On 09/12/2020 09:06, Christoph Hellwig wrote:
> On Wed, Dec 09, 2020 at 08:36:45AM +0000, Christoph Hellwig wrote:
>> This is making the iter type even more of a mess than it already is.
>> I think we at least need placeholders for 0/1 here and an explicit
>> flags namespace, preferably after the types.
>>
>> Then again I'd much prefer if we didn't even add the flag or at best
>> just add it for a short-term transition and move everyone over to the
>> new scheme. Otherwise the amount of different interfaces and supporting
>> code keeps exploding.
At least the flag can be ignored. Anyway sounds good to me. I'll take
your patch below to the series, thanks!
>
> Note that the only other callers that use iov_iter_bvec and asynchronous
> read/write are loop, target and nvme-target, so this should actually
> be pretty simple. Out of these only target needs something like this
> trivial change to keep the bvec available over the duration of the I/O,
> the other two should be fine already:
>
> ---
> From 581a8eabbb1759e3dcfee4b1d2e419f814a8cb80 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@xxxxxx>
> Date: Wed, 9 Dec 2020 10:05:04 +0100
> Subject: target/file: allocate the bvec array as part of struct target_core_file_cmd
>
> This saves one memory allocation, and ensures the bvecs aren't freed
> before the AIO completion. This will allow the lower level code to be
> optimized so that it can avoid allocating another bvec array.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/target/target_core_file.c | 20 ++++++--------------
> 1 file changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
> index 7143d03f0e027e..ed0c39a1f7c649 100644
> --- a/drivers/target/target_core_file.c
> +++ b/drivers/target/target_core_file.c
> @@ -241,6 +241,7 @@ struct target_core_file_cmd {
> unsigned long len;
> struct se_cmd *cmd;
> struct kiocb iocb;
> + struct bio_vec bvecs[];
> };
>
> static void cmd_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
> @@ -268,29 +269,22 @@ fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> struct target_core_file_cmd *aio_cmd;
> struct iov_iter iter = {};
> struct scatterlist *sg;
> - struct bio_vec *bvec;
> ssize_t len = 0;
> int ret = 0, i;
>
> - aio_cmd = kmalloc(sizeof(struct target_core_file_cmd), GFP_KERNEL);
> + aio_cmd = kmalloc(struct_size(aio_cmd, bvecs, sgl_nents), GFP_KERNEL);
> if (!aio_cmd)
> return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>
> - bvec = kcalloc(sgl_nents, sizeof(struct bio_vec), GFP_KERNEL);
> - if (!bvec) {
> - kfree(aio_cmd);
> - return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> - }
> -
> for_each_sg(sgl, sg, sgl_nents, i) {
> - bvec[i].bv_page = sg_page(sg);
> - bvec[i].bv_len = sg->length;
> - bvec[i].bv_offset = sg->offset;
> + aio_cmd->bvecs[i].bv_page = sg_page(sg);
> + aio_cmd->bvecs[i].bv_len = sg->length;
> + aio_cmd->bvecs[i].bv_offset = sg->offset;
>
> len += sg->length;
> }
>
> - iov_iter_bvec(&iter, is_write, bvec, sgl_nents, len);
> + iov_iter_bvec(&iter, is_write, aio_cmd->bvecs, sgl_nents, len);
>
> aio_cmd->cmd = cmd;
> aio_cmd->len = len;
> @@ -307,8 +301,6 @@ fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> else
> ret = call_read_iter(file, &aio_cmd->iocb, &iter);
>
> - kfree(bvec);
> -
> if (ret != -EIOCBQUEUED)
> cmd_rw_aio_complete(&aio_cmd->iocb, ret, 0);
>
>
--
Pavel Begunkov
