xfs: fix efi item leak on forced shutdown

After test 139, kmemleak shows:

unreferenced object 0xffff880078b405d8 (size 400):
  comm "xfs_io", pid 4904, jiffies 4294909383 (age 1186.728s)
  hex dump (first 32 bytes):
    60 c1 17 79 00 88 ff ff 60 c1 17 79 00 88 ff ff  `..y....`..y....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81afb04d>] kmemleak_alloc+0x2d/0x60
    [<ffffffff8115c6cf>] kmem_cache_alloc+0x13f/0x2b0
    [<ffffffff814aaa97>] kmem_zone_alloc+0x77/0xf0
    [<ffffffff814aab2e>] kmem_zone_zalloc+0x1e/0x50
    [<ffffffff8147cd6b>] xfs_efi_init+0x4b/0xb0
    [<ffffffff814a4ee8>] xfs_trans_get_efi+0x58/0x90
    [<ffffffff81455fab>] xfs_bmap_finish+0x8b/0x1d0
    [<ffffffff814851b4>] xfs_itruncate_finish+0x2c4/0x5d0
    [<ffffffff814a970f>] xfs_setattr+0x8df/0xa70
    [<ffffffff814b5c7b>] xfs_vn_setattr+0x1b/0x20
    [<ffffffff8117dc00>] notify_change+0x170/0x2e0
    [<ffffffff81163bf6>] do_truncate+0x66/0xa0
    [<ffffffff81163d0b>] sys_ftruncate+0xdb/0xe0
    [<ffffffff8103a002>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff

The cause of the leak is that the "remove" parameter of IOP_UNPIN()
is never set when a CIL push is aborted. This means that the EFI
item is never freed if it was in the push being cancelled. The
problem is specific to delayed logging, but has uncovered a couple
of problems with the handling of IOP_UNPIN(remove).

Firstly, we cannot safely call xfs_trans_del_item() from IOP_UNPIN()
in the CIL commit failure path or the iclog write failure path
because for delayed loging we have no transaction context. Hence we
must only call xfs_trans_del_item() if the log item being unpinned
has an active log item descriptor.

Secondly, xfs_trans_uncommit() does not handle log item descriptor
freeing during the traversal of log items on a transaction. It can
reference a freed log item descriptor when unpinning an EFI item.
Hence it needs to use a safe list traversal method to allow items to
be removed from the transaction during IOP_UNPIN().

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 98c6f73b6752..6f8c21ce0d6d 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -427,13 +427,15 @@ xfs_buf_item_unpin(
 
 		if (remove) {
 			/*
-			 * We have to remove the log item from the transaction
-			 * as we are about to release our reference to the
-			 * buffer.  If we don't, the unlock that occurs later
-			 * in xfs_trans_uncommit() will ry to reference the
+			 * If we are in a transaction context, we have to
+			 * remove the log item from the transaction as we are
+			 * about to release our reference to the buffer.  If we
+			 * don't, the unlock that occurs later in
+			 * xfs_trans_uncommit() will try to reference the
 			 * buffer which we no longer have a hold on.
 			 */
-			xfs_trans_del_item(lip);
+			if (lip->li_desc)
+				xfs_trans_del_item(lip);
 
 			/*
 			 * Since the transaction no longer refers to the buffer,