io_uring_buf_ring_available(3) — Linux manual page


io_uring_b...g_available(3)  liburing Manual io_uring_b...g_available(3)

NAME         top

       io_uring_buf_ring_available - return number of unconsumed
       provided ring buffer entries

SYNOPSIS         top

       #include <liburing.h>

       int io_uring_buf_ring_available(struct io_uring *ring,
                                       struct io_uring_buf_ring *br,
                                       unsigned short bgid);

DESCRIPTION         top

       The io_uring_buf_ring_available(3) helper returns the number of
       unconsumed (by the kernel) entries in the br provided buffer
       group belonging to the io_uring ring and identified by the buffer
       group ID bgid.

       Since the head of the provided buffer ring is only visible to the
       kernel, it's impossible to otherwise know how many unconsumed
       entries exist in the given provided buffer ring. This function
       query the kernel to return that number.

NOTES         top

       The returned number of entries reflect the amount of unconsumed
       entries at the time that it was queried. If inflight IO exists
       that may consume provided buffers from this buffer group, then
       the returned value is inherently racy.

RETURN VALUE         top

       Returns the number of unconsumed entries on success, which may be
       0. In case of error, may return -ENOENT if the specified buffer
       group doesn't exist, or -EINVAL if the buffer group isn't of the
       correct type, or if the kernel doesn't support this feature.

SEE ALSO         top

       io_uring_register_buf_ring(3), io_uring_buf_ring_add(3),

COLOPHON         top

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liburing-2.6                  Jan 11, 2024   io_uring_b...g_available(3)

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