4ed5e82fe7
Currently remouting superblock read-only is racy in a major way. With the per mount read-only infrastructure it is now possible to prevent most races, which this patch attempts. Before starting the remount read-only, iterate through all mounts belonging to the superblock and if none of them have any pending writes, set sb->s_readonly_remount. This indicates that remount is in progress and no further write requests are allowed. If the remount succeeds set MS_RDONLY and reset s_readonly_remount. If the remounting is unsuccessful just reset s_readonly_remount. This can result in transient EROFS errors, despite the fact the remount failed. Unfortunately hodling off writes is difficult as remount itself may touch the filesystem (e.g. through load_nls()) which would deadlock. A later patch deals with delayed writes due to nlink going to zero. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
/* fs/ internal definitions
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*
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* Copyright (C) 2006 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 License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/lglock.h>
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struct super_block;
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struct file_system_type;
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struct linux_binprm;
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struct path;
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struct mount;
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/*
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* block_dev.c
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*/
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#ifdef CONFIG_BLOCK
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extern void __init bdev_cache_init(void);
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extern int __sync_blockdev(struct block_device *bdev, int wait);
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#else
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static inline void bdev_cache_init(void)
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{
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}
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static inline int __sync_blockdev(struct block_device *bdev, int wait)
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{
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return 0;
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}
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#endif
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/*
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* char_dev.c
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*/
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extern void __init chrdev_init(void);
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/*
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* namespace.c
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*/
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extern int copy_mount_options(const void __user *, unsigned long *);
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extern int copy_mount_string(const void __user *, char **);
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extern struct vfsmount *lookup_mnt(struct path *);
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extern int finish_automount(struct vfsmount *, struct path *);
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extern void mnt_make_longterm(struct vfsmount *);
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extern void mnt_make_shortterm(struct vfsmount *);
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extern int sb_prepare_remount_readonly(struct super_block *);
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extern void __init mnt_init(void);
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DECLARE_BRLOCK(vfsmount_lock);
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/*
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* fs_struct.c
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*/
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extern void chroot_fs_refs(struct path *, struct path *);
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/*
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* file_table.c
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*/
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extern void file_sb_list_add(struct file *f, struct super_block *sb);
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extern void file_sb_list_del(struct file *f);
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extern void mark_files_ro(struct super_block *);
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extern struct file *get_empty_filp(void);
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/*
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* super.c
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*/
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extern int do_remount_sb(struct super_block *, int, void *, int);
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extern bool grab_super_passive(struct super_block *sb);
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extern struct dentry *mount_fs(struct file_system_type *,
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int, const char *, void *);
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extern struct super_block *user_get_super(dev_t);
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/*
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* open.c
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*/
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struct nameidata;
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extern struct file *nameidata_to_filp(struct nameidata *);
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extern void release_open_intent(struct nameidata *);
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struct open_flags {
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int open_flag;
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umode_t mode;
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int acc_mode;
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int intent;
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};
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extern struct file *do_filp_open(int dfd, const char *pathname,
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const struct open_flags *op, int lookup_flags);
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extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
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const char *, const struct open_flags *, int lookup_flags);
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extern long do_handle_open(int mountdirfd,
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struct file_handle __user *ufh, int open_flag);
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/*
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* inode.c
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*/
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extern spinlock_t inode_sb_list_lock;
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/*
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* fs-writeback.c
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*/
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extern void inode_wb_list_del(struct inode *inode);
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extern int get_nr_dirty_inodes(void);
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extern void evict_inodes(struct super_block *);
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extern int invalidate_inodes(struct super_block *, bool);
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/*
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* dcache.c
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*/
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extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
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