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Message-ID: <CAKywueRa8Uw_wSk3DUMk_8b=56OPsDv5uOPwqiYVJU19amL3NQ@mail.gmail.com>
Date: Fri, 16 Nov 2018 16:20:44 -0800
From: Pavel Shilovsky <piastryyy@...il.com>
To: Long Li <longli@...rosoft.com>
Cc: Steve French <sfrench@...ba.org>,
linux-cifs <linux-cifs@...r.kernel.org>,
samba-technical <samba-technical@...ts.samba.org>,
Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Patch v4 2/3] CIFS: Add support for direct I/O write
ср, 31 окт. 2018 г. в 15:26, Long Li <longli@...uxonhyperv.com>:
>
> From: Long Li <longli@...rosoft.com>
>
> With direct I/O write, user supplied buffers are pinned to the memory and data
> are transferred directly from user buffers to the transport layer.
>
> Change in v3: add support for kernel AIO
>
> Change in v4:
> Refactor common write code to __cifs_writev for direct and non-direct I/O.
> Retry on direct I/O failure.
>
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
> fs/cifs/cifsfs.h | 1 +
> fs/cifs/file.c | 194 +++++++++++++++++++++++++++++++++++++++++++------------
> 2 files changed, 154 insertions(+), 41 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
> index 7fba9aa..e9c5103 100644
> --- a/fs/cifs/cifsfs.h
> +++ b/fs/cifs/cifsfs.h
> @@ -105,6 +105,7 @@ extern ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to);
> extern ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to);
> extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to);
> extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from);
> +extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from);
> extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from);
> extern int cifs_lock(struct file *, int, struct file_lock *);
> extern int cifs_fsync(struct file *, loff_t, loff_t, int);
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index daab878..1a41c04 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2524,6 +2524,55 @@ wdata_fill_from_iovec(struct cifs_writedata *wdata, struct iov_iter *from,
> }
>
> static int
> +cifs_resend_wdata(struct cifs_writedata *wdata, struct list_head *wdata_list, struct cifs_aio_ctx *ctx)
> +{
> + int wait_retry = 0;
> + unsigned int wsize, credits;
> + int rc;
> + struct TCP_Server_Info *server = tlink_tcon(wdata->cfile->tlink)->ses->server;
> +
> + /*
> + * Try to resend this wdata, waiting for credits up to 3 seconds.
> + * Note: we are attempting to resend the whole wdata not in segments
> + */
> + do {
> + rc = server->ops->wait_mtu_credits(server, wdata->bytes, &wsize, &credits);
> +
> + if (rc)
> + break;
> +
> + if (wsize < wdata->bytes) {
> + add_credits_and_wake_if(server, credits, 0);
> + msleep(1000);
> + wait_retry++;
> + }
> + } while (wsize < wdata->bytes && wait_retry < 3);
> +
> + if (wsize < wdata->bytes) {
> + rc = -EBUSY;
> + goto out;
> + }
> +
> + rc = -EAGAIN;
> + while (rc == -EAGAIN)
> + if (!wdata->cfile->invalidHandle ||
> + !(rc = cifs_reopen_file(wdata->cfile, false)))
> + rc = server->ops->async_writev(wdata,
> + cifs_uncached_writedata_release);
> +
> + if (!rc) {
> + list_add_tail(&wdata->list, wdata_list);
> + return 0;
> + }
> +
> + add_credits_and_wake_if(server, wdata->credits, 0);
> +out:
> + kref_put(&wdata->refcount, cifs_uncached_writedata_release);
> +
> + return rc;
> +}
> +
> +static int
> cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
> struct cifsFileInfo *open_file,
> struct cifs_sb_info *cifs_sb, struct list_head *wdata_list,
> @@ -2537,6 +2586,8 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
> loff_t saved_offset = offset;
> pid_t pid;
> struct TCP_Server_Info *server;
> + struct page **pagevec;
> + size_t start;
>
> if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
> pid = open_file->pid;
> @@ -2553,38 +2604,74 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
> if (rc)
> break;
>
> - nr_pages = get_numpages(wsize, len, &cur_len);
> - wdata = cifs_writedata_alloc(nr_pages,
> + if (ctx->direct_io) {
> + cur_len = iov_iter_get_pages_alloc(
> + from, &pagevec, wsize, &start);
> + if (cur_len < 0) {
> + cifs_dbg(VFS,
> + "direct_writev couldn't get user pages "
> + "(rc=%zd) iter type %d iov_offset %zd count"
> + " %zd\n",
> + cur_len, from->type,
> + from->iov_offset, from->count);
> + dump_stack();
> + break;
> + }
> + iov_iter_advance(from, cur_len);
> +
> + nr_pages = (cur_len + start + PAGE_SIZE - 1) / PAGE_SIZE;
> +
> + wdata = cifs_writedata_direct_alloc(pagevec,
> cifs_uncached_writev_complete);
> - if (!wdata) {
> - rc = -ENOMEM;
> - add_credits_and_wake_if(server, credits, 0);
> - break;
> - }
> + if (!wdata) {
> + rc = -ENOMEM;
> + add_credits_and_wake_if(server, credits, 0);
> + break;
> + }
>
> - rc = cifs_write_allocate_pages(wdata->pages, nr_pages);
> - if (rc) {
> - kfree(wdata);
> - add_credits_and_wake_if(server, credits, 0);
> - break;
> - }
>
> - num_pages = nr_pages;
> - rc = wdata_fill_from_iovec(wdata, from, &cur_len, &num_pages);
> - if (rc) {
> - for (i = 0; i < nr_pages; i++)
> - put_page(wdata->pages[i]);
> - kfree(wdata);
> - add_credits_and_wake_if(server, credits, 0);
> - break;
> - }
> + wdata->page_offset = start;
> + wdata->tailsz =
> + nr_pages > 1 ?
> + cur_len - (PAGE_SIZE - start) -
> + (nr_pages - 2) * PAGE_SIZE :
> + cur_len;
> + } else {
> + nr_pages = get_numpages(wsize, len, &cur_len);
> + wdata = cifs_writedata_alloc(nr_pages,
> + cifs_uncached_writev_complete);
> + if (!wdata) {
> + rc = -ENOMEM;
> + add_credits_and_wake_if(server, credits, 0);
> + break;
> + }
>
> - /*
> - * Bring nr_pages down to the number of pages we actually used,
> - * and free any pages that we didn't use.
> - */
> - for ( ; nr_pages > num_pages; nr_pages--)
> - put_page(wdata->pages[nr_pages - 1]);
> + rc = cifs_write_allocate_pages(wdata->pages, nr_pages);
> + if (rc) {
> + kfree(wdata);
> + add_credits_and_wake_if(server, credits, 0);
> + break;
> + }
> +
> + num_pages = nr_pages;
> + rc = wdata_fill_from_iovec(wdata, from, &cur_len, &num_pages);
> + if (rc) {
> + for (i = 0; i < nr_pages; i++)
> + put_page(wdata->pages[i]);
> + kfree(wdata);
> + add_credits_and_wake_if(server, credits, 0);
> + break;
> + }
> +
> + /*
> + * Bring nr_pages down to the number of pages we actually used,
> + * and free any pages that we didn't use.
> + */
> + for ( ; nr_pages > num_pages; nr_pages--)
> + put_page(wdata->pages[nr_pages - 1]);
> +
> + wdata->tailsz = cur_len - ((nr_pages - 1) * PAGE_SIZE);
> + }
>
> wdata->sync_mode = WB_SYNC_ALL;
> wdata->nr_pages = nr_pages;
> @@ -2593,7 +2680,6 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
> wdata->pid = pid;
> wdata->bytes = cur_len;
> wdata->pagesz = PAGE_SIZE;
> - wdata->tailsz = cur_len - ((nr_pages - 1) * PAGE_SIZE);
> wdata->credits = credits;
> wdata->ctx = ctx;
> kref_get(&ctx->refcount);
> @@ -2668,13 +2754,17 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
> INIT_LIST_HEAD(&tmp_list);
> list_del_init(&wdata->list);
>
> - iov_iter_advance(&tmp_from,
> + if (ctx->direct_io)
> + rc = cifs_resend_wdata(wdata, &tmp_list, ctx);
> + else {
> + iov_iter_advance(&tmp_from,
> wdata->offset - ctx->pos);
>
> - rc = cifs_write_from_iter(wdata->offset,
> + rc = cifs_write_from_iter(wdata->offset,
> wdata->bytes, &tmp_from,
> ctx->cfile, cifs_sb, &tmp_list,
> ctx);
> + }
>
> list_splice(&tmp_list, &ctx->list);
>
> @@ -2687,8 +2777,9 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
> kref_put(&wdata->refcount, cifs_uncached_writedata_release);
> }
>
> - for (i = 0; i < ctx->npages; i++)
> - put_page(ctx->bv[i].bv_page);
> + if (!ctx->direct_io)
> + for (i = 0; i < ctx->npages; i++)
> + put_page(ctx->bv[i].bv_page);
>
> cifs_stats_bytes_written(tcon, ctx->total_len);
> set_bit(CIFS_INO_INVALID_MAPPING, &CIFS_I(dentry->d_inode)->flags);
> @@ -2703,7 +2794,7 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
> complete(&ctx->done);
> }
>
> -ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> +static ssize_t __cifs_writev(struct kiocb *iocb, struct iov_iter *from, bool direct)
> {
> struct file *file = iocb->ki_filp;
> ssize_t total_written = 0;
> @@ -2712,13 +2803,18 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> struct cifs_sb_info *cifs_sb;
> struct cifs_aio_ctx *ctx;
> struct iov_iter saved_from = *from;
> + size_t len = iov_iter_count(from);
> int rc;
>
> /*
> - * BB - optimize the way when signing is disabled. We can drop this
> - * extra memory-to-memory copying and use iovec buffers for constructing
> - * write request.
> + * iov_iter_get_pages_alloc doesn't work with ITER_KVEC.
> + * In this case, fall back to non-direct write function.
> + * this could be improved by getting pages directly in ITER_KVEC
> */
> + if (direct && from->type & ITER_KVEC) {
> + cifs_dbg(FYI, "use non-direct cifs_writev for kvec I/O\n");
> + direct = false;
> + }
>
> rc = generic_write_checks(iocb, from);
> if (rc <= 0)
> @@ -2742,10 +2838,16 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
>
> ctx->pos = iocb->ki_pos;
>
> - rc = setup_aio_ctx_iter(ctx, from, WRITE);
> - if (rc) {
> - kref_put(&ctx->refcount, cifs_aio_ctx_release);
> - return rc;
> + if (direct) {
> + ctx->direct_io = true;
> + ctx->iter = *from;
> + ctx->len = len;
> + } else {
> + rc = setup_aio_ctx_iter(ctx, from, WRITE);
> + if (rc) {
> + kref_put(&ctx->refcount, cifs_aio_ctx_release);
> + return rc;
> + }
> }
>
> /* grab a lock here due to read response handlers can access ctx */
> @@ -2795,6 +2897,16 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> return total_written;
> }
>
> +ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from)
> +{
> + return __cifs_writev(iocb, from, true);
> +}
> +
> +ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> +{
> + return __cifs_writev(iocb, from, false);
> +}
> +
> static ssize_t
> cifs_writev(struct kiocb *iocb, struct iov_iter *from)
> {
> --
> 2.7.4
>
Did you measure the performance benefit of using O_DIRECT with your
patches for non-RDMA mode?
--
Best regards,
Pavel Shilovsky
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