io_uring/rsrc: add reference count to struct io_mapped_ubuf

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>

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index d42114845fac6c46e8893156ba7f1ef3ad40e6b9..28f98de3c3042a25f88e5c824c86b4ebded938a7 100644 (file)
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -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;

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 3d0dda3556e6eae9f293e0516a583b57a93e62e3..98a253172c2739d4a71955d627b1f90ac0ffdbb2 100644 (file)
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -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);
 };