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, 102 insertions, 0 deletions

diff --git a/drivers/accessibility/speakup/utils.h b/drivers/accessibility/speakup/utils.h
new file mode 100644
index 000000000..db00c962f
--- /dev/null
+++ b/drivers/accessibility/speakup/utils.h
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* utils.h
+ * originally written by: Kirk Reiser.
+ *
+ ** Copyright (C) 2002  Kirk Reiser.
+ *  Copyright (C) 2003  David Borowski.
+ */
+
+#include <stdio.h>
+
+#define MAXKEYS 512
+#define MAXKEYVAL 160
+#define HASHSIZE 101
+#define is_shift -3
+#define is_spk -2
+#define is_input -1
+
+struct st_key {
+	char *name;
+	struct st_key *next;
+	int value, shift;
+};
+
+struct st_key key_table[MAXKEYS];
+struct st_key *extra_keys = key_table+HASHSIZE;
+char *def_name, *def_val;
+FILE *infile;
+int lc;
+
+char filename[256];
+
+static inline void open_input(const char *dir_name, const char *name)
+{
+	if (dir_name)
+		snprintf(filename, sizeof(filename), "%s/%s", dir_name, name);
+	else
+		snprintf(filename, sizeof(filename), "%s", name);
+	infile = fopen(filename, "r");
+	if (!infile) {
+		fprintf(stderr, "can't open %s\n", filename);
+		exit(1);
+	}
+	lc = 0;
+}
+
+static inline int oops(const char *msg, const char *info)
+{
+	if (info == NULL)
+		info = "";
+	fprintf(stderr, "error: file %s line %d\n", filename, lc);
+	fprintf(stderr, "%s %s\n", msg, info);
+	exit(1);
+}
+
+static inline struct st_key *hash_name(char *name)
+{
+	unsigned char *pn = (unsigned char *)name;
+	int hash = 0;
+
+	while (*pn) {
+		hash = (hash * 17) & 0xfffffff;
+		if (isupper(*pn))
+			*pn = tolower(*pn);
+		hash += (int)*pn;
+		pn++;
+	}
+	hash %= HASHSIZE;
+	return &key_table[hash];
+}
+
+static inline struct st_key *find_key(char *name)
+{
+	struct st_key *this = hash_name(name);
+
+	while (this) {
+		if (this->name && !strcmp(name, this->name))
+			return this;
+		this = this->next;
+	}
+	return this;
+}
+
+static inline struct st_key *add_key(char *name, int value, int shift)
+{
+	struct st_key *this = hash_name(name);
+
+	if (extra_keys-key_table >= MAXKEYS)
+		oops("out of key table space, enlarge MAXKEYS", NULL);
+	if (this->name != NULL) {
+		while (this->next) {
+			if (!strcmp(name, this->name))
+				oops("attempt to add duplicate key", name);
+			this = this->next;
+		}
+		this->next = extra_keys++;
+		this = this->next;
+	}
+	this->name = strdup(name);
+	this->value = value;
+	this->shift = shift;
+	return this;
+}