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ext4: Correct block number handling, empty block vs. error code

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read_allocated block may return block number 0, which is just an indicator
a chunk of the file is not backed by a block, i.e. it is sparse.

During file deletions, just continue with the next logical block, for other
operations treat blocknumber <= 0 as an error.

For writes, blocknumber 0 should never happen, as U-Boot always allocates
blocks for the whole file.  Reading already handles this correctly, i.e. the
read buffer is 0-fillled.

Not treating block 0 as sparse block leads to FS corruption, e.g.
	./sandbox/u-boot -c 'host bind 0 ./sandbox/test/fs/3GB.ext4.img ;
		ext4write host 0 0 /2.5GB.file 1 '
The 2.5GB.file from the fs test is actually a sparse file.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
This commit is contained in:
Stefan Brüns
2016-09-06 04:36:55 +02:00
committed by Tom Rini
parent b779e0290a
commit de9e831675
2 changed files with 13 additions and 4 deletions
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6
fs/ext4/ext4_common.c
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@@ -534,7 +534,7 @@ static int search_dir(struct ext2_inode *parent_inode, char *dirname)
/* get the block no allocated to a file */
for (blk_idx = 0; blk_idx < directory_blocks; blk_idx++) {
blknr = read_allocated_block(parent_inode, blk_idx);
if (blknr == 0)
if (blknr <= 0)
goto fail;
/* read the directory block */
@@ -828,7 +828,7 @@ int ext4fs_filename_unlink(char *filename)
/* read the block no allocated to a file */
for (blk_idx = 0; blk_idx < directory_blocks; blk_idx++) {
blknr = read_allocated_block(g_parent_inode, blk_idx);
if (blknr == 0)
if (blknr <= 0)
break;
inodeno = unlink_filename(filename, blknr);
if (inodeno != -1)
@@ -1590,7 +1590,7 @@ long int read_allocated_block(struct ext2_inode *inode, int fileblock)
if (status == 0) {
printf("** SI ext2fs read block (indir 1)"
"failed. **\n");
return 0;
return -1;
}
ext4fs_indir1_blkno =
le32_to_cpu(inode->b.blocks.