linux-kernel - [patch 2/3] fuse: allow private mappings of "direct

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Message-Id: <E1LoNhP-0007lc-FC@pomaz-ex.szeredi.hu>
Date:	Mon, 30 Mar 2009 22:03:11 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	linux-fsdevel@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: [patch 2/3] fuse: allow private mappings of "direct_io" files

From: Miklos Szeredi <mszeredi@...e.cz>

Allow MAP_PRIVATE mmaps of "direct_io" files.  This is necessary for
execute support.

MAP_SHARED mappings require some sort of coherency between the
underlying file and the mapping.  With "direct_io" it is difficult to
provide this, so for the moment just disallow shared (read-write and
read-only) mappings altogether.

Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
 fs/fuse/file.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-2.6/fs/fuse/file.c
===================================================================
--- linux-2.6.orig/fs/fuse/file.c	2009-03-30 18:47:55.000000000 +0200
+++ linux-2.6/fs/fuse/file.c	2009-03-30 19:07:11.000000000 +0200
@@ -1291,6 +1291,15 @@ static int fuse_file_mmap(struct file *f
 	return 0;
 }
 
+static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	/* Can't provide the coherency needed for MAP_SHARED */
+	if (vma->vm_flags & VM_MAYSHARE)
+		return -ENODEV;
+
+	return generic_file_mmap(file, vma);
+}
+
 static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
 				  struct file_lock *fl)
 {
@@ -1925,6 +1934,7 @@ static const struct file_operations fuse
 	.llseek		= fuse_file_llseek,
 	.read		= fuse_direct_read,
 	.write		= fuse_direct_write,
+	.mmap		= fuse_direct_mmap,
 	.open		= fuse_open,
 	.flush		= fuse_flush,
 	.release	= fuse_release,
@@ -1934,7 +1944,7 @@ static const struct file_operations fuse
 	.unlocked_ioctl	= fuse_file_ioctl,
 	.compat_ioctl	= fuse_file_compat_ioctl,
 	.poll		= fuse_file_poll,
-	/* no mmap and splice_read */
+	/* no splice_read */
 };
 
 static const struct address_space_operations fuse_file_aops  = {
--
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