fs: ext4: fix writing zero-length files
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>
diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 1c11721..33d69c9 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -1380,7 +1380,7 @@
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 @@
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,