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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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10
fs/romfs/mmap-nommu.c
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@@ -70,6 +70,15 @@ static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
}
static unsigned romfs_mmap_capabilities(struct file *file)
{
struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
if (!mtd)
return NOMMU_MAP_COPY;
return mtd_mmap_capabilities(mtd);
}
const struct file_operations romfs_ro_fops = {
.llseek = generic_file_llseek,
.read = new_sync_read,
@@ -77,4 +86,5 @@ const struct file_operations romfs_ro_fops = {
.splice_read = generic_file_splice_read,
.mmap = romfs_mmap,
.get_unmapped_area = romfs_get_unmapped_area,
.mmap_capabilities = romfs_mmap_capabilities,
};