xfs: fix a double completion for buffers on in-memory targets

__xfs_buf_submit calls xfs_buf_ioend when b_io_remaining hits zero.  For
in-memory buftargs b_io_remaining is never incremented from it's initial
value of 1, so this always happens.  Thus the extra call to xfs_buf_ioend
in _xfs_buf_ioapply causes a double completion.  Fortunately
__xfs_buf_submit is only used for synchronous reads on in-memory buftargs
due to the peculiarities of how they work, so this is mostly harmless and
just causes a little extra work to be done.

Fixes: 5076a60 ("xfs: support in-memory buffer cache targets")
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Acked-by: Dave Chinner <[email protected]>
Signed-off-by: Carlos Maiolino <[email protected]>

Author: Christoph Hellwig

fs/xfs/xfs_buf.c

@@ -1657,10 +1657,8 @@ _xfs_buf_ioapply(
 	op |= REQ_META;
 
 	/* in-memory targets are directly mapped, no IO required. */
-	if (xfs_buftarg_is_mem(bp->b_target)) {
-		xfs_buf_ioend(bp);
+	if (xfs_buftarg_is_mem(bp->b_target))
 		return;
-	}
 
 	/*
 	 * Walk all the vectors issuing IO on them. Set up the initial offset