![David Howells](/assets/img/avatar_default.png)
Implement the ability for filesystems to log error, warning and informational messages through the fs_context. These can be extracted by userspace by reading from an fd created by fsopen(). Error messages are prefixed with "e ", warnings with "w " and informational messages with "i ". Inside the kernel, formatted messages are malloc'd but unformatted messages are not copied if they're either in the core .rodata section or in the .rodata section of the filesystem module pinned by fs_context::fs_type. The messages are only good till the fs_type is released. Note that the logging object is shared between duplicated fs_context structures. This is so that such as NFS which do a mount within a mount can get at least some of the errors from the inner mount. Five logging functions are provided for this: (1) void logfc(struct fs_context *fc, const char *fmt, ...); This logs a message into the context. If the buffer is full, the earliest message is discarded. (2) void errorf(fc, fmt, ...); This wraps logfc() to log an error. (3) void invalf(fc, fmt, ...); This wraps errorf() and returns -EINVAL for convenience. (4) void warnf(fc, fmt, ...); This wraps logfc() to log a warning. (5) void infof(fc, fmt, ...); This wraps logfc() to log an informational message. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
213 lines
7.1 KiB
C
213 lines
7.1 KiB
C
/* Filesystem superblock creation and reconfiguration context.
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*
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* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#ifndef _LINUX_FS_CONTEXT_H
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#define _LINUX_FS_CONTEXT_H
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#include <linux/kernel.h>
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#include <linux/refcount.h>
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#include <linux/errno.h>
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#include <linux/security.h>
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#include <linux/mutex.h>
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struct cred;
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struct dentry;
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struct file_operations;
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struct file_system_type;
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struct mnt_namespace;
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struct net;
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struct pid_namespace;
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struct super_block;
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struct user_namespace;
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struct vfsmount;
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struct path;
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enum fs_context_purpose {
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FS_CONTEXT_FOR_MOUNT, /* New superblock for explicit mount */
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FS_CONTEXT_FOR_SUBMOUNT, /* New superblock for automatic submount */
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FS_CONTEXT_FOR_RECONFIGURE, /* Superblock reconfiguration (remount) */
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};
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/*
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* Userspace usage phase for fsopen/fspick.
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*/
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enum fs_context_phase {
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FS_CONTEXT_CREATE_PARAMS, /* Loading params for sb creation */
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FS_CONTEXT_CREATING, /* A superblock is being created */
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FS_CONTEXT_AWAITING_MOUNT, /* Superblock created, awaiting fsmount() */
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FS_CONTEXT_AWAITING_RECONF, /* Awaiting initialisation for reconfiguration */
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FS_CONTEXT_RECONF_PARAMS, /* Loading params for reconfiguration */
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FS_CONTEXT_RECONFIGURING, /* Reconfiguring the superblock */
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FS_CONTEXT_FAILED, /* Failed to correctly transition a context */
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};
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/*
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* Type of parameter value.
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*/
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enum fs_value_type {
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fs_value_is_undefined,
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fs_value_is_flag, /* Value not given a value */
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fs_value_is_string, /* Value is a string */
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fs_value_is_blob, /* Value is a binary blob */
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fs_value_is_filename, /* Value is a filename* + dirfd */
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fs_value_is_filename_empty, /* Value is a filename* + dirfd + AT_EMPTY_PATH */
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fs_value_is_file, /* Value is a file* */
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};
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/*
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* Configuration parameter.
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*/
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struct fs_parameter {
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const char *key; /* Parameter name */
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enum fs_value_type type:8; /* The type of value here */
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union {
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char *string;
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void *blob;
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struct filename *name;
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struct file *file;
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};
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size_t size;
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int dirfd;
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};
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/*
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* Filesystem context for holding the parameters used in the creation or
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* reconfiguration of a superblock.
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*
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* Superblock creation fills in ->root whereas reconfiguration begins with this
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* already set.
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*
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* See Documentation/filesystems/mounting.txt
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*/
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struct fs_context {
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const struct fs_context_operations *ops;
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struct mutex uapi_mutex; /* Userspace access mutex */
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struct file_system_type *fs_type;
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void *fs_private; /* The filesystem's context */
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struct dentry *root; /* The root and superblock */
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struct user_namespace *user_ns; /* The user namespace for this mount */
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struct net *net_ns; /* The network namespace for this mount */
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const struct cred *cred; /* The mounter's credentials */
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struct fc_log *log; /* Logging buffer */
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const char *source; /* The source name (eg. dev path) */
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const char *subtype; /* The subtype to set on the superblock */
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void *security; /* Linux S&M options */
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void *s_fs_info; /* Proposed s_fs_info */
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unsigned int sb_flags; /* Proposed superblock flags (SB_*) */
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unsigned int sb_flags_mask; /* Superblock flags that were changed */
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unsigned int lsm_flags; /* Information flags from the fs to the LSM */
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enum fs_context_purpose purpose:8;
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enum fs_context_phase phase:8; /* The phase the context is in */
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bool need_free:1; /* Need to call ops->free() */
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bool global:1; /* Goes into &init_user_ns */
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};
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struct fs_context_operations {
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void (*free)(struct fs_context *fc);
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int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
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int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
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int (*parse_monolithic)(struct fs_context *fc, void *data);
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int (*get_tree)(struct fs_context *fc);
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int (*reconfigure)(struct fs_context *fc);
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};
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/*
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* fs_context manipulation functions.
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*/
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extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
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unsigned int sb_flags);
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extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
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unsigned int sb_flags,
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unsigned int sb_flags_mask);
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extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
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struct dentry *reference);
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extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
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extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
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extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
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const char *value, size_t v_size);
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extern int generic_parse_monolithic(struct fs_context *fc, void *data);
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extern int vfs_get_tree(struct fs_context *fc);
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extern void put_fs_context(struct fs_context *fc);
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/*
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* sget() wrapper to be called from the ->get_tree() op.
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*/
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enum vfs_get_super_keying {
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vfs_get_single_super, /* Only one such superblock may exist */
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vfs_get_keyed_super, /* Superblocks with different s_fs_info keys may exist */
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vfs_get_independent_super, /* Multiple independent superblocks may exist */
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};
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extern int vfs_get_super(struct fs_context *fc,
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enum vfs_get_super_keying keying,
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int (*fill_super)(struct super_block *sb,
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struct fs_context *fc));
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extern const struct file_operations fscontext_fops;
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/*
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* Mount error, warning and informational message logging. This structure is
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* shareable between a mount and a subordinate mount.
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*/
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struct fc_log {
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refcount_t usage;
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u8 head; /* Insertion index in buffer[] */
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u8 tail; /* Removal index in buffer[] */
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u8 need_free; /* Mask of kfree'able items in buffer[] */
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struct module *owner; /* Owner module for strings that don't then need freeing */
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char *buffer[8];
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};
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extern __attribute__((format(printf, 2, 3)))
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void logfc(struct fs_context *fc, const char *fmt, ...);
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/**
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* infof - Store supplementary informational message
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* @fc: The context in which to log the informational message
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* @fmt: The format string
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*
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* Store the supplementary informational message for the process if the process
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* has enabled the facility.
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*/
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#define infof(fc, fmt, ...) ({ logfc(fc, "i "fmt, ## __VA_ARGS__); })
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/**
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* warnf - Store supplementary warning message
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* @fc: The context in which to log the error message
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* @fmt: The format string
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*
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* Store the supplementary warning message for the process if the process has
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* enabled the facility.
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*/
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#define warnf(fc, fmt, ...) ({ logfc(fc, "w "fmt, ## __VA_ARGS__); })
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/**
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* errorf - Store supplementary error message
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* @fc: The context in which to log the error message
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* @fmt: The format string
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*
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* Store the supplementary error message for the process if the process has
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* enabled the facility.
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*/
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#define errorf(fc, fmt, ...) ({ logfc(fc, "e "fmt, ## __VA_ARGS__); })
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/**
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* invalf - Store supplementary invalid argument error message
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* @fc: The context in which to log the error message
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* @fmt: The format string
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*
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* Store the supplementary error message for the process if the process has
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* enabled the facility and return -EINVAL.
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*/
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#define invalf(fc, fmt, ...) ({ errorf(fc, fmt, ## __VA_ARGS__); -EINVAL; })
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#endif /* _LINUX_FS_CONTEXT_H */
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