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https://github.com/torvalds/linux
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b4caecd480
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>
90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
/* NOMMU mmap support for RomFS on MTD devices
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*
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* Copyright © 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/mm.h>
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#include <linux/mtd/super.h>
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#include "internal.h"
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/*
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* try to determine where a shared mapping can be made
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* - only supported for NOMMU at the moment (MMU can't doesn't copy private
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* mappings)
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* - attempts to map through to the underlying MTD device
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*/
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static unsigned long romfs_get_unmapped_area(struct file *file,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags)
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{
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struct inode *inode = file->f_mapping->host;
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struct mtd_info *mtd = inode->i_sb->s_mtd;
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unsigned long isize, offset, maxpages, lpages;
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int ret;
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if (!mtd)
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return (unsigned long) -ENOSYS;
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/* the mapping mustn't extend beyond the EOF */
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lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
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isize = i_size_read(inode);
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offset = pgoff << PAGE_SHIFT;
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maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
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if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
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return (unsigned long) -EINVAL;
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if (addr != 0)
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return (unsigned long) -EINVAL;
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if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
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return (unsigned long) -EINVAL;
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offset += ROMFS_I(inode)->i_dataoffset;
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if (offset >= mtd->size)
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return (unsigned long) -EINVAL;
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/* the mapping mustn't extend beyond the EOF */
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if ((offset + len) > mtd->size)
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len = mtd->size - offset;
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ret = mtd_get_unmapped_area(mtd, len, offset, flags);
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if (ret == -EOPNOTSUPP)
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ret = -ENOSYS;
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return (unsigned long) ret;
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}
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/*
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* permit a R/O mapping to be made directly through onto an MTD device if
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* possible
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*/
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static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
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{
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return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
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}
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static unsigned romfs_mmap_capabilities(struct file *file)
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{
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struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
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if (!mtd)
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return NOMMU_MAP_COPY;
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return mtd_mmap_capabilities(mtd);
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}
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const struct file_operations romfs_ro_fops = {
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.llseek = generic_file_llseek,
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.read = new_sync_read,
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.read_iter = generic_file_read_iter,
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.splice_read = generic_file_splice_read,
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.mmap = romfs_mmap,
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.get_unmapped_area = romfs_get_unmapped_area,
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.mmap_capabilities = romfs_mmap_capabilities,
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};
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