From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read 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 Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- drivers/firmware/google/memconsole.c | 54 ++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 drivers/firmware/google/memconsole.c (limited to 'drivers/firmware/google/memconsole.c') diff --git a/drivers/firmware/google/memconsole.c b/drivers/firmware/google/memconsole.c new file mode 100644 index 000000000..6138a1653 --- /dev/null +++ b/drivers/firmware/google/memconsole.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * memconsole.c + * + * Architecture-independent parts of the memory based BIOS console. + * + * Copyright 2017 Google Inc. + */ + +#include +#include +#include + +#include "memconsole.h" + +static ssize_t memconsole_read(struct file *filp, struct kobject *kobp, + const struct bin_attribute *bin_attr, char *buf, + loff_t pos, size_t count) +{ + ssize_t (*memconsole_read_func)(char *, loff_t, size_t); + + memconsole_read_func = bin_attr->private; + if (WARN_ON_ONCE(!memconsole_read_func)) + return -EIO; + + return memconsole_read_func(buf, pos, count); +} + +static struct bin_attribute memconsole_bin_attr = { + .attr = {.name = "log", .mode = 0444}, + .read = memconsole_read, +}; + +void memconsole_setup(ssize_t (*read_func)(char *, loff_t, size_t)) +{ + memconsole_bin_attr.private = read_func; +} +EXPORT_SYMBOL(memconsole_setup); + +int memconsole_sysfs_init(void) +{ + return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr); +} +EXPORT_SYMBOL(memconsole_sysfs_init); + +void memconsole_exit(void) +{ + sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr); +} +EXPORT_SYMBOL(memconsole_exit); + +MODULE_AUTHOR("Google, Inc."); +MODULE_DESCRIPTION("Architecture-independent parts of the memory based BIOS console"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1