[PATCH 05/26] netfs: Fix read abandonment during retry

[Paulo Alcantara]

David Howells <dhowells at redhat.com> writes:

> Under certain circumstances, all the remaining subrequests from a read
> request will get abandoned during retry.  The abandonment process expects
> the 'subreq' variable to be set to the place to start abandonment from, but
> it doesn't always have a useful value (it will be uninitialised on the
> first pass through the loop and it may point to a deleted subrequest on
> later passes).
>
> Fix the first jump to "abandon:" to set subreq to the start of the first
> subrequest expected to need retry (which, in this abandonment case, turned
> out unexpectedly to no longer have NEED_RETRY set).
>
> Also clear the subreq pointer after discarding superfluous retryable
> subrequests to cause an oops if we do try to access it.
>
> Signed-off-by: David Howells <dhowells at redhat.com>
> cc: Paulo Alcantara <pc at manguebit.org>
> cc: netfs at lists.linux.dev
> cc: linux-fsdevel at vger.kernel.org
> Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
> ---
>  fs/netfs/read_retry.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Reviewed-by: Paulo Alcantara (Red Hat) <pc at manguebit.org>