mm: tiny-shmem nommu fix (4b19de6d) · Commits · 戴 / test

The previous patch ("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

+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:

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