /**
  * end_page_writeback - end writeback against a page
  * @page: the page
@@ -2778,7 +2839,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 	struct file *file = vmf->vma->vm_file;
 	struct file_ra_state *ra = &file->f_ra;
 	struct address_space *mapping = file->f_mapping;
-	DEFINE_READAHEAD(ractl, file, mapping, vmf->pgoff);
+	DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
 	struct file *fpin = NULL;
 	unsigned int mmap_miss;
 
@@ -2790,7 +2851,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 
 	if (vmf->vma->vm_flags & VM_SEQ_READ) {
 		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
-		page_cache_sync_ra(&ractl, ra, ra->ra_pages);
+		page_cache_sync_ra(&ractl, ra->ra_pages);
 		return fpin;
 	}
 

mm/internal.h

@@ -51,13 +51,12 @@ void unmap_page_range(struct mmu_gather *tlb,
 
 void do_page_cache_ra(struct readahead_control *, unsigned long nr_to_read,
 		unsigned long lookahead_size);
-void force_page_cache_ra(struct readahead_control *, struct file_ra_state *,
-		unsigned long nr);
+void force_page_cache_ra(struct readahead_control *, unsigned long nr);
 static inline void force_page_cache_readahead(struct address_space *mapping,
 		struct file *file, pgoff_t index, unsigned long nr_to_read)
 {
-	DEFINE_READAHEAD(ractl, file, mapping, index);
-	force_page_cache_ra(&ractl, &file->f_ra, nr_to_read);
+	DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, index);
+	force_page_cache_ra(&ractl, nr_to_read);
 }
 
 unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,

mm/readahead.c

@@ -198,8 +198,6 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 	for (i = 0; i < nr_to_read; i++) {
 		struct page *page = xa_load(&mapping->i_pages, index + i);
 
-		BUG_ON(index + i != ractl->_index + ractl->_nr_pages);
-
 		if (page && !xa_is_value(page)) {
 			/*
 			 * Page already present?  Kick off the current batch
@@ -210,6 +208,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 			 * not worth getting one just for that.
 			 */
 			read_pages(ractl, &page_pool, true);
+			i = ractl->_index + ractl->_nr_pages - index - 1;
 			continue;
 		}
 
@@ -223,6 +222,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 					gfp_mask) < 0) {
 			put_page(page);
 			read_pages(ractl, &page_pool, true);
+			i = ractl->_index + ractl->_nr_pages - index - 1;
 			continue;
 		}
 		if (i == nr_to_read - lookahead_size)
@@ -272,9 +272,10 @@ void do_page_cache_ra(struct readahead_control *ractl,
  * memory at once.
  */
 void force_page_cache_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, unsigned long nr_to_read)
+		unsigned long nr_to_read)
 {
 	struct address_space *mapping = ractl->mapping;
+	struct file_ra_state *ra = ractl->ra;
 	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
 	unsigned long max_pages, index;
 
@@ -433,10 +434,10 @@ static int try_context_readahead(struct address_space *mapping,
  * A minimal readahead algorithm for trivial sequential/random reads.
  */
 static void ondemand_readahead(struct readahead_control *ractl,
-		struct file_ra_state *ra, bool hit_readahead_marker,
-		unsigned long req_size)
+		bool hit_readahead_marker, unsigned long req_size)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
+	struct file_ra_state *ra = ractl->ra;
 	unsigned long max_pages = ra->ra_pages;
 	unsigned long add_pages;
 	unsigned long index = readahead_index(ractl);
@@ -550,7 +551,7 @@ static void ondemand_readahead(struct readahead_control *ractl,
 }
 
 void page_cache_sync_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, unsigned long req_count)
+		unsigned long req_count)
 {
 	bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
 
@@ -560,7 +561,7 @@ void page_cache_sync_ra(struct readahead_control *ractl,
 	 * read-ahead will do the right thing and limit the read to just the
 	 * requested range, which we'll set to 1 page for this case.
 	 */
-	if (!ra->ra_pages || blk_cgroup_congested()) {
+	if (!ractl->ra->ra_pages || blk_cgroup_congested()) {
 		if (!ractl->file)
 			return;
 		req_count = 1;
@@ -569,21 +570,20 @@ void page_cache_sync_ra(struct readahead_control *ractl,
 
 	/* be dumb */
 	if (do_forced_ra) {
-		force_page_cache_ra(ractl, ra, req_count);
+		force_page_cache_ra(ractl, req_count);
 		return;
 	}
 
 	/* do read-ahead */
-	ondemand_readahead(ractl, ra, false, req_count);
+	ondemand_readahead(ractl, false, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_sync_ra);
 
 void page_cache_async_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, struct page *page,
-		unsigned long req_count)
+		struct page *page, unsigned long req_count)
 {
 	/* no read-ahead */
-	if (!ra->ra_pages)
+	if (!ractl->ra->ra_pages)
 		return;
 
 	/*
@@ -604,7 +604,7 @@ void page_cache_async_ra(struct readahead_control *ractl,
 		return;
 
 	/* do read-ahead */
-	ondemand_readahead(ractl, ra, true, req_count);
+	ondemand_readahead(ractl, true, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_async_ra);
 
@@ -638,3 +638,78 @@ SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
 {
 	return ksys_readahead(fd, offset, count);
 }
+
+/**
+ * readahead_expand - Expand a readahead request
+ * @ractl: The request to be expanded
+ * @new_start: The revised start
+ * @new_len: The revised size of the request
+ *
+ * Attempt to expand a readahead request outwards from the current size to the
+ * specified size by inserting locked pages before and after the current window
+ * to increase the size to the new window.  This may involve the insertion of
+ * THPs, in which case the window may get expanded even beyond what was
+ * requested.
+ *
+ * The algorithm will stop if it encounters a conflicting page already in the
+ * pagecache and leave a smaller expansion than requested.
+ *
+ * The caller must check for this by examining the revised @ractl object for a
+ * different expansion than was requested.
+ */
+void readahead_expand(struct readahead_control *ractl,
+		      loff_t new_start, size_t new_len)
+{
+	struct address_space *mapping = ractl->mapping;
+	struct file_ra_state *ra = ractl->ra;
+	pgoff_t new_index, new_nr_pages;
+	gfp_t gfp_mask = readahead_gfp_mask(mapping);
+
+	new_index = new_start / PAGE_SIZE;
+
+	/* Expand the leading edge downwards */
+	while (ractl->_index > new_index) {
+		unsigned long index = ractl->_index - 1;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+
+		ractl->_nr_pages++;
+		ractl->_index = page->index;
+	}
+
+	new_len += new_start - readahead_pos(ractl);
+	new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE);
+
+	/* Expand the trailing edge upwards */
+	while (ractl->_nr_pages < new_nr_pages) {
+		unsigned long index = ractl->_index + ractl->_nr_pages;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+		ractl->_nr_pages++;
+		if (ra) {
+			ra->size++;
+			ra->async_size++;
+		}
+	}
+}
+EXPORT_SYMBOL(readahead_expand);