io_uring/memmap: implement mmap for regions

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The patch implements mmap for the param region and enables the kernel
allocation mode. Internally it uses a fixed mmap offset, however the
user has to use the offset returned in
struct io_uring_region_desc::mmap_offset.

Note, mmap doesn't and can't take ->uring_lock and the region / ring
lookup is protected by ->mmap_lock, and it's directly peeking at
ctx->param_region. We can't protect io_create_region() with the
mmap_lock as it'd deadlock, which is why io_create_region_mmap_safe()
initialises it for us in a temporary variable and then publishes it
with the lock taken. It's intentionally decoupled from main region
helpers, and in the future we might want to have a list of active
regions, which then could be protected by the ->mmap_lock.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/0f1212bd6af7fb39b63514b34fae8948014221d1.1732886067.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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This commit is contained in:

Pavel Begunkov 2024-11-29 13:34:32 +00:00 • committed by Jens Axboe

parent 1e21df691f

commit 087f997870

3 changed files with 67 additions and 10 deletions

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61

io_uring/memmap.c

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10

io_uring/memmap.h

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6

io_uring/register.c

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