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, 160 insertions, 0 deletions

diff --git a/drivers/gpu/host1x/intr.c b/drivers/gpu/host1x/intr.c
new file mode 100644
index 000000000..6a383e0c6
--- /dev/null
+++ b/drivers/gpu/host1x/intr.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Tegra host1x Interrupt Management
+ *
+ * Copyright (c) 2010-2021, NVIDIA Corporation.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/overflow.h>
+#include "dev.h"
+#include "fence.h"
+#include "intr.h"
+
+static void host1x_intr_add_fence_to_list(struct host1x_fence_list *list,
+					  struct host1x_syncpt_fence *fence)
+{
+	struct host1x_syncpt_fence *fence_in_list;
+
+	list_for_each_entry_reverse(fence_in_list, &list->list, list) {
+		if ((s32)wrapping_sub(u32, fence_in_list->threshold, fence->threshold) <= 0) {
+			/* Fence in list is before us, we can insert here */
+			list_add(&fence->list, &fence_in_list->list);
+			return;
+		}
+	}
+
+	/* Add as first in list */
+	list_add(&fence->list, &list->list);
+}
+
+static void host1x_intr_update_hw_state(struct host1x *host, struct host1x_syncpt *sp)
+{
+	struct host1x_syncpt_fence *fence;
+
+	if (!list_empty(&sp->fences.list)) {
+		fence = list_first_entry(&sp->fences.list, struct host1x_syncpt_fence, list);
+
+		host1x_hw_intr_set_syncpt_threshold(host, sp->id, fence->threshold);
+		host1x_hw_intr_enable_syncpt_intr(host, sp->id);
+	} else {
+		host1x_hw_intr_disable_syncpt_intr(host, sp->id);
+	}
+}
+
+void host1x_intr_add_fence_locked(struct host1x *host, struct host1x_syncpt_fence *fence)
+{
+	struct host1x_fence_list *fence_list = &fence->sp->fences;
+
+	INIT_LIST_HEAD(&fence->list);
+
+	host1x_intr_add_fence_to_list(fence_list, fence);
+	host1x_intr_update_hw_state(host, fence->sp);
+}
+
+bool host1x_intr_remove_fence(struct host1x *host, struct host1x_syncpt_fence *fence)
+{
+	struct host1x_fence_list *fence_list = &fence->sp->fences;
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&fence_list->lock, irqflags);
+
+	if (list_empty(&fence->list)) {
+		spin_unlock_irqrestore(&fence_list->lock, irqflags);
+		return false;
+	}
+
+	list_del_init(&fence->list);
+	host1x_intr_update_hw_state(host, fence->sp);
+
+	spin_unlock_irqrestore(&fence_list->lock, irqflags);
+
+	return true;
+}
+
+void host1x_intr_handle_interrupt(struct host1x *host, unsigned int id)
+{
+	struct host1x_syncpt *sp = &host->syncpt[id];
+	struct host1x_syncpt_fence *fence, *tmp;
+	unsigned int value;
+
+	value = host1x_syncpt_load(sp);
+
+	spin_lock(&sp->fences.lock);
+
+	list_for_each_entry_safe(fence, tmp, &sp->fences.list, list) {
+		if ((wrapping_sub(u32, value, fence->threshold) & 0x80000000U) != 0U) {
+			/* Fence is not yet expired, we are done */
+			break;
+		}
+
+		list_del_init(&fence->list);
+		host1x_fence_signal(fence);
+	}
+
+	/*
+	 * Re-enable interrupt if necessary. The ISR already disabled the interrupt,
+	 * so if no fences remain, no update is needed.
+	 */
+	if (!list_empty(&sp->fences.list))
+		host1x_intr_update_hw_state(host, sp);
+
+	spin_unlock(&sp->fences.lock);
+}
+
+int host1x_intr_init(struct host1x *host)
+{
+	struct host1x_intr_irq_data *irq_data;
+	unsigned int id;
+	int i, err;
+
+	for (id = 0; id < host1x_syncpt_nb_pts(host); ++id) {
+		struct host1x_syncpt *syncpt = &host->syncpt[id];
+
+		spin_lock_init(&syncpt->fences.lock);
+		INIT_LIST_HEAD(&syncpt->fences.list);
+	}
+
+	irq_data = devm_kcalloc(host->dev, host->num_syncpt_irqs, sizeof(irq_data[0]), GFP_KERNEL);
+	if (!irq_data)
+		return -ENOMEM;
+
+	host1x_hw_intr_disable_all_syncpt_intrs(host);
+
+	for (i = 0; i < host->num_syncpt_irqs; i++) {
+		irq_data[i].host = host;
+		irq_data[i].offset = i;
+
+		err = devm_request_irq(host->dev, host->syncpt_irqs[i],
+				       host->intr_op->isr, IRQF_SHARED,
+				       "host1x_syncpt", &irq_data[i]);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+void host1x_intr_deinit(struct host1x *host)
+{
+}
+
+void host1x_intr_start(struct host1x *host)
+{
+	u32 hz = clk_get_rate(host->clk);
+	int err;
+
+	mutex_lock(&host->intr_mutex);
+	err = host1x_hw_intr_init_host_sync(host, DIV_ROUND_UP(hz, 1000000));
+	if (err) {
+		mutex_unlock(&host->intr_mutex);
+		return;
+	}
+	mutex_unlock(&host->intr_mutex);
+}
+
+void host1x_intr_stop(struct host1x *host)
+{
+	host1x_hw_intr_disable_all_syncpt_intrs(host);
+}