linux-toradex.git/include/linux/rolling_buffer.h, branch v6.16-rc6 Linux kernel for Apalis and Colibri modules netfs: Abstract out a rolling folio buffer implementation 2024-12-20T21:34:02+00:00 David Howells dhowells@redhat.com 2024-12-16T20:40:55+00:00 06fa229ceb36898e68022b5654c017d2c6582d7d A rolling buffer is a series of folios held in a list of folio_queues. New folios and folio_queue structs may be inserted at the head simultaneously with spent ones being removed from the tail without the need for locking. The rolling buffer includes an iov_iter and it has to be careful managing this as the list of folio_queues is extended such that an oops doesn't incurred because the iterator was pointing to the end of a folio_queue segment that got appended to and then removed. We need to use the mechanism twice, once for read and once for write, and, in future patches, we will use a second rolling buffer to handle bounce buffering for content encryption. Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20241216204124.3752367-6-dhowells@redhat.com cc: Jeff Layton <jlayton@kernel.org> cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> 
A rolling buffer is a series of folios held in a list of folio_queues.  New
folios and folio_queue structs may be inserted at the head simultaneously
with spent ones being removed from the tail without the need for locking.

The rolling buffer includes an iov_iter and it has to be careful managing
this as the list of folio_queues is extended such that an oops doesn't
incurred because the iterator was pointing to the end of a folio_queue
segment that got appended to and then removed.

We need to use the mechanism twice, once for read and once for write, and,
in future patches, we will use a second rolling buffer to handle bounce
buffering for content encryption.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241216204124.3752367-6-dhowells@redhat.com
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>