Commit 6e6e2b86 authored by Long Li's avatar Long Li Committed by Steve French
Browse files

CIFS: Add support for direct I/O read 



With direct I/O read, we transfer the data directly from transport layer to
the user data buffer.

Change in v3: add support for kernel AIO

Change in v4:
Refactor common read code to __cifs_readv for direct and non-direct I/O.
Retry on direct I/O failure.

Signed-off-by: default avatarLong Li <longli@microsoft.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 0df444a0

fs/cifs/cifsfs.h

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ extern int cifs_open(struct inode *inode, struct file *file); 
extern int cifs_close(struct inode *inode, struct file *file);

extern int cifs_closedir(struct inode *inode, struct file *file);

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_strict_writev(struct kiocb *iocb, struct iov_iter *from);

fs/cifs/cifsglob.h

+5 −0
Original line number Diff line number Diff line
@@ -1186,6 +1186,11 @@ struct cifs_aio_ctx { 
	unsigned int		len;

	unsigned int		total_len;

	bool			should_dirty;

	/*

	 * Indicates if this aio_ctx is for direct_io,

	 * If yes, iter is a copy of the user passed iov_iter

	 */

	bool			direct_io;

};



struct cifs_readdata;

fs/cifs/file.c

+186 −39
Original line number Diff line number Diff line
@@ -2979,7 +2979,6 @@ cifs_uncached_readdata_release(struct kref *refcount) 
	kref_put(&rdata->ctx->refcount, cifs_aio_ctx_release);

	for (i = 0; i < rdata->nr_pages; i++) {

		put_page(rdata->pages[i]);

		rdata->pages[i] = NULL;

	}

	cifs_readdata_release(refcount);

}
@@ -3106,6 +3105,67 @@ cifs_uncached_copy_into_pages(struct TCP_Server_Info *server, 
	return uncached_fill_pages(server, rdata, iter, iter->count);

}



static int cifs_resend_rdata(struct cifs_readdata *rdata,

			struct list_head *rdata_list,

			struct cifs_aio_ctx *ctx)

{

	int wait_retry = 0;

	unsigned int rsize, credits;

	int rc;

	struct TCP_Server_Info *server =

		tlink_tcon(rdata->cfile->tlink)->ses->server;



	/*

	 * Try to resend this rdata, waiting for credits up to 3 seconds.

	 * Note: we are attempting to resend the whole rdata not in segments

	 */

	do {

		rc = server->ops->wait_mtu_credits(server, rdata->bytes,

						&rsize, &credits);



		if (rc)

			break;



		if (rsize < rdata->bytes) {

			add_credits_and_wake_if(server, credits, 0);

			msleep(1000);

			wait_retry++;

		}

	} while (rsize < rdata->bytes && wait_retry < 3);



	/*

	 * If we can't find enough credits to send this rdata

	 * release the rdata and return failure, this will pass

	 * whatever I/O amount we have finished to VFS.

	 */

	if (rsize < rdata->bytes) {

		rc = -EBUSY;

		goto out;

	}



	rc = -EAGAIN;

	while (rc == -EAGAIN) {

		rc = 0;

		if (rdata->cfile->invalidHandle)

			rc = cifs_reopen_file(rdata->cfile, true);

		if (!rc)

			rc = server->ops->async_readv(rdata);

	}



	if (!rc) {

		/* Add to aio pending list */

		list_add_tail(&rdata->list, rdata_list);

		return 0;

	}



	add_credits_and_wake_if(server, rdata->credits, 0);

out:

	kref_put(&rdata->refcount,

		cifs_uncached_readdata_release);



	return rc;

}



static int

cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,

		     struct cifs_sb_info *cifs_sb, struct list_head *rdata_list,
@@ -3117,6 +3177,9 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file, 
	int rc;

	pid_t pid;

	struct TCP_Server_Info *server;

	struct page **pagevec;

	size_t start;

	struct iov_iter direct_iov = ctx->iter;



	server = tlink_tcon(open_file->tlink)->ses->server;
@@ -3125,6 +3188,9 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file, 
	else

		pid = current->tgid;



	if (ctx->direct_io)

		iov_iter_advance(&direct_iov, offset - ctx->pos);



	do {

		rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,

						   &rsize, &credits);
@@ -3132,8 +3198,42 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file, 
			break;



		cur_len = min_t(const size_t, len, rsize);

		npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);



		if (ctx->direct_io) {



			cur_len = iov_iter_get_pages_alloc(

					&direct_iov, &pagevec,

					cur_len, &start);

			if (cur_len < 0) {

				cifs_dbg(VFS,

					"couldn't get user pages (cur_len=%zd)"

					" iter type %d"

					" iov_offset %zd count %zd\n",

					cur_len, direct_iov.type,

					direct_iov.iov_offset,

					direct_iov.count);

				dump_stack();

				break;

			}

			iov_iter_advance(&direct_iov, cur_len);



			rdata = cifs_readdata_direct_alloc(

					pagevec, cifs_uncached_readv_complete);

			if (!rdata) {

				add_credits_and_wake_if(server, credits, 0);

				rc = -ENOMEM;

				break;

			}



			npages = (cur_len + start + PAGE_SIZE-1) / PAGE_SIZE;

			rdata->page_offset = start;

			rdata->tailsz = npages > 1 ?

				cur_len-(PAGE_SIZE-start)-(npages-2)*PAGE_SIZE :

				cur_len;



		} else {



			npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);

			/* allocate a readdata struct */

			rdata = cifs_readdata_alloc(npages,

					    cifs_uncached_readv_complete);
@@ -3147,13 +3247,15 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file, 
			if (rc)

				goto error;



			rdata->tailsz = PAGE_SIZE;

		}



		rdata->cfile = cifsFileInfo_get(open_file);

		rdata->nr_pages = npages;

		rdata->offset = offset;

		rdata->bytes = cur_len;

		rdata->pid = pid;

		rdata->pagesz = PAGE_SIZE;

		rdata->tailsz = PAGE_SIZE;

		rdata->read_into_pages = cifs_uncached_read_into_pages;

		rdata->copy_into_pages = cifs_uncached_copy_into_pages;

		rdata->credits = credits;
@@ -3168,8 +3270,10 @@ error: 
			add_credits_and_wake_if(server, rdata->credits, 0);

			kref_put(&rdata->refcount,

				cifs_uncached_readdata_release);

			if (rc == -EAGAIN)

			if (rc == -EAGAIN) {

				iov_iter_revert(&direct_iov, cur_len);

				continue;

			}

			break;

		}
@@ -3225,6 +3329,8 @@ again: 
				 * reading.

				 */

				if (got_bytes && got_bytes < rdata->bytes) {

					rc = 0;

					if (!ctx->direct_io)

						rc = cifs_readdata_to_iov(rdata, to);

					if (rc) {

						kref_put(&rdata->refcount,
@@ -3233,30 +3339,44 @@ again: 
					}

				}



				if (ctx->direct_io) {

					/*

					 * Re-use rdata as this is a

					 * direct I/O

					 */

					rc = cifs_resend_rdata(

						rdata,

						&tmp_list, ctx);

				} else {

					rc = cifs_send_async_read(

						rdata->offset + got_bytes,

						rdata->bytes - got_bytes,

						rdata->cfile, cifs_sb,

						&tmp_list, ctx);



				list_splice(&tmp_list, &ctx->list);



					kref_put(&rdata->refcount,

						cifs_uncached_readdata_release);

				}



				list_splice(&tmp_list, &ctx->list);



				goto again;

			} else if (rdata->result)

				rc = rdata->result;

			else

			else if (!ctx->direct_io)

				rc = cifs_readdata_to_iov(rdata, to);



			/* if there was a short read -- discard anything left */

			if (rdata->got_bytes && rdata->got_bytes < rdata->bytes)

				rc = -ENODATA;



			ctx->total_len += rdata->got_bytes;

		}

		list_del_init(&rdata->list);

		kref_put(&rdata->refcount, cifs_uncached_readdata_release);

	}



	if (!ctx->direct_io) {

		for (i = 0; i < ctx->npages; i++) {

			if (ctx->should_dirty)

				set_page_dirty(ctx->bv[i].bv_page);
@@ -3264,6 +3384,7 @@ again: 
		}



		ctx->total_len = ctx->len - iov_iter_count(to);

	}



	cifs_stats_bytes_read(tcon, ctx->total_len);
@@ -3281,18 +3402,28 @@ again: 
		complete(&ctx->done);

}



ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)

static ssize_t __cifs_readv(

	struct kiocb *iocb, struct iov_iter *to, bool direct)

{

	struct file *file = iocb->ki_filp;

	ssize_t rc;

	size_t len;

	ssize_t total_read = 0;

	loff_t offset = iocb->ki_pos;

	struct file *file = iocb->ki_filp;

	struct cifs_sb_info *cifs_sb;

	struct cifs_tcon *tcon;

	struct cifsFileInfo *cfile;

	struct cifs_tcon *tcon;

	ssize_t rc, total_read = 0;

	loff_t offset = iocb->ki_pos;

	struct cifs_aio_ctx *ctx;



	/*

	 * iov_iter_get_pages_alloc() doesn't work with ITER_KVEC,

	 * fall back to data copy read path

	 * this could be improved by getting pages directly in ITER_KVEC

	 */

	if (direct && to->type & ITER_KVEC) {

		cifs_dbg(FYI, "use non-direct cifs_user_readv for kvec I/O\n");

		direct = false;

	}



	len = iov_iter_count(to);

	if (!len)

		return 0;
@@ -3319,13 +3450,19 @@ ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to) 
	if (iter_is_iovec(to))

		ctx->should_dirty = true;



	if (direct) {

		ctx->pos = offset;

		ctx->direct_io = true;

		ctx->iter = *to;

		ctx->len = len;

	} else {

		rc = setup_aio_ctx_iter(ctx, to, READ);

		if (rc) {

			kref_put(&ctx->refcount, cifs_aio_ctx_release);

			return rc;

		}



		len = ctx->len;

	}



	/* grab a lock here due to read response handlers can access ctx */

	mutex_lock(&ctx->aio_mutex);
@@ -3368,6 +3505,16 @@ ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to) 
	return rc;

}



ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to)

{

	return __cifs_readv(iocb, to, true);

}



ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to)

{

	return __cifs_readv(iocb, to, false);

}



ssize_t

cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)

{

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