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Linux/fs/romfs/mmap-nommu.c

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  1 /* NOMMU mmap support for RomFS on MTD devices
  2  *
  3  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #include <linux/mm.h>
 13 #include <linux/mtd/super.h>
 14 #include "internal.h"
 15 
 16 /*
 17  * try to determine where a shared mapping can be made
 18  * - only supported for NOMMU at the moment (MMU can't doesn't copy private
 19  *   mappings)
 20  * - attempts to map through to the underlying MTD device
 21  */
 22 static unsigned long romfs_get_unmapped_area(struct file *file,
 23                                              unsigned long addr,
 24                                              unsigned long len,
 25                                              unsigned long pgoff,
 26                                              unsigned long flags)
 27 {
 28         struct inode *inode = file->f_mapping->host;
 29         struct mtd_info *mtd = inode->i_sb->s_mtd;
 30         unsigned long isize, offset, maxpages, lpages;
 31         int ret;
 32 
 33         if (!mtd)
 34                 return (unsigned long) -ENOSYS;
 35 
 36         /* the mapping mustn't extend beyond the EOF */
 37         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 38         isize = i_size_read(inode);
 39         offset = pgoff << PAGE_SHIFT;
 40 
 41         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 42         if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
 43                 return (unsigned long) -EINVAL;
 44 
 45         if (addr != 0)
 46                 return (unsigned long) -EINVAL;
 47 
 48         if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
 49                 return (unsigned long) -EINVAL;
 50 
 51         offset += ROMFS_I(inode)->i_dataoffset;
 52         if (offset >= mtd->size)
 53                 return (unsigned long) -EINVAL;
 54         /* the mapping mustn't extend beyond the EOF */
 55         if ((offset + len) > mtd->size)
 56                 len = mtd->size - offset;
 57 
 58         ret = mtd_get_unmapped_area(mtd, len, offset, flags);
 59         if (ret == -EOPNOTSUPP)
 60                 ret = -ENOSYS;
 61         return (unsigned long) ret;
 62 }
 63 
 64 /*
 65  * permit a R/O mapping to be made directly through onto an MTD device if
 66  * possible
 67  */
 68 static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
 69 {
 70         return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
 71 }
 72 
 73 static unsigned romfs_mmap_capabilities(struct file *file)
 74 {
 75         struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
 76 
 77         if (!mtd)
 78                 return NOMMU_MAP_COPY;
 79         return mtd_mmap_capabilities(mtd);
 80 }
 81 
 82 const struct file_operations romfs_ro_fops = {
 83         .llseek                 = generic_file_llseek,
 84         .read_iter              = generic_file_read_iter,
 85         .splice_read            = generic_file_splice_read,
 86         .mmap                   = romfs_mmap,
 87         .get_unmapped_area      = romfs_get_unmapped_area,
 88         .mmap_capabilities      = romfs_mmap_capabilities,
 89 };
 90 

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