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ext4: fix trimming starting with block 0 with small blocksize 

When s_first_data_block is not zero (which happens e.g. when block size is 1KB)
and trim ioctl is called to start trimming from block 0, the math in
ext4_get_group_no_and_offset() overflows. The overall result is that ioctl
returns EINVAL which is kind of unexpected and we probably don't want
userspace tools to bother with internal details of filesystem structure.
So just silently increase starting offset (and shorten length) when starting
block is below s_first_data_block.

CC: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2011-01-11 15:16:31 -05:00 committed by Theodore Ts'o
parent 0a2179b169
commit 0f0a25bf51
1 changed files with 6 additions and 0 deletions
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6
fs/ext4/mballoc.c
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@ -4808,6 +4808,8 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
ext4_group_t group, ngroups = ext4_get_groups_count(sb);
ext4_grpblk_t cnt = 0, first_block, last_block;
uint64_t start, len, minlen, trimmed;
ext4_fsblk_t first_data_blk =
le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
int ret = 0;
start = range->start >> sb->s_blocksize_bits;
@ -4817,6 +4819,10 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
return -EINVAL;
if (start < first_data_blk) {
len -= first_data_blk - start;
start = first_data_blk;
}
/* Determine first and last group to examine based on start and len */
ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) start,