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/acpi/ec_sys.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 drivers/acpi/ec_sys.c (limited to 'drivers/acpi/ec_sys.c') diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c new file mode 100644 index 000000000..c074a0fae --- /dev/null +++ b/drivers/acpi/ec_sys.c @@ -0,0 +1,144 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ec_sys.c + * + * Copyright (C) 2010 SUSE Products GmbH/Novell + * Author: + * Thomas Renninger + */ + +#include +#include +#include +#include +#include +#include "internal.h" + +MODULE_AUTHOR("Thomas Renninger "); +MODULE_DESCRIPTION("ACPI EC sysfs access driver"); +MODULE_LICENSE("GPL"); + +static bool write_support; +module_param_hw(write_support, bool, other, 0644); +MODULE_PARM_DESC(write_support, "Dangerous, reboot and removal of battery may " + "be needed."); + +#define EC_SPACE_SIZE 256 + +static struct dentry *acpi_ec_debugfs_dir; + +static ssize_t acpi_ec_read_io(struct file *f, char __user *buf, + size_t count, loff_t *off) +{ + /* Use this if support reading/writing multiple ECs exists in ec.c: + * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private; + */ + unsigned int size = EC_SPACE_SIZE; + loff_t init_off = *off; + int err = 0; + + if (*off >= size) + return 0; + if (*off + count >= size) { + size -= *off; + count = size; + } else + size = count; + + while (size) { + u8 byte_read; + err = ec_read(*off, &byte_read); + if (err) + return err; + if (put_user(byte_read, buf + *off - init_off)) { + if (*off - init_off) + return *off - init_off; /* partial read */ + return -EFAULT; + } + *off += 1; + size--; + } + return count; +} + +static ssize_t acpi_ec_write_io(struct file *f, const char __user *buf, + size_t count, loff_t *off) +{ + /* Use this if support reading/writing multiple ECs exists in ec.c: + * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private; + */ + + unsigned int size = count; + loff_t init_off = *off; + int err = 0; + + if (!write_support) + return -EINVAL; + + if (*off >= EC_SPACE_SIZE) + return 0; + if (*off + count >= EC_SPACE_SIZE) { + size = EC_SPACE_SIZE - *off; + count = size; + } + + while (size) { + u8 byte_write; + if (get_user(byte_write, buf + *off - init_off)) { + if (*off - init_off) + return *off - init_off; /* partial write */ + return -EFAULT; + } + err = ec_write(*off, byte_write); + if (err) + return err; + + *off += 1; + size--; + } + return count; +} + +static const struct file_operations acpi_ec_io_ops = { + .owner = THIS_MODULE, + .open = simple_open, + .read = acpi_ec_read_io, + .write = acpi_ec_write_io, + .llseek = default_llseek, +}; + +static void acpi_ec_add_debugfs(struct acpi_ec *ec, unsigned int ec_device_count) +{ + struct dentry *dev_dir; + char name[64]; + umode_t mode = 0400; + + if (ec_device_count == 0) + acpi_ec_debugfs_dir = debugfs_create_dir("ec", NULL); + + sprintf(name, "ec%u", ec_device_count); + dev_dir = debugfs_create_dir(name, acpi_ec_debugfs_dir); + + debugfs_create_x32("gpe", 0444, dev_dir, &first_ec->gpe); + debugfs_create_bool("use_global_lock", 0444, dev_dir, + &first_ec->global_lock); + + if (write_support) + mode = 0600; + debugfs_create_file("io", mode, dev_dir, ec, &acpi_ec_io_ops); +} + +static int __init acpi_ec_sys_init(void) +{ + if (first_ec) + acpi_ec_add_debugfs(first_ec, 0); + return 0; +} + +static void __exit acpi_ec_sys_exit(void) +{ + debugfs_remove_recursive(acpi_ec_debugfs_dir); +} + +module_init(acpi_ec_sys_init); +module_exit(acpi_ec_sys_exit); -- cgit v1.3.1