This patch tries to avoid EAGAIN due to nrpages!=0 that was originally trying to drop stale pages resulting in wrong data access. Report: https://bugs.chromium.org/p/chromium/issues/detail?id=938958#c38

Cc: stable@vger.kernel.org Cc: Jens Axboe axboe@kernel.dk Cc: linux-block@vger.kernel.org Cc: Bart Van Assche bvanassche@acm.org Fixes: 5db470e229e2 ("loop: drop caches if offset or block_size are changed") Reported-by: Gwendal Grignou gwendal@chromium.org Reported-by: grygorii tertychnyi gtertych@cisco.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org

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v2 from v1:

• remove obsolete jump

FWIW, after applying this patch to 4.19.47, losetup is not failing any more for me.

Thanks, Francesco Ruggeri