Commit 9e8925b6 authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: Allow disabling mandatory locking at compile time 



Mandatory locking appears to be almost unused and buggy and there
appears no real interest in doing anything with it.  Since effectively
no one uses the code and since the code is buggy let's allow it to be
disabled at compile time.  I would just suggest removing the code but
undoubtedly that will break some piece of userspace code somewhere.

For the distributions that don't care about this piece of code
this gives a nice starting point to make mandatory locking go away.

Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jeff Layton <jeff.layton@primarydata.com>
Cc: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarJeff Layton <jeff.layton@primarydata.com>
parent 8005c49d

fs/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -67,6 +67,16 @@ config FILE_LOCKING 
          for filesystems like NFS and for the flock() system

          call. Disabling this option saves about 11k.



config MANDATORY_FILE_LOCKING

	bool "Enable Mandatory file locking"

	depends on FILE_LOCKING

	default y

	help

	  This option enables files appropriately marked files on appropriely

	  mounted filesystems to support mandatory locking.



	  To the best of my knowledge this is dead code that no one cares about.



source "fs/notify/Kconfig"



source "fs/quota/Kconfig"

fs/locks.c

+2 −0
Original line number Diff line number Diff line
@@ -1191,6 +1191,7 @@ static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl) 
	return error;

}



#ifdef CONFIG_MANDATORY_FILE_LOCKING

/**

 * locks_mandatory_locked - Check for an active lock

 * @file: the file to check
@@ -1289,6 +1290,7 @@ int locks_mandatory_area(int read_write, struct inode *inode, 
}



EXPORT_SYMBOL(locks_mandatory_area);

#endif /* CONFIG_MANDATORY_FILE_LOCKING */



static void lease_clear_pending(struct file_lock *fl, int arg)

{

fs/namespace.c

+10 −0
Original line number Diff line number Diff line
@@ -1584,6 +1584,14 @@ static inline bool may_mount(void) 
	return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);

}



static inline bool may_mandlock(void)

{

#ifndef	CONFIG_MANDATORY_FILE_LOCKING

	return false;

#endif

	return true;

}



/*

 * Now umount can handle mount points as well as block devices.

 * This is important for filesystems which use unnamed block devices.
@@ -2677,6 +2685,8 @@ long do_mount(const char *dev_name, const char __user *dir_name, 
				   type_page, flags, data_page);

	if (!retval && !may_mount())

		retval = -EPERM;

	if (!retval && (flags & MS_MANDLOCK) && !may_mandlock())

		retval = -EPERM;

	if (retval)

		goto dput_out;

include/linux/fs.h

+40 −34
Original line number Diff line number Diff line
@@ -2030,7 +2030,7 @@ extern struct kobject *fs_kobj; 
#define FLOCK_VERIFY_READ  1

#define FLOCK_VERIFY_WRITE 2



#ifdef CONFIG_FILE_LOCKING

#ifdef CONFIG_MANDATORY_FILE_LOCKING

extern int locks_mandatory_locked(struct file *);

extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);
@@ -2075,6 +2075,45 @@ static inline int locks_verify_truncate(struct inode *inode, 
	return 0;

}



#else /* !CONFIG_MANDATORY_FILE_LOCKING */



static inline int locks_mandatory_locked(struct file *file)

{

	return 0;

}



static inline int locks_mandatory_area(int rw, struct inode *inode,

				       struct file *filp, loff_t offset,

				       size_t count)

{

	return 0;

}



static inline int __mandatory_lock(struct inode *inode)

{

	return 0;

}



static inline int mandatory_lock(struct inode *inode)

{

	return 0;

}



static inline int locks_verify_locked(struct file *file)

{

	return 0;

}



static inline int locks_verify_truncate(struct inode *inode, struct file *filp,

					size_t size)

{

	return 0;

}



#endif /* CONFIG_MANDATORY_FILE_LOCKING */





#ifdef CONFIG_FILE_LOCKING

static inline int break_lease(struct inode *inode, unsigned int mode)

{

	/*
@@ -2136,39 +2175,6 @@ static inline int break_layout(struct inode *inode, bool wait) 
}



#else /* !CONFIG_FILE_LOCKING */

static inline int locks_mandatory_locked(struct file *file)

{

	return 0;

}



static inline int locks_mandatory_area(int rw, struct inode *inode,

				       struct file *filp, loff_t offset,

				       size_t count)

{

	return 0;

}



static inline int __mandatory_lock(struct inode *inode)

{

	return 0;

}



static inline int mandatory_lock(struct inode *inode)

{

	return 0;

}



static inline int locks_verify_locked(struct file *file)

{

	return 0;

}



static inline int locks_verify_truncate(struct inode *inode, struct file *filp,

					size_t size)

{

	return 0;

}



static inline int break_lease(struct inode *inode, unsigned int mode)

{

	return 0;

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