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fs: introduce f_op->mmap_capabilities for nommu mmap support

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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
2015-01-14 10:42:32 +01:00
committed by Jens Axboe
parent 97b713ba3e
commit b4caecd480
32 changed files with 169 additions and 346 deletions
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64
drivers/char/mem.c
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@@ -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);