e2fsck: eliminate bad update link count attempt

Submitted by Tahsin Erdogan on July 17, 2017, 12:50 p.m.

Details

Message ID 20170717125035.12852-1-tahsin@google.com
State Accepted
Headers show

Commit Message

Tahsin Erdogan July 17, 2017, 12:50 p.m.
Extended attribute inodes have a link count of 1 but they are not
attached to any directories. When an xattr inode with zero ea
references is found, the remedy is to reconnect it to lost+found dir.
Since reconnect operation increments the link count, it would normally
become 2 but to avoid that, check_ea_inode() sets the link count to
zero in anticipation of reconnect operation. And it does it even when
e2fsck is invoked with -n option which causes a fatal e2fsck failure
as can be demonstrated with the following test script:

  mke2fs -b 4096 -I 256 -F -O extent,ea_inode /dev/sdb 1G
  mount /dev/sdb /mnt/sdb
  touch /mnt/sdb/x
  setfattr -n user.ie1 -v $(python -c "print 'v'*5000") /mnt/sdb/x
  umount /dev/sdb
  debugfs -w -R 'rm x' /dev/sdb
  e2fsck -f -n /dev/sdb

In this case, e2fsck fails with the following error:

  e2fsck 1.43.5-WIP (17-Feb-2017)
  Pass 1: Checking inodes, blocks, and sizes
  Pass 2: Checking directory structure
  Pass 3: Checking directory connectivity
  Pass 4: Checking reference counts
  ext2fs_write_inode: Attempt to write to filesystem opened read-only
  while writing inode 13 in check_ea_inode
  e2fsck: aborted

Setting link count to zero is not really required because e2fsck will
detect the discrepancy in link count and offer to fix it.

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
---
 e2fsck/pass4.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

Comments

Theodore Ts'o July 24, 2017, 4:11 a.m.
On Mon, Jul 17, 2017 at 05:50:35AM -0700, Tahsin Erdogan wrote:
> Extended attribute inodes have a link count of 1 but they are not
> attached to any directories. When an xattr inode with zero ea
> references is found, the remedy is to reconnect it to lost+found dir.
> Since reconnect operation increments the link count, it would normally
> become 2 but to avoid that, check_ea_inode() sets the link count to
> zero in anticipation of reconnect operation. And it does it even when
> e2fsck is invoked with -n option which causes a fatal e2fsck failure
> as can be demonstrated with the following test script:
> 
>   mke2fs -b 4096 -I 256 -F -O extent,ea_inode /dev/sdb 1G
>   mount /dev/sdb /mnt/sdb
>   touch /mnt/sdb/x
>   setfattr -n user.ie1 -v $(python -c "print 'v'*5000") /mnt/sdb/x
>   umount /dev/sdb
>   debugfs -w -R 'rm x' /dev/sdb
>   e2fsck -f -n /dev/sdb
> 
> In this case, e2fsck fails with the following error:
> 
>   e2fsck 1.43.5-WIP (17-Feb-2017)
>   Pass 1: Checking inodes, blocks, and sizes
>   Pass 2: Checking directory structure
>   Pass 3: Checking directory connectivity
>   Pass 4: Checking reference counts
>   ext2fs_write_inode: Attempt to write to filesystem opened read-only
>   while writing inode 13 in check_ea_inode
>   e2fsck: aborted
> 
> Setting link count to zero is not really required because e2fsck will
> detect the discrepancy in link count and offer to fix it.
> 
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>

Thanks, applied.

					- Ted

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diff --git a/e2fsck/pass4.c b/e2fsck/pass4.c
index 663f87ab59c0..b23347cdb6b0 100644
--- a/e2fsck/pass4.c
+++ b/e2fsck/pass4.c
@@ -122,17 +122,8 @@  static void check_ea_inode(e2fsck_t ctx, ext2_ino_t i,
 
 	if (ctx->ea_inode_refs)
 		ea_refcount_fetch(ctx->ea_inode_refs, i, &actual_refs);
-	if (!actual_refs) {
-		/*
-		 * There are no attribute references to the ea_inode.
-		 * Zero the link count so that when  inode is linked to
-		 * lost+found it has correct link count.
-		 */
-		inode->i_links_count = 0;
-		e2fsck_write_inode(ctx, i, EXT2_INODE(inode), "check_ea_inode");
-		ext2fs_icount_store(ctx->inode_link_info, i, 0);
+	if (!actual_refs)
 		return;
-	}
 
 	/*
 	 * There are some attribute references, link_counted is now considered