kernel/linux.git/io_uring/kbuf.h, branch v7.1-rc5

io_uring/kbuf: support min length left for incremental buffers

2026-04-28T22:08:56+00:00

Incrementally consumed buffer rings are generally fully consumed, but it's quite possible that the application has a minimum size it needs to meet to avoid truncation. Currently that minimum limit is 1 byte, but this should be a setting that is the hands of the application. For recvmsg multishot, a prime use case for incrementally consumed buffers, the application may get spurious -EFAULT returned at the end of an incrementally consumed buffer, as less space is available than the headers need. Grab a u32 field in struct io_uring_buf_reg, which the application can use to inform the kernel of the minimum size that should be available in an incrementally consumed buffer. If less than that is available, the current buffer is fully processed and the next one will be picked. Cc: stable@vger.kernel.org Fixes: ae98dbf43d75 ("io_uring/kbuf: add support for incremental buffer consumption") Link: https://github.com/axboe/liburing/issues/1433 Signed-off-by: Martin Michaelis [axboe: write commit message, change io_buffer_list member name] Reviewed-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe

io_uring/kbuf: kill dead struct io_buffer_list 'nr_entries' member

2026-04-28T22:08:44+00:00

This is only ever assigned, never used. The only used part is the calculated mask, which is used for indexing. Kill 'nr_entries'. Reviewed-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe

io_uring/kbuf: remove obsolete buf_nr_pages and update comments

2025-11-20T20:23:05+00:00

The buf_nr_pages field in io_buffer_list was previously used to determine whether the buffer list uses ring-provided buffers or classic provided buffers. This is now determined by checking the IOBL_BUF_RING flag. Remove the buf_nr_pages field and update related comments. Signed-off-by: Joanne Koong Signed-off-by: Jens Axboe

io-uring: move `struct io_br_sel` into io_uring_types.h

2025-08-24T17:41:12+00:00

Move `struct io_br_sel` into io_uring_types.h and prepare for supporting provided buffer on uring_cmd. Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20250821040210.1152145-2-ming.lei@redhat.com Signed-off-by: Jens Axboe

io_uring/kbuf: check for ring provided buffers first in recycling

2025-08-24T17:41:12+00:00

This is the most likely of paths if a provided buffer is used, so offer it up first and push the legacy buffers to later. Link: https://lore.kernel.org/r/20250821020750.598432-14-axboe@kernel.dk Signed-off-by: Jens Axboe

io_uring/kbuf: switch to storing struct io_buffer_list locally

2025-08-24T17:41:12+00:00

Currently the buffer list is stored in struct io_kiocb. The buffer list can be of two types: 1) Classic/legacy buffer list. These don't need to get referenced after a buffer pick, and hence storing them in struct io_kiocb is perfectly fine. 2) Ring provided buffer lists. These DO need to be referenced after the initial buffer pick, as they need to get consumed later on. This can be either just incrementing the head of the ring, or it can be consuming parts of a buffer if incremental buffer consumptions has been configured. For case 2, io_uring needs to be careful not to access the buffer list after the initial pick-and-execute context. The core does recycling of these, but it's easy to make a mistake, because it's stored in the io_kiocb which does persist across multiple execution contexts. Either because it's a multishot request, or simply because it needed some kind of async trigger (eg poll) for retry purposes. Add a struct io_buffer_list to struct io_br_sel, which is always on stack for the various users of it. This prevents the buffer list from leaking outside of that execution context, and additionally it enables kbuf to not even pass back the struct io_buffer_list if the given context isn't appropriately locked already. This doesn't fix any bugs, it's simply a defensive measure to prevent any issues with reuse of a buffer list. Link: https://lore.kernel.org/r/20250821020750.598432-12-axboe@kernel.dk Signed-off-by: Jens Axboe

io_uring/kbuf: use struct io_br_sel for multiple buffers picking

2025-08-24T17:41:12+00:00

The networking side uses bundles, which is picking multiple buffers at the same time. Pass in struct io_br_sel to those helpers. Link: https://lore.kernel.org/r/20250821020750.598432-9-axboe@kernel.dk Signed-off-by: Jens Axboe

io_uring/kbuf: introduce struct io_br_sel

2025-08-24T17:41:12+00:00

Rather than return addresses directly from buffer selection, add a struct around it. No functional changes in this patch, it's in preparation for storing more buffer related information locally, rather than in struct io_kiocb. Link: https://lore.kernel.org/r/20250821020750.598432-7-axboe@kernel.dk Signed-off-by: Jens Axboe

io_uring/kbuf: pass in struct io_buffer_list to commit/recycle helpers

2025-08-24T17:41:12+00:00

Rather than have this implied being in the io_kiocb, pass it in directly so it's immediately obvious where these users of ->buf_list are coming from. Link: https://lore.kernel.org/r/20250821020750.598432-6-axboe@kernel.dk Signed-off-by: Jens Axboe

io_uring/kbuf: drop 'issue_flags' from io_put_kbuf(s)() arguments

2025-08-24T17:41:11+00:00

Picking multiple buffers always requires the ring lock to be held across the operation, so there's no need to pass in the issue_flags to io_put_kbufs(). On the single buffer side, if the initial picking of a ring buffer was unlocked, then it will have been committed already. For legacy buffers, no locking is required, as they will simply be freed. Link: https://lore.kernel.org/r/20250821020750.598432-3-axboe@kernel.dk Signed-off-by: Jens Axboe