[PATCH 4/6] xfs: xfs_trans_read_buf() should return an error on failure

[Alex Elder]

On Wed, 2011-03-23 at 17:14 +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> When inside a transaction and we fail to read a buffer,
> xfs_trans_read_buf returns a null buffer pointer and no error.
> xfs_do_da_buf() checks the error return, but not the buffer, and as
> a result this read failure condition causes a panic when it attempts
> to dereference the non-existant buffer.
> 
> Make xfs_trans_read_buf() return the same error for this situation
> regardless of whether it is in a transaction or not. This means
> every caller does not need to check both the error return and the
> buffer before proceeding to use the buffer.

Good idea.  Later we can clean up callers.  I see that not
all callers currently check for a null buffer return...

Reviewed-by: Alex Elder <aelder at sgi.com>

> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> ---
>  fs/xfs/xfs_trans_buf.c |    3 ++-