7b7b1ace2d
The way we currently deal with quota and process accounting that might keep vfsmount busy at umount time is inherently broken; we try to turn them off just in case (not quite correctly, at that) and a) pray umount doesn't fail (otherwise they'll stay turned off) b) pray nobody doesn anything funny just as we turn quota off Moreover, LSM provides hooks for doing the same sort of broken logics. The proper way to deal with that is to introduce the second kind of reference to vfsmount. Semantics: - when the last normal reference is dropped, all special ones are converted to normal ones and if there had been any, cleanup is done. - normal reference can be cloned into a special one - special reference can be converted to normal one; that's a no-op if we'd already passed the point of no return (i.e. mntput() had converted special references to normal and started cleanup). The way it works: e.g. starting process accounting converts the vfsmount reference pinned by the opened file into special one and turns it back to normal when it gets shut down; acct_auto_close() is done when no normal references are left. That way it does *not* obstruct umount(2) and it silently gets turned off when the last normal reference to vfsmount is gone. Which is exactly what we want... The same should be done by LSM module that holds some internal references to vfsmount and wants to shut them down on umount - it should make them special and security_sb_umount_close() will be called exactly when the last normal reference to vfsmount is gone. quota handling is even simpler - we don't use normal file IO anymore, so there's no need to hold vfsmounts at all. DQUOT_OFF() is done from deactivate_super(), where it really belongs. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
78 lines
2.1 KiB
C
78 lines
2.1 KiB
C
/*
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*
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* Definitions for mount interface. This describes the in the kernel build
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* linkedlist with mounted filesystems.
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*
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* Author: Marco van Wieringen <mvw@planets.elm.net>
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*
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* Version: $Id: mount.h,v 2.0 1996/11/17 16:48:14 mvw Exp mvw $
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*
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*/
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#ifndef _LINUX_MOUNT_H
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#define _LINUX_MOUNT_H
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#ifdef __KERNEL__
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <asm/atomic.h>
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#define MNT_NOSUID 1
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#define MNT_NODEV 2
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#define MNT_NOEXEC 4
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struct vfsmount
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{
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struct list_head mnt_hash;
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struct vfsmount *mnt_parent; /* fs we are mounted on */
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struct dentry *mnt_mountpoint; /* dentry of mountpoint */
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struct dentry *mnt_root; /* root of the mounted tree */
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struct super_block *mnt_sb; /* pointer to superblock */
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struct list_head mnt_mounts; /* list of children, anchored here */
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struct list_head mnt_child; /* and going through their mnt_child */
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atomic_t mnt_count;
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int mnt_flags;
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int mnt_expiry_mark; /* true if marked for expiry */
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char *mnt_devname; /* Name of device e.g. /dev/dsk/hda1 */
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struct list_head mnt_list;
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struct list_head mnt_expire; /* link in fs-specific expiry list */
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struct namespace *mnt_namespace; /* containing namespace */
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int mnt_pinned;
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};
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static inline struct vfsmount *mntget(struct vfsmount *mnt)
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{
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if (mnt)
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atomic_inc(&mnt->mnt_count);
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return mnt;
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}
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extern void mntput_no_expire(struct vfsmount *mnt);
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extern void mnt_pin(struct vfsmount *mnt);
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extern void mnt_unpin(struct vfsmount *mnt);
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static inline void mntput(struct vfsmount *mnt)
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{
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if (mnt) {
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mnt->mnt_expiry_mark = 0;
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mntput_no_expire(mnt);
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}
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}
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extern void free_vfsmnt(struct vfsmount *mnt);
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extern struct vfsmount *alloc_vfsmnt(const char *name);
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extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
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const char *name, void *data);
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struct nameidata;
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extern int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
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int mnt_flags, struct list_head *fslist);
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extern void mark_mounts_for_expiry(struct list_head *mounts);
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extern spinlock_t vfsmount_lock;
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extern dev_t name_to_dev_t(char *name);
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#endif
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#endif /* _LINUX_MOUNT_H */
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