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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 /*
     22  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 #ifndef	_SYS_FS_ZFS_RLOCK_H
     27 #define	_SYS_FS_ZFS_RLOCK_H
     28 
     29 #ifdef	__cplusplus
     30 extern "C" {
     31 #endif
     32 
     33 #ifdef _KERNEL
     34 
     35 #include <sys/zfs_znode.h>
     36 
     37 typedef enum {
     38 	RL_READER,
     39 	RL_WRITER,
     40 	RL_APPEND
     41 } rl_type_t;
     42 
     43 typedef struct rl {
     44 	znode_t *r_zp;		/* znode this lock applies to */
     45 	avl_node_t r_node;	/* avl node link */
     46 	uint64_t r_off;		/* file range offset */
     47 	uint64_t r_len;		/* file range length */
     48 	uint_t r_cnt;		/* range reference count in tree */
     49 	rl_type_t r_type;	/* range type */
     50 	kcondvar_t r_wr_cv;	/* cv for waiting writers */
     51 	kcondvar_t r_rd_cv;	/* cv for waiting readers */
     52 	uint8_t r_proxy;	/* acting for original range */
     53 	uint8_t r_write_wanted;	/* writer wants to lock this range */
     54 	uint8_t r_read_wanted;	/* reader wants to lock this range */
     55 } rl_t;
     56 
     57 /*
     58  * Lock a range (offset, length) as either shared (RL_READER)
     59  * or exclusive (RL_WRITER or RL_APPEND).  RL_APPEND is a special type that
     60  * is converted to RL_WRITER that specified to lock from the start of the
     61  * end of file.  Returns the range lock structure.
     62  */
     63 rl_t *zfs_range_lock(znode_t *zp, uint64_t off, uint64_t len, rl_type_t type);
     64 rl_t *zfs_range_lock_try(znode_t *zp, uint64_t off, uint64_t len, rl_type_t type);
     65 
     66 /* Unlock range and destroy range lock structure. */
     67 void zfs_range_unlock(rl_t *rl);
     68 
     69 /*
     70  * Reduce range locked as RW_WRITER from whole file to specified range.
     71  * Asserts the whole file was previously locked.
     72  */
     73 void zfs_range_reduce(rl_t *rl, uint64_t off, uint64_t len);
     74 
     75 /*
     76  * AVL comparison function used to order range locks
     77  * Locks are ordered on the start offset of the range.
     78  */
     79 int zfs_range_compare(const void *arg1, const void *arg2);
     80 
     81 #endif /* _KERNEL */
     82 
     83 #ifdef	__cplusplus
     84 }
     85 #endif
     86 
     87 #endif	/* _SYS_FS_ZFS_RLOCK_H */
     88