Re: [PATCH] allow file system to configure for no leases

[Peter Staubach <staubach@redhat.com>]

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Trond Myklebust wrote:
> On Tue, 2007-06-05 at 15:10 -0400, Peter Staubach wrote:
>   
>> Hi.
>>
>> Attached is a small patch to allow file systems to inform the file
>> system independent layers that they don't support file leases.
>>
>> The problem is that some file system such as NFSv2 and NFSv3 do
>> not have sufficient support to be able to support leases correctly.
>> In particular for these two file systems, there is no over the wire
>> protocol support.
>>
>> Currently, these two file systems fail the fcntl(F_SETLEASE) call
>> accidently, due to a reference counting difference.  These file systems
>> should fail more consciously, with a proper error to indicate that
>> the call is invalid for them.
>>
>>     Thanx...
>>
>>        ps
>> plain text document attachment (devel.tototoday)
>> --- linux-2.6.21.i686/fs/nfs/super.c.org
>> +++ linux-2.6.21.i686/fs/nfs/super.c
>> @@ -522,6 +522,9 @@ static inline void nfs_initialise_sb(str
>>  
>>  	sb->s_magic = NFS_SUPER_MAGIC;
>>  
>> +	if (server->nfs_client->cl_nfsversion < 4)
>> +		sb->s_flags |= MS_NO_LEASES;
>> +
>>     
>
> This should be unconditional since we have no support for "lease locks"
> under NFSv4 either. The NFSv4 concept of leases and delegations is very
> different, since it is really tied to the ability to cache data.

No problem.  I wasn't sure, what with the changes that Bruce Fields
is constructing.

Attached is the simplified version.

    Thanx...

       ps

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--- linux-2.6.21.i686/fs/nfs/super.c.org
+++ linux-2.6.21.i686/fs/nfs/super.c
@@ -522,6 +522,8 @@ static inline void nfs_initialise_sb(str
 
 	sb->s_magic = NFS_SUPER_MAGIC;
 
+	sb->s_flags |= MS_NO_LEASES;
+
 	/* We probably want something more informative here */
 	snprintf(sb->s_id, sizeof(sb->s_id),
 		 "%x:%x", MAJOR(sb->s_dev), MINOR(sb->s_dev));
--- linux-2.6.21.i686/fs/locks.c.org
+++ linux-2.6.21.i686/fs/locks.c
@@ -1493,6 +1493,8 @@ int fcntl_setlease(unsigned int fd, stru
 	error = security_file_lock(filp, arg);
 	if (error)
 		return error;
+	if (IS_NO_LEASES(inode))
+		return -EINVAL;
 
 	locks_init_lock(&fl);
 	error = lease_init(filp, arg, &fl);
--- linux-2.6.21.i686/include/linux/fs.h.org
+++ linux-2.6.21.i686/include/linux/fs.h
@@ -121,6 +121,7 @@ extern int dir_notify_enable;
 #define MS_SLAVE	(1<<19)	/* change to slave */
 #define MS_SHARED	(1<<20)	/* change to shared */
 #define MS_RELATIME	(1<<21)	/* Update atime relative to mtime/ctime. */
+#define MS_NO_LEASES	(1<<22)	/* fs does not support leases */
 #define MS_ACTIVE	(1<<30)
 #define MS_NOUSER	(1<<31)
 
@@ -180,6 +181,7 @@ extern int dir_notify_enable;
 #define IS_NOCMTIME(inode)	((inode)->i_flags & S_NOCMTIME)
 #define IS_SWAPFILE(inode)	((inode)->i_flags & S_SWAPFILE)
 #define IS_PRIVATE(inode)	((inode)->i_flags & S_PRIVATE)
+#define IS_NO_LEASES(inode)	__IS_FLG(inode, MS_NO_LEASES)
 
 /* the read-only stuff doesn't really belong here, but any other place is
    probably as bad and I don't want to create yet another include file. */