[PATCH] fuse: more flexible caching

Make data caching behavior selectable on a per-open basis instead of
per-mount.  Compatibility for the old mount options 'kernel_cache' and
'direct_io' is retained in the userspace library (version 2.4.0-pre1 or
later).
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/filesystems/fuse.txt

@@ -80,32 +80,6 @@ Mount options
   allowed to root, but this restriction can be removed with a
   (userspace) configuration option.
 
-'kernel_cache'
-
-  This option disables flushing the cache of the file contents on
-  every open().  This should only be enabled on filesystems, where the
-  file data is never changed externally (not through the mounted FUSE
-  filesystem).  Thus it is not suitable for network filesystems and
-  other "intermediate" filesystems.
-
-  NOTE: if this option is not specified (and neither 'direct_io') data
-  is still cached after the open(), so a read() system call will not
-  always initiate a read operation.
-
-'direct_io'
-
-  This option disables the use of page cache (file content cache) in
-  the kernel for this filesystem.  This has several affects:
-
-     - Each read() or write() system call will initiate one or more
-       read or write operations, data will not be cached in the
-       kernel.
-
-     - The return value of the read() and write() system calls will
-       correspond to the return values of the read and write
-       operations.  This is useful for example if the file size is not
-       known in advance (before reading it).
-
 'max_read=N'
 
   With this option the maximum size of read operations can be set.

fs/fuse/file.c

@@ -12,6 +12,8 @@
 #include <linux/slab.h>
 #include <linux/kernel.h>
 
+static struct file_operations fuse_direct_io_file_operations;
+
 int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -70,12 +72,14 @@ int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 	else
 		request_send(fc, req);
 	err = req->out.h.error;
-	if (!err && !(fc->flags & FUSE_KERNEL_CACHE))
-		invalidate_inode_pages(inode->i_mapping);
 	if (err) {
 		fuse_request_free(ff->release_req);
 		kfree(ff);
 	} else {
+		if (!isdir && (outarg.open_flags & FOPEN_DIRECT_IO))
+			file->f_op = &fuse_direct_io_file_operations;
+		if (!(outarg.open_flags & FOPEN_KEEP_CACHE))
+			invalidate_inode_pages(inode->i_mapping);
 		ff->fh = outarg.fh;
 		file->private_data = ff;
 	}
@@ -544,12 +548,6 @@ static struct address_space_operations fuse_file_aops  = {
 
 void fuse_init_file_inode(struct inode *inode)
 {
-	struct fuse_conn *fc = get_fuse_conn(inode);
-
-	if (fc->flags & FUSE_DIRECT_IO)
-		inode->i_fop = &fuse_direct_io_file_operations;
-	else {
-		inode->i_fop = &fuse_file_operations;
-		inode->i_data.a_ops = &fuse_file_aops;
-	}
+	inode->i_fop = &fuse_file_operations;
+	inode->i_data.a_ops = &fuse_file_aops;
 }

fs/fuse/fuse_i.h

@@ -30,12 +30,6 @@
     doing the mount will be allowed to access the filesystem */
 #define FUSE_ALLOW_OTHER         (1 << 1)
 
-/** If the FUSE_KERNEL_CACHE flag is given, then cached data will not
-    be flushed on open */
-#define FUSE_KERNEL_CACHE        (1 << 2)
-
-/** Bypass the page cache for read and write operations  */
-#define FUSE_DIRECT_IO           (1 << 3)
 
 /** FUSE inode */
 struct fuse_inode {

fs/fuse/inode.c

@@ -257,8 +257,6 @@ enum {
 	OPT_GROUP_ID,
 	OPT_DEFAULT_PERMISSIONS,
 	OPT_ALLOW_OTHER,
-	OPT_KERNEL_CACHE,
-	OPT_DIRECT_IO,
 	OPT_MAX_READ,
 	OPT_ERR
 };
@@ -270,8 +268,6 @@ static match_table_t tokens = {
 	{OPT_GROUP_ID,			"group_id=%u"},
 	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
 	{OPT_ALLOW_OTHER,		"allow_other"},
-	{OPT_KERNEL_CACHE,		"kernel_cache"},
-	{OPT_DIRECT_IO,			"direct_io"},
 	{OPT_MAX_READ,			"max_read=%u"},
 	{OPT_ERR,			NULL}
 };
@@ -327,14 +323,6 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d)
 			d->flags |= FUSE_ALLOW_OTHER;
 			break;
 
-		case OPT_KERNEL_CACHE:
-			d->flags |= FUSE_KERNEL_CACHE;
-			break;
-
-		case OPT_DIRECT_IO:
-			d->flags |= FUSE_DIRECT_IO;
-			break;
-
 		case OPT_MAX_READ:
 			if (match_int(&args[0], &value))
 				return 0;
@@ -363,10 +351,6 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
 		seq_puts(m, ",default_permissions");
 	if (fc->flags & FUSE_ALLOW_OTHER)
 		seq_puts(m, ",allow_other");
-	if (fc->flags & FUSE_KERNEL_CACHE)
-		seq_puts(m, ",kernel_cache");
-	if (fc->flags & FUSE_DIRECT_IO)
-		seq_puts(m, ",direct_io");
 	if (fc->max_read != ~0)
 		seq_printf(m, ",max_read=%u", fc->max_read);
 	return 0;

include/linux/fuse.h

@@ -14,7 +14,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 1
+#define FUSE_KERNEL_MINOR_VERSION 2
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -63,6 +63,15 @@ struct fuse_kstatfs {
 #define FATTR_MTIME	(1 << 5)
 #define FATTR_CTIME	(1 << 6)
 
+/**
+ * Flags returned by the OPEN request
+ *
+ * FOPEN_DIRECT_IO: bypass page cache for this open file
+ * FOPEN_KEEP_CACHE: don't invalidate the data cache on open
+ */
+#define FOPEN_DIRECT_IO		(1 << 0)
+#define FOPEN_KEEP_CACHE	(1 << 1)
+
 enum fuse_opcode {
 	FUSE_LOOKUP	   = 1,
 	FUSE_FORGET	   = 2,  /* no reply */