Op 08-11-2024 om 18:32 schreef David Howells:
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@xxxxxxxxxx>
cc: Jeff Layton <jlayton@xxxxxxxxxx>
cc: netfs@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
fs/netfs/Makefile | 1 +
fs/netfs/buffered_read.c | 119 ++++-------------
fs/netfs/direct_read.c | 14 +-
fs/netfs/direct_write.c | 10 +-
fs/netfs/internal.h | 4 -
fs/netfs/misc.c | 147 ---------------------
fs/netfs/objects.c | 2 +-
fs/netfs/read_pgpriv2.c | 32 ++---
fs/netfs/read_retry.c | 2 +-
fs/netfs/rolling_buffer.c | 225 +++++++++++++++++++++++++++++++++
fs/netfs/write_collect.c | 19 +--
fs/netfs/write_issue.c | 26 ++--
include/linux/netfs.h | 10 +-
include/linux/rolling_buffer.h | 61 +++++++++
include/trace/events/netfs.h | 2 +
15 files changed, 375 insertions(+), 299 deletions(-)
create mode 100644 fs/netfs/rolling_buffer.c
create mode 100644 include/linux/rolling_buffer.h
[...]
diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index 88f2adfab75e..0722fb9919a3 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -68,19 +68,19 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
* request.
*/
if (async || user_backed_iter(iter)) {
- n = netfs_extract_user_iter(iter, len, &wreq->iter, 0);
+ n = netfs_extract_user_iter(iter, len, &wreq->buffer.iter, 0);
if (n < 0) {
ret = n;
goto out;
}
- wreq->direct_bv = (struct bio_vec *)wreq->iter.bvec;
+ wreq->direct_bv = (struct bio_vec *)wreq->buffer.iter.bvec;
wreq->direct_bv_count = n;
wreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);
} else {
- wreq->iter = *iter;
+ wreq->buffer.iter = *iter;
}
- wreq->io_iter = wreq->iter;
+ wreq->buffer.iter = wreq->buffer.iter;
Is this correct, an assignment to itself?
}
__set_bit(NETFS_RREQ_USE_IO_ITER, &wreq->flags);
[...]
