This is an attempt to revive discussion after bringing it up as a reply to the last attempt last week. Since the problem with the previous attempt at adding getdents to io_uring was that offset was problematic, we can just not add an offset parameter: using different offsets is rarely useful in practice (maybe for some cacheless userspace NFS server?) and more isn't worth the cost of allowing arbitrary offsets: just allow rewind as a flag instead. [happy to drop even that flag for what I care about, but that might be useful enough on its own as io_uring rightfully has no seek API] The new API does nothing that cannot be achieved with plain syscalls so it shouldn't be introducing any new problem, the only downside is that having the state in the file struct isn't very uring-ish and if a better solution is found later that will probably require duplicating some logic in a new flag... But that seems like it would likely be a distant future, and this version should be usable right away. To repeat the rationale for having getdents available from uring as it has been a while, while I believe there can be real performance improvements as suggested in [1], the real reason is to allow coherency in code: applications using io_uring usually center their event loop around the ring, and having the occasional synchronous getdents call in there is cumbersome and hard to do properly when you consider e.g. a slow or acting up network fs... [1] https://lore.kernel.org/linux-fsdevel/20210218122640.GA334506@xxxxxxxxxxxxxx/ (unfortunately the source is no longer available...) liburing implementation: https://github.com/martinetd/liburing/commits/getdents (will submit properly after initial discussions here) Previous discussion: https://lore.kernel.org/all/20211221164004.119663-1-shr@xxxxxx/T/#m517583f23502f32b040c819d930359313b3db00c Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx> --- Dominique Martinet (2): fs: split off vfs_getdents function of getdents64 syscall io_uring: add support for getdents fs/internal.h | 8 +++++++ fs/readdir.c | 33 +++++++++++++++++++++------- include/uapi/linux/io_uring.h | 7 ++++++ io_uring/fs.c | 51 +++++++++++++++++++++++++++++++++++++++++++ io_uring/fs.h | 3 +++ io_uring/opdef.c | 8 +++++++ 6 files changed, 102 insertions(+), 8 deletions(-) --- base-commit: 6a8f57ae2eb07ab39a6f0ccad60c760743051026 change-id: 20230422-uring-getdents-2aab84d240aa Best regards, -- Dominique Martinet | Asmadeus
