From 4b19de6d1cb07c8bcb6778e771f9cfd5bcfdfd3e Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@suse.de>
Date: Thu, 2 Oct 2008 14:50:16 -0700
Subject: [PATCH] mm: tiny-shmem nommu fix
The previous patch db203d53d474aa068984e409d807628f5841da1b ("mm:
tiny-shmem fix lock ordering: mmap_sem vs i_mutex") to fix the lock
ordering in tiny-shmem breaks shared anonymous and IPC memory on NOMMU
architectures because it was using the expanding truncate to signal ramfs
to allocate a physically contiguous RAM backing the inode (otherwise it is
unusable for "memory mapping" it to userspace).
However do_truncate is what caused the lock ordering error, due to it
taking i_mutex. In this case, we can actually just call ramfs directly to
allocate memory for the mapping, rather than go via truncate.
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/ramfs/file-nommu.c | 2 +-
include/linux/ramfs.h | 1 +
mm/tiny-shmem.c | 6 ++++++
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index 52312ec93ff..5145cb9125a 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -58,7 +58,7 @@ const struct inode_operations ramfs_file_inode_operations = {
* size 0 on the assumption that it's going to be used for an mmap of shared
* memory
*/
-static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
+int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
{
struct pagevec lru_pvec;
unsigned long npages, xpages, loop, limit;
diff --git a/include/linux/ramfs.h b/include/linux/ramfs.h
index b160fb18e8d..37aaf2b3986 100644
--- a/include/linux/ramfs.h
+++ b/include/linux/ramfs.h
@@ -6,6 +6,7 @@ extern int ramfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt);
#ifndef CONFIG_MMU
+extern int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize);
extern unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
unsigned long addr,
unsigned long len,
diff --git a/mm/tiny-shmem.c b/mm/tiny-shmem.c
index d17cb6f6ab1..8d7a27a6335 100644
--- a/mm/tiny-shmem.c
+++ b/mm/tiny-shmem.c
@@ -80,6 +80,12 @@ struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
inode->i_nlink = 0; /* It is unlinked */
init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
&ramfs_file_operations);
+
+#ifndef CONFIG_MMU
+ error = ramfs_nommu_expand_for_mapping(inode, size);
+ if (error)
+ goto close_file;
+#endif
return file;
close_file:
--
2.41.3