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Commit 4b19de6d authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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mm: tiny-shmem nommu fix 



The previous patch db203d53 ("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: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6c1b7f68

fs/ramfs/file-nommu.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/ramfs.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

mm/tiny-shmem.c

+6 −0
Original line number Diff line number Diff line
@@ -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: