unimore/kernel-hacking-2024-linux-steffo
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io_uring/rsrc: add reference count to struct io_mapped_ubuf

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Currently there's a single ring owner of a mapped buffer, and hence the
reference count will always be 1 when it's torn down and freed. However,
in preparation for being able to link io_mapped_ubuf to different spots,
add a reference count to manage the lifetime of it.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2024-09-11 13:54:32 -06:00
parent 021b153f7d
commit bfc0aa7a51
2 changed files with 4 additions and 0 deletions
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3
io_uring/rsrc.c
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@ -116,6 +116,8 @@ static void io_buffer_unmap(struct io_ring_ctx *ctx, struct io_mapped_ubuf **slo
*slot = NULL;
if (imu != &dummy_ubuf) {
if (!refcount_dec_and_test(&imu->refs))
return;
for (i = 0; i < imu->nr_bvecs; i++)
unpin_user_page(imu->bvec[i].bv_page);
if (imu->acct_pages)
@ -990,6 +992,7 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
imu->folio_shift = data.folio_shift;
imu->folio_mask = ~((1UL << data.folio_shift) - 1);
}
refcount_set(&imu->refs, 1);
off = (unsigned long) iov->iov_base & ~imu->folio_mask;
*pimu = imu;
ret = 0;

1
io_uring/rsrc.h
View file

@ -47,6 +47,7 @@ struct io_mapped_ubuf {
unsigned int folio_shift;
unsigned long acct_pages;
unsigned long folio_mask;
refcount_t refs;
struct bio_vec bvec[] __counted_by(nr_bvecs);
};