[v5,00/12] xfs: make buffer functions return error codes

Message

Darrick J. Wong Jan. 24, 2020, 5:18 a.m. UTC

Hi all,

Let's fix all the xfs read/get buffer functions to return the usual
integer error codes and pass the buffer pointer as a out-argument.  This
makes it so that we can return useful error output instead of making
callers infer ENOMEM or EAGAIN or whatever other reality they crave from
the NULL pointer that they get when things don't go perfectly.

FWIW, all XBF_TRYLOCK callers must now trigger retries if they receive
EAGAIN.  This may lead to a slight behavioral change in that TRYLOCK
callers will no longer retry for things like ENOMEM, though I didn't see
any obvious changes in user-visible behavior when running fstests.

After finishing the error code conversion, we straighten out the TRYLOCK
callers to remove all this null pointer checks in favor of explicit
EAGAIN checks; and then we change the buffer IO/corruption error
reporting so that we report whoever called the buffer code even when
reading a buffer in transaction context.

In v5 of this series I rearranged some of the patches so that the return
type conversions go from the lower levels of the buffer code upwards.
This eases some of the awkward warts of previous submissions.

This has been lightly tested with fstests.  Enjoy!
Comments and questions are, as always, welcome.

--D