Commit 0d606e2c authored Apr 23, 2013 by Theodore Ts'o

ext4: fix type-widening bug in inode table readahead code



Due to a missing cast, the high 32-bits of a 64-bit block number used
when calculating the readahead block for inode tables can get lost.
This means we can end up fetching the wrong blocks for readahead for
file systems > 16TB.

Linus found this when experimenting with an enhacement to the sparse
static code checker which checks for missing widening casts before
binary "not" operators.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

parent 3f8a6411

fs/ext4/inode.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -4011,13 +4011,14 @@ make_io:
		if (EXT4_SB(sb)->s_inode_readahead_blks) {
		ext4_fsblk_t b, end, table;
		unsigned num;
		__u32 ra_blks = EXT4_SB(sb)->s_inode_readahead_blks;

		table = ext4_inode_table(sb, gdp);
		/* s_inode_readahead_blks is always a power of 2 */
		b = block & ~(EXT4_SB(sb)->s_inode_readahead_blks-1);
		b = block & ~((ext4_fsblk_t) ra_blks - 1);
		if (table > b)
		b = table;
		end = b + EXT4_SB(sb)->s_inode_readahead_blks;
		end = b + ra_blks;
		num = EXT4_INODES_PER_GROUP(sb);
		if (ext4_has_group_desc_csum(sb))
		num -= ext4_itable_unused_count(sb, gdp);