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libfs: Fix shift bug in generic_check_addressable()

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generic_check_addressable() erroneously shifts pages down by a block
factor when it should be shifting up.  To prevent overflow, we shift
blocks down to pages.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
This commit is contained in:
Joel Becker 2010-08-16 12:10:17 -07:00
parent 3bdb8efd94
commit a33f13efe0
1 changed files with 4 additions and 4 deletions
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8
fs/libfs.c
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@ -925,6 +925,8 @@ EXPORT_SYMBOL(generic_file_fsync);
int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
{
u64 last_fs_block = num_blocks - 1;
u64 last_fs_page =
last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
if (unlikely(num_blocks == 0))
return 0;
@ -932,10 +934,8 @@ int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
return -EINVAL;
if ((last_fs_block >
(sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
(last_fs_block >
(pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - blocksize_bits))) {
if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
(last_fs_page > (pgoff_t)(~0ULL))) {
return -EFBIG;
}
return 0;