tree db93c750daee944f024e6954659f8907100b48f9
parent 0fcb100d50835d6823723ef0898cd565b3796e0a
author Nathan Huckleberry <nhuck@google.com> 1658482702 +0000
committer Mike Snitzer <snitzer@kernel.org> 1659044774 -0400

dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag

Add an optional flag that ensures dm_bufio_client does not sleep
(primary focus is to service dm_bufio_get without sleeping). This
allows the dm-bufio cache to be queried from interrupt context.

To ensure that dm-bufio does not sleep, dm-bufio must use a spinlock
instead of a mutex. Additionally, to avoid deadlocks, special care
must be taken so that dm-bufio does not sleep while holding the
spinlock.

But again: the scope of this no_sleep is initially confined to
dm_bufio_get, so __alloc_buffer_wait_no_callback is _not_ changed to
avoid sleeping because __bufio_new avoids allocation for NF_GET.

Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>