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Message-ID: <CAKywueTc7AHR-NEJu9dgWv9m_2A-MkOpsdQGZSt+X3u9kyX54Q@mail.gmail.com>
Date: Fri, 21 Sep 2018 15:30:18 -0700
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>,
linux-rdma@...r.kernel.org
Subject: Re: [PATCH V3 (resend) 4/7] CIFS: Add support for direct I/O write
чт, 20 сент. 2018 г. в 14:22, 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
>
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
> fs/cifs/cifsfs.h | 1 +
> fs/cifs/file.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++---------
> 2 files changed, 166 insertions(+), 31 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
> index ed5479c..cc54051 100644
> --- a/fs/cifs/cifsfs.h
> +++ b/fs/cifs/cifsfs.h
> @@ -104,6 +104,7 @@ 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 6a939fa..2a5d209 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2537,6 +2537,8 @@ 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 +2555,74 @@ 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 +2631,6 @@ 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);
> @@ -2687,8 +2724,9 @@ 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);
> @@ -2703,6 +2741,102 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
> complete(&ctx->done);
> }
>
> +ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from)
the same comment as for readv: this function is almost identical to
cifs_user_writev, can't the latter be refactored to avoid code
duplication?
> +{
> + struct file *file = iocb->ki_filp;
> + ssize_t total_written = 0;
> + struct cifsFileInfo *cfile;
> + struct cifs_tcon *tcon;
> + struct cifs_sb_info *cifs_sb;
> + struct TCP_Server_Info *server;
> + size_t len = iov_iter_count(from);
> + int rc;
> + struct cifs_aio_ctx *ctx;
> +
> + /*
> + * 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 (from->type & ITER_KVEC) {
> + cifs_dbg(FYI, "use non-direct cifs_user_writev for kvec I/O\n");
> + return cifs_user_writev(iocb, from);
> + }
> +
> + rc = generic_write_checks(iocb, from);
> + if (rc <= 0)
> + return rc;
> +
> + cifs_sb = CIFS_FILE_SB(file);
> + cfile = file->private_data;
> + tcon = tlink_tcon(cfile->tlink);
> + server = tcon->ses->server;
> +
> + if (!server->ops->async_writev)
> + return -ENOSYS;
> +
> + ctx = cifs_aio_ctx_alloc();
> + if (!ctx)
> + return -ENOMEM;
> +
> + ctx->cfile = cifsFileInfo_get(cfile);
> +
> + if (!is_sync_kiocb(iocb))
> + ctx->iocb = iocb;
> +
> + ctx->pos = iocb->ki_pos;
> +
> + ctx->direct_io = true;
> + ctx->iter = *from;
> + ctx->len = len;
> +
> + /* grab a lock here due to read response handlers can access ctx */
> + mutex_lock(&ctx->aio_mutex);
> +
> + rc = cifs_write_from_iter(iocb->ki_pos, ctx->len, from,
> + cfile, cifs_sb, &ctx->list, ctx);
> +
> + /*
> + * If at least one write was successfully sent, then discard any rc
> + * value from the later writes. If the other write succeeds, then
> + * we'll end up returning whatever was written. If it fails, then
> + * we'll get a new rc value from that.
> + */
> + if (!list_empty(&ctx->list))
> + rc = 0;
> +
> + mutex_unlock(&ctx->aio_mutex);
> +
> + if (rc) {
> + kref_put(&ctx->refcount, cifs_aio_ctx_release);
> + return rc;
> + }
> +
> + if (!is_sync_kiocb(iocb)) {
> + kref_put(&ctx->refcount, cifs_aio_ctx_release);
> + return -EIOCBQUEUED;
> + }
> +
> + rc = wait_for_completion_killable(&ctx->done);
> + if (rc) {
> + mutex_lock(&ctx->aio_mutex);
> + ctx->rc = rc = -EINTR;
> + total_written = ctx->total_len;
> + mutex_unlock(&ctx->aio_mutex);
> + } else {
> + rc = ctx->rc;
> + total_written = ctx->total_len;
> + }
> +
> + kref_put(&ctx->refcount, cifs_aio_ctx_release);
> +
> + if (unlikely(!total_written))
> + return rc;
> +
> + iocb->ki_pos += total_written;
> + return total_written;
> +}
> +
> ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> {
> struct file *file = iocb->ki_filp;
> --
> 2.7.4
>
--
Best regards,
Pavel Shilovsky
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