netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 159 insertions, 0 deletions

diff --git a/drivers/interconnect/bulk.c b/drivers/interconnect/bulk.c
new file mode 100644
index 000000000..8b1d8a412
--- /dev/null
+++ b/drivers/interconnect/bulk.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/interconnect-provider.h>
+#include <linux/device.h>
+#include <linux/export.h>
+
+/**
+ * of_icc_bulk_get() - get interconnect paths
+ * @dev: the device requesting the path
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the table with the paths we want to get
+ *
+ * Returns 0 on success or negative errno otherwise.
+ */
+int __must_check of_icc_bulk_get(struct device *dev, int num_paths,
+				 struct icc_bulk_data *paths)
+{
+	int ret, i;
+
+	for (i = 0; i < num_paths; i++) {
+		paths[i].path = of_icc_get(dev, paths[i].name);
+		if (IS_ERR(paths[i].path)) {
+			ret = PTR_ERR(paths[i].path);
+			if (ret != -EPROBE_DEFER)
+				dev_err(dev, "of_icc_get() failed on path %s (%d)\n",
+					paths[i].name, ret);
+			paths[i].path = NULL;
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	icc_bulk_put(i, paths);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_icc_bulk_get);
+
+/**
+ * icc_bulk_put() - put a list of interconnect paths
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the icc_bulk_data table with the paths being put
+ */
+void icc_bulk_put(int num_paths, struct icc_bulk_data *paths)
+{
+	while (--num_paths >= 0) {
+		icc_put(paths[num_paths].path);
+		paths[num_paths].path = NULL;
+	}
+}
+EXPORT_SYMBOL_GPL(icc_bulk_put);
+
+/**
+ * icc_bulk_set_bw() - set bandwidth to a set of paths
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the icc_bulk_data table containing the paths and bandwidth
+ *
+ * Returns 0 on success or negative errno otherwise.
+ */
+int icc_bulk_set_bw(int num_paths, const struct icc_bulk_data *paths)
+{
+	int ret = 0;
+	int i;
+
+	for (i = 0; i < num_paths; i++) {
+		ret = icc_set_bw(paths[i].path, paths[i].avg_bw, paths[i].peak_bw);
+		if (ret) {
+			pr_err("icc_set_bw() failed on path %s (%d)\n", paths[i].name, ret);
+			return ret;
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(icc_bulk_set_bw);
+
+/**
+ * icc_bulk_enable() - enable a previously disabled set of paths
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the icc_bulk_data table containing the paths and bandwidth
+ *
+ * Returns 0 on success or negative errno otherwise.
+ */
+int icc_bulk_enable(int num_paths, const struct icc_bulk_data *paths)
+{
+	int ret, i;
+
+	for (i = 0; i < num_paths; i++) {
+		ret = icc_enable(paths[i].path);
+		if (ret) {
+			pr_err("icc_enable() failed on path %s (%d)\n", paths[i].name, ret);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	icc_bulk_disable(i, paths);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(icc_bulk_enable);
+
+/**
+ * icc_bulk_disable() - disable a set of interconnect paths
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the icc_bulk_data table containing the paths and bandwidth
+ */
+void icc_bulk_disable(int num_paths, const struct icc_bulk_data *paths)
+{
+	while (--num_paths >= 0)
+		icc_disable(paths[num_paths].path);
+}
+EXPORT_SYMBOL_GPL(icc_bulk_disable);
+
+struct icc_bulk_devres {
+	struct icc_bulk_data *paths;
+	int num_paths;
+};
+
+static void devm_icc_bulk_release(struct device *dev, void *res)
+{
+	struct icc_bulk_devres *devres = res;
+
+	icc_bulk_put(devres->num_paths, devres->paths);
+}
+
+/**
+ * devm_of_icc_bulk_get() - resource managed of_icc_bulk_get
+ * @dev: the device requesting the path
+ * @num_paths: the number of icc_bulk_data
+ * @paths: the table with the paths we want to get
+ *
+ * Returns 0 on success or negative errno otherwise.
+ */
+int devm_of_icc_bulk_get(struct device *dev, int num_paths, struct icc_bulk_data *paths)
+{
+	struct icc_bulk_devres *devres;
+	int ret;
+
+	devres = devres_alloc(devm_icc_bulk_release, sizeof(*devres), GFP_KERNEL);
+	if (!devres)
+		return -ENOMEM;
+
+	ret = of_icc_bulk_get(dev, num_paths, paths);
+	if (!ret) {
+		devres->paths = paths;
+		devres->num_paths = num_paths;
+		devres_add(dev, devres);
+	} else {
+		devres_free(devres);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_of_icc_bulk_get);