Commit b4caecd4 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

fs: introduce f_op->mmap_capabilities for nommu mmap support 



Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.

Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead.  Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device.  It also removes the need for
the mtd_inodefs filesystem.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarBrian Norris <computersforpeace@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 97b713ba

Documentation/nommu-mmap.txt

+4 −4
Original line number Diff line number Diff line
@@ -43,12 +43,12 @@ and it's also much more restricted in the latter case: 
           even if this was created by another process.



         - If possible, the file mapping will be directly on the backing device

           if the backing device has the BDI_CAP_MAP_DIRECT capability and

           if the backing device has the NOMMU_MAP_DIRECT capability and

           appropriate mapping protection capabilities. Ramfs, romfs, cramfs

           and mtd might all permit this.



	 - If the backing device device can't or won't permit direct sharing,

           but does have the BDI_CAP_MAP_COPY capability, then a copy of the

           but does have the NOMMU_MAP_COPY capability, then a copy of the

           appropriate bit of the file will be read into a contiguous bit of

           memory and any extraneous space beyond the EOF will be cleared
@@ -220,7 +220,7 @@ directly (can't be copied). 


The file->f_op->mmap() operation will be called to actually inaugurate the

mapping. It can be rejected at that point. Returning the ENOSYS error will

cause the mapping to be copied instead if BDI_CAP_MAP_COPY is specified.

cause the mapping to be copied instead if NOMMU_MAP_COPY is specified.



The vm_ops->close() routine will be invoked when the last mapping on a chardev

is removed. An existing mapping will be shared, partially or not, if possible
@@ -232,7 +232,7 @@ want to handle it, despite the fact it's got an operation. For instance, it 
might try directing the call to a secondary driver which turns out not to

implement it. Such is the case for the framebuffer driver which attempts to

direct the call to the device-specific driver. Under such circumstances, the

mapping request will be rejected if BDI_CAP_MAP_COPY is not specified, and a

mapping request will be rejected if NOMMU_MAP_COPY is not specified, and a

copy mapped otherwise.



IMPORTANT NOTE:

block/blk-core.c

+1 −1
Original line number Diff line number Diff line
@@ -607,7 +607,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) 
	q->backing_dev_info.ra_pages =

			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;

	q->backing_dev_info.state = 0;

	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;

	q->backing_dev_info.capabilities = 0;

	q->backing_dev_info.name = "block";

	q->node = node_id;

drivers/char/mem.c

+32 −32
Original line number Diff line number Diff line
@@ -287,13 +287,24 @@ static unsigned long get_unmapped_area_mem(struct file *file, 
	return pgoff << PAGE_SHIFT;

}



/* permit direct mmap, for read, write or exec */

static unsigned memory_mmap_capabilities(struct file *file)

{

	return NOMMU_MAP_DIRECT |

		NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;

}



static unsigned zero_mmap_capabilities(struct file *file)

{

	return NOMMU_MAP_COPY;

}



/* can't do an in-place private mapping if there's no MMU */

static inline int private_mapping_ok(struct vm_area_struct *vma)

{

	return vma->vm_flags & VM_MAYSHARE;

}

#else

#define get_unmapped_area_mem	NULL



static inline int private_mapping_ok(struct vm_area_struct *vma)

{
@@ -721,7 +732,10 @@ static const struct file_operations mem_fops = { 
	.write		= write_mem,

	.mmap		= mmap_mem,

	.open		= open_mem,

#ifndef CONFIG_MMU

	.get_unmapped_area = get_unmapped_area_mem,

	.mmap_capabilities = memory_mmap_capabilities,

#endif

};



#ifdef CONFIG_DEVKMEM
@@ -731,7 +745,10 @@ static const struct file_operations kmem_fops = { 
	.write		= write_kmem,

	.mmap		= mmap_kmem,

	.open		= open_kmem,

#ifndef CONFIG_MMU

	.get_unmapped_area = get_unmapped_area_mem,

	.mmap_capabilities = memory_mmap_capabilities,

#endif

};

#endif
@@ -760,16 +777,9 @@ static const struct file_operations zero_fops = { 
	.read_iter	= read_iter_zero,

	.aio_write	= aio_write_zero,

	.mmap		= mmap_zero,

};



/*

 * capabilities for /dev/zero

 * - permits private mappings, "copies" are taken of the source of zeros

 * - no writeback happens

 */

static struct backing_dev_info zero_bdi = {

	.name		= "char/mem",

	.capabilities	= BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,

#ifndef CONFIG_MMU

	.mmap_capabilities = zero_mmap_capabilities,

#endif

};



static const struct file_operations full_fops = {
@@ -783,22 +793,22 @@ static const struct memdev { 
	const char *name;

	umode_t mode;

	const struct file_operations *fops;

	struct backing_dev_info *dev_info;

	fmode_t fmode;

} devlist[] = {

	 [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },

	 [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },

#ifdef CONFIG_DEVKMEM

	 [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },

	 [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },

#endif

	 [3] = { "null", 0666, &null_fops, NULL },

	 [3] = { "null", 0666, &null_fops, 0 },

#ifdef CONFIG_DEVPORT

	 [4] = { "port", 0, &port_fops, NULL },

	 [4] = { "port", 0, &port_fops, 0 },

#endif

	 [5] = { "zero", 0666, &zero_fops, &zero_bdi },

	 [7] = { "full", 0666, &full_fops, NULL },

	 [8] = { "random", 0666, &random_fops, NULL },

	 [9] = { "urandom", 0666, &urandom_fops, NULL },

	 [5] = { "zero", 0666, &zero_fops, 0 },

	 [7] = { "full", 0666, &full_fops, 0 },

	 [8] = { "random", 0666, &random_fops, 0 },

	 [9] = { "urandom", 0666, &urandom_fops, 0 },

#ifdef CONFIG_PRINTK

	[11] = { "kmsg", 0644, &kmsg_fops, NULL },

	[11] = { "kmsg", 0644, &kmsg_fops, 0 },

#endif

};
@@ -816,12 +826,7 @@ static int memory_open(struct inode *inode, struct file *filp) 
		return -ENXIO;



	filp->f_op = dev->fops;

	if (dev->dev_info)

		filp->f_mapping->backing_dev_info = dev->dev_info;



	/* Is /dev/mem or /dev/kmem ? */

	if (dev->dev_info == &directly_mappable_cdev_bdi)

		filp->f_mode |= FMODE_UNSIGNED_OFFSET;

	filp->f_mode |= dev->fmode;



	if (dev->fops->open)

		return dev->fops->open(inode, filp);
@@ -846,11 +851,6 @@ static struct class *mem_class; 
static int __init chr_dev_init(void)

{

	int minor;

	int err;



	err = bdi_init(&zero_bdi);

	if (err)

		return err;



	if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))

		printk("unable to get major %d for memory devs\n", MEM_MAJOR);

drivers/mtd/mtdchar.c

+10 −62
Original line number Diff line number Diff line
@@ -49,7 +49,6 @@ static DEFINE_MUTEX(mtd_mutex); 
 */

struct mtd_file_info {

	struct mtd_info *mtd;

	struct inode *ino;

	enum mtd_file_modes mode;

};
@@ -59,10 +58,6 @@ static loff_t mtdchar_lseek(struct file *file, loff_t offset, int orig) 
	return fixed_size_llseek(file, offset, orig, mfi->mtd->size);

}



static int count;

static struct vfsmount *mnt;

static struct file_system_type mtd_inodefs_type;



static int mtdchar_open(struct inode *inode, struct file *file)

{

	int minor = iminor(inode);
@@ -70,7 +65,6 @@ static int mtdchar_open(struct inode *inode, struct file *file) 
	int ret = 0;

	struct mtd_info *mtd;

	struct mtd_file_info *mfi;

	struct inode *mtd_ino;



	pr_debug("MTD_open\n");
@@ -78,10 +72,6 @@ static int mtdchar_open(struct inode *inode, struct file *file) 
	if ((file->f_mode & FMODE_WRITE) && (minor & 1))

		return -EACCES;



	ret = simple_pin_fs(&mtd_inodefs_type, &mnt, &count);

	if (ret)

		return ret;



	mutex_lock(&mtd_mutex);

	mtd = get_mtd_device(NULL, devnum);
@@ -95,43 +85,26 @@ static int mtdchar_open(struct inode *inode, struct file *file) 
		goto out1;

	}



	mtd_ino = iget_locked(mnt->mnt_sb, devnum);

	if (!mtd_ino) {

		ret = -ENOMEM;

		goto out1;

	}

	if (mtd_ino->i_state & I_NEW) {

		mtd_ino->i_private = mtd;

		mtd_ino->i_mode = S_IFCHR;

		mtd_ino->i_data.backing_dev_info = mtd->backing_dev_info;

		unlock_new_inode(mtd_ino);

	}

	file->f_mapping = mtd_ino->i_mapping;



	/* You can't open it RW if it's not a writeable device */

	if ((file->f_mode & FMODE_WRITE) && !(mtd->flags & MTD_WRITEABLE)) {

		ret = -EACCES;

		goto out2;

		goto out1;

	}



	mfi = kzalloc(sizeof(*mfi), GFP_KERNEL);

	if (!mfi) {

		ret = -ENOMEM;

		goto out2;

		goto out1;

	}

	mfi->ino = mtd_ino;

	mfi->mtd = mtd;

	file->private_data = mfi;

	mutex_unlock(&mtd_mutex);

	return 0;



out2:

	iput(mtd_ino);

out1:

	put_mtd_device(mtd);

out:

	mutex_unlock(&mtd_mutex);

	simple_release_fs(&mnt, &count);

	return ret;

} /* mtdchar_open */
@@ -148,12 +121,9 @@ static int mtdchar_close(struct inode *inode, struct file *file) 
	if ((file->f_mode & FMODE_WRITE))

		mtd_sync(mtd);



	iput(mfi->ino);



	put_mtd_device(mtd);

	file->private_data = NULL;

	kfree(mfi);

	simple_release_fs(&mnt, &count);



	return 0;

} /* mtdchar_close */
@@ -1117,6 +1087,13 @@ static unsigned long mtdchar_get_unmapped_area(struct file *file, 
	ret = mtd_get_unmapped_area(mtd, len, offset, flags);

	return ret == -EOPNOTSUPP ? -ENODEV : ret;

}



static unsigned mtdchar_mmap_capabilities(struct file *file)

{

	struct mtd_file_info *mfi = file->private_data;



	return mtd_mmap_capabilities(mfi->mtd);

}

#endif



/*
@@ -1160,27 +1137,10 @@ static const struct file_operations mtd_fops = { 
	.mmap		= mtdchar_mmap,

#ifndef CONFIG_MMU

	.get_unmapped_area = mtdchar_get_unmapped_area,

	.mmap_capabilities = mtdchar_mmap_capabilities,

#endif

};



static const struct super_operations mtd_ops = {

	.drop_inode = generic_delete_inode,

	.statfs = simple_statfs,

};



static struct dentry *mtd_inodefs_mount(struct file_system_type *fs_type,

				int flags, const char *dev_name, void *data)

{

	return mount_pseudo(fs_type, "mtd_inode:", &mtd_ops, NULL, MTD_INODE_FS_MAGIC);

}



static struct file_system_type mtd_inodefs_type = {

       .name = "mtd_inodefs",

       .mount = mtd_inodefs_mount,

       .kill_sb = kill_anon_super,

};

MODULE_ALIAS_FS("mtd_inodefs");



int __init init_mtdchar(void)

{

	int ret;
@@ -1193,23 +1153,11 @@ int __init init_mtdchar(void) 
		return ret;

	}



	ret = register_filesystem(&mtd_inodefs_type);

	if (ret) {

		pr_err("Can't register mtd_inodefs filesystem, error %d\n",

		       ret);

		goto err_unregister_chdev;

	}



	return ret;



err_unregister_chdev:

	__unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd");

	return ret;

}



void __exit cleanup_mtdchar(void)

{

	unregister_filesystem(&mtd_inodefs_type);

	__unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd");

}

drivers/mtd/mtdconcat.c

+0 −10
Original line number Diff line number Diff line
@@ -732,8 +732,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c 


	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;



	concat->mtd.backing_dev_info = subdev[0]->backing_dev_info;



	concat->subdev[0] = subdev[0];



	for (i = 1; i < num_devs; i++) {
@@ -761,14 +759,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c 
				    subdev[i]->flags & MTD_WRITEABLE;

		}



		/* only permit direct mapping if the BDIs are all the same

		 * - copy-mapping is still permitted

		 */

		if (concat->mtd.backing_dev_info !=

		    subdev[i]->backing_dev_info)

			concat->mtd.backing_dev_info =

				&default_backing_dev_info;



		concat->mtd.size += subdev[i]->size;

		concat->mtd.ecc_stats.badblocks +=

			subdev[i]->ecc_stats.badblocks;

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