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From a0ade1deb86d2325aecc36272bb4505a6eec9235 Mon Sep 17 00:00:00 2001
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From: Lukas Czerner <lczerner@redhat.com>
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Date: Mon, 20 Feb 2012 23:02:06 -0500
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Subject: [PATCH] ext4: fix resize when resizing within single group
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When resizing file system in the way that the new size of the file
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system is still in the same group (no new groups are added), then we can
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hit a BUG_ON in ext4_alloc_group_tables()
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BUG_ON(flex_gd->count == 0 || group_data == NULL);
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because flex_gd->count is zero. The reason is the missing check for such
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case, so the code always extend the last group fully and then attempt to
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add more groups, but at that time n_blocks_count is actually smaller
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than o_blocks_count.
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It can be easily reproduced like this:
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mkfs.ext4 -b 4096 /dev/sda 30M
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mount /dev/sda /mnt/test
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resize2fs /dev/sda 50M
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Fix this by checking whether the resize happens within the singe group
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and only add that many blocks into the last group to satisfy user
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request. Then o_blocks_count == n_blocks_count and the resize will exit
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successfully without and attempt to add more groups into the fs.
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Also fix mixing together block number and blocks count which might be
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confusing and can easily lead to off-by-one errors (but it is actually
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not the case here since the two occurrence of this mix-up will cancel
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each other).
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Signed-off-by: Lukas Czerner <lczerner@redhat.com>
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Reported-by: Milan Broz <mbroz@redhat.com>
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Reviewed-by: Eric Sandeen <sandeen@redhat.com>
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Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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---
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fs/ext4/resize.c | 14 ++++++++------
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1 files changed, 8 insertions(+), 6 deletions(-)
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diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
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index f9d948f..3fed79d 100644
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--- a/fs/ext4/resize.c
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+++ b/fs/ext4/resize.c
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@@ -1582,7 +1582,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
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ext4_fsblk_t o_blocks_count;
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ext4_group_t o_group;
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ext4_group_t n_group;
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- ext4_grpblk_t offset;
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+ ext4_grpblk_t offset, add;
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unsigned long n_desc_blocks;
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unsigned long o_desc_blocks;
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unsigned long desc_blocks;
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@@ -1605,7 +1605,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
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return 0;
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ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset);
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- ext4_get_group_no_and_offset(sb, o_blocks_count, &o_group, &offset);
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+ ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
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n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) /
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EXT4_DESC_PER_BLOCK(sb);
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@@ -1634,10 +1634,12 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
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}
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brelse(bh);
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- if (offset != 0) {
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- /* extend the last group */
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- ext4_grpblk_t add;
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- add = EXT4_BLOCKS_PER_GROUP(sb) - offset;
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+ /* extend the last group */
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+ if (n_group == o_group)
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+ add = n_blocks_count - o_blocks_count;
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+ else
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+ add = EXT4_BLOCKS_PER_GROUP(sb) - (offset + 1);
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+ if (add > 0) {
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err = ext4_group_extend_no_check(sb, o_blocks_count, add);
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if (err)
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goto out;
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--
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1.7.6.5
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