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fs: ext4: fix writing zero-length files

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ext4fs_allocate_blocks() always allocates at least one block for a file.
If the file size is zero, this causes total_remaining_blocks to
underflow, which then causes an apparent hang while 2^32 blocks are
allocated.

To solve this, check that total_remaining_blocks is non-zero as part of
the loop condition (i.e. before each loop) rather than at the end of
the loop.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
This commit is contained in:
Stephen Warren 2014-06-11 12:46:16 -06:00 committed by Tom Rini
parent 50babaf852
commit d018028055
1 changed files with 1 additions and 3 deletions
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4
fs/ext4/ext4_common.c
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@ -1380,7 +1380,7 @@ void ext4fs_allocate_blocks(struct ext2_inode *file_inode,
unsigned int no_blks_reqd = 0;
/* allocation of direct blocks */
for (i = 0; i < INDIRECT_BLOCKS; i++) {
for (i = 0; total_remaining_blocks && i < INDIRECT_BLOCKS; i++) {
direct_blockno = ext4fs_get_new_blk_no();
if (direct_blockno == -1) {
printf("no block left to assign\n");
@ -1390,8 +1390,6 @@ void ext4fs_allocate_blocks(struct ext2_inode *file_inode,
debug("DB %ld: %u\n", direct_blockno, total_remaining_blocks);
total_remaining_blocks--;
if (total_remaining_blocks == 0)
break;
}
alloc_single_indirect_block(file_inode, &total_remaining_blocks,