linux-ext4 - Re: [PATCH] resize2fs: move bitmaps if shrinking would orphan them

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Message-ID: <20130621024707.GC10730@thunk.org>
Date:	Thu, 20 Jun 2013 22:47:07 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Leonardo Menezes Vaz <lvaz@...hat.com>
Subject: Re: [PATCH] resize2fs: move bitmaps if shrinking would orphan them

On Tue, Jun 18, 2013 at 08:37:05PM -0500, Eric Sandeen wrote:
> It is possible to have a flex_bg filesystem with block groups
> which have inode & block bitmaps at some point well past the
> start of the group.
> 
> If an offline shrink puts the new size somewhere between
> the start of the block group and the (old) location of
> the bitmaps, they can be left beyond the end of the filesystem,
> i.e. result in fs corruption.
> 
> Check each remaining block group for whether its bitmaps
> are beyond the end of the new filesystem, and reallocate
> them in a new location if needed.
> 
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>

Looks good, thanks for the patch.  I made a few minor changes to fix
up some extra whitespace and a minor optimization.

   	      		       	     - Ted

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 28131c2..204b10a 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -889,7 +889,7 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
 	 * bitmaps which are beyond the end of the new filesystem.
 	 */
 	new_size = ext2fs_blocks_count(fs->super);
-	if (ext2fs_blocks_count(fs->super) < ext2fs_blocks_count(old_fs->super)) {
+	if (new_size < ext2fs_blocks_count(old_fs->super)) {
 		for (g = 0; g < fs->group_desc_count; g++) {
 			/*
 			 * ext2fs_allocate_group_table re-allocates bitmaps
@@ -900,13 +900,13 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
 				retval = ext2fs_allocate_group_table(fs, g, 0);
 				if (retval)
 					return retval;
-			} 
+			}
 			if (ext2fs_inode_bitmap_loc(fs, g) >= new_size) {
 				ext2fs_inode_bitmap_loc_set(fs, g, 0);
 				retval = ext2fs_allocate_group_table(fs, g, 0);
 				if (retval)
 					return retval;
-			} 
+			}
 		}
 	}
 
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