/*
 * Copyright (c) 2000-2016 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)buf.h	8.9 (Berkeley) 3/30/95
 */

#ifndef _SYS_BUF_H_
#define _SYS_BUF_H_

#include <sys/cdefs.h>
#include <sys/kernel_types.h>
#include <sys/ucred.h>
#include <mach/memory_object_types.h>


#define B_WRITE         0x00000000      /* Write buffer (pseudo flag). */
#define B_READ          0x00000001      /* Read buffer. */
#define B_ASYNC         0x00000002      /* Start I/O, do not wait. */
#define B_NOCACHE       0x00000004      /* Do not cache block after use. */
#define B_DELWRI        0x00000008      /* Delay I/O until buffer reused. */
#define B_LOCKED        0x00000010      /* Locked in core (not reusable). */
#define B_PHYS          0x00000020      /* I/O to user memory. */
#define B_CLUSTER       0x00000040      /* UPL based I/O generated by cluster layer */
#define B_PAGEIO        0x00000080      /* Page in/out */
#define B_META          0x00000100      /* buffer contains meta-data. */
#define B_RAW           0x00000200      /* Set by physio for raw transfers. */
#define B_FUA           0x00000400      /* Write-through disk cache(if supported) */
#define B_PASSIVE       0x00000800      /* PASSIVE I/Os are ignored by THROTTLE I/O */
#define B_IOSTREAMING   0x00001000      /* sequential access pattern detected */
#define B_THROTTLED_IO  0x00002000      /* low priority I/O (deprecated) */
#define B_ENCRYPTED_IO  0x00004000      /* Encrypted I/O */
#define B_STATICCONTENT 0x00008000      /* Buffer is likely to remain unaltered */

/*
 * make sure to check when adding flags that
 * that the new flags don't overlap the definitions
 * in buf_internal.h
 */

__BEGIN_DECLS

/*!
 *  @function buf_markaged
 *  @abstract Mark a buffer as "aged," i.e. as a good candidate to be discarded and reused after buf_brelse().
 *  @param bp Buffer to mark.
 */
void    buf_markaged(buf_t bp);

/*!
 *  @function buf_markinvalid
 *  @abstract Mark a buffer as not having valid data and being ready for immediate reuse after buf_brelse().
 *  @param bp Buffer to mark.
 */
void    buf_markinvalid(buf_t bp);

/*!
 *  @function buf_markdelayed
 *  @abstract Mark a buffer as a delayed write: mark it dirty without actually scheduling I/O.
 *  @discussion Data will be flushed to disk at some later time, not with brelse(). A sync()/fsync()
 *  or pressure necessitating reuse of the buffer will cause it to be written back to disk.
 *  @param bp Buffer to mark.
 */
void    buf_markdelayed(buf_t bp);

void    buf_markclean(buf_t);

/*!
 *  @function buf_markeintr
 *  @abstract Mark a buffer as having been interrupted during I/O.
 *  @discussion Waiters for I/O to complete (buf_biowait()) will return with EINTR when woken up.
 *  buf_markeintr does not itself do a wakeup.
 *  @param bp Buffer to mark.
 */
void    buf_markeintr(buf_t bp);

/*!
 *  @function buf_markfua
 *  @abstract Mark a buffer for write through disk cache, if disk supports it.
 *  @param bp Buffer to mark.
 */
void    buf_markfua(buf_t bp);

/*!
 *  @function buf_fua
 *  @abstract Check if a buffer is marked for write through disk caches.
 *  @param bp Buffer to test.
 *  @return Nonzero if buffer is marked for write-through, 0 if not.
 */
int     buf_fua(buf_t bp);

/*!
 *  @function buf_valid
 *  @abstract Check if a buffer contains valid data.
 *  @param bp Buffer to test.
 *  @return Nonzero if buffer has valid data, 0 if not.
 */
int     buf_valid(buf_t bp);

/*!
 *  @function buf_fromcache
 *  @abstract Check if a buffer's data was found in core.
 *  @discussion Will return truth after a buf_getblk that finds a valid buffer in the cache or the relevant
 *  data in core (but not in a buffer).
 *  @param bp Buffer to test.
 *  @return Nonzero if we got this buffer's data without doing I/O, 0 if not.
 */
int     buf_fromcache(buf_t bp);

/*!
 *  @function buf_upl
 *  @abstract Get the upl (Universal Page List) associated with a buffer.
 *  @discussion Buffers allocated with buf_alloc() are not returned with a upl, and
 *  traditional buffers only have a upl while an I/O is in progress.
 *  @param bp Buffer whose upl to grab.
 *  @return Buffer's upl if it has one, else NULL.
 */
void *  buf_upl(buf_t bp);

/*!
 *  @function buf_uploffset
 *  @abstract Get the offset into a UPL at which this buffer begins.
 *  @discussion This function should only be called on iobufs, i.e. buffers allocated with buf_alloc().
 *  @param bp Buffer whose uploffset to grab.
 *  @return Buffer's uploffset--does not check whether that value makes sense for this buffer.
 */
uint32_t buf_uploffset(buf_t bp);

/*!
 *  @function buf_rcred
 *  @abstract Get the credential associated with a buffer for reading.
 *  @discussion No reference is taken; if the credential is to be held on to persistently, an additional
 *  reference must be taken with kauth_cred_ref.
 *  @param bp Buffer whose credential to grab.
 *  @return Credential if it exists, else NULL.
 */
kauth_cred_t buf_rcred(buf_t bp);

/*!
 *  @function buf_wcred
 *  @abstract Get the credential associated with a buffer for writing.
 *  @discussion No reference is taken; if the credential is to be held on to persistently, an additional
 *  reference must be taken with kauth_cred_ref.
 *  @param bp Buffer whose credential to grab.
 *  @return Credential if it exists, else NULL.
 */
kauth_cred_t buf_wcred(buf_t bp);

/*!
 *  @function buf_proc
 *  @abstract Get the process associated with this buffer.
 *  @discussion buf_proc() will generally return NULL; a process is currently only associated with
 *  a buffer in the event of a physio() call.
 *  @param bp Buffer whose associated process to find.
 *  @return Associated process, possibly NULL.
 */
proc_t  buf_proc(buf_t bp);

/*!
 *  @function buf_dirtyoff
 *  @abstract Get the starting offset of the dirty region associated with a buffer.
 *  @discussion The dirty offset is zero unless someone explicitly calls buf_setdirtyoff() (which the kernel does not).
 *  @param bp Buffer whose dirty offset to get.
 *  @return Dirty offset (0 if not explicitly changed).
 */
uint32_t buf_dirtyoff(buf_t bp);

/*!
 *  @function buf_dirtyend
 *  @abstract Get the ending offset of the dirty region associated with a buffer.
 *  @discussion If the buffer's data was found incore and dirty, the dirty end is the size of the block; otherwise, unless
 *  someone outside of xnu explicitly changes it by calling buf_setdirtyend(), it will be zero.
 *  @param bp Buffer whose dirty end to get.
 *  @return 0 if buffer is found clean; size of buffer if found dirty.  Can be set to any value by callers of buf_setdirtyend().
 */
uint32_t buf_dirtyend(buf_t bp);

/*!
 *  @function buf_setdirtyoff
 *  @abstract Set the starting offset of the dirty region associated with a buffer.
 *  @discussion This value is zero unless someone set it explicitly.
 *  @param bp Buffer whose dirty end to set.
 */
void    buf_setdirtyoff(buf_t bp, uint32_t);

/*!
 *  @function buf_setdirtyend
 *  @abstract Set the ending offset of the dirty region associated with a buffer.
 *  @discussion If the buffer's data was found incore and dirty, the dirty end is the size of the block; otherwise, unless
 *  someone outside of xnu explicitly changes it by calling buf_setdirtyend(), it will be zero.
 *  @param bp Buffer whose dirty end to set.
 */
void    buf_setdirtyend(buf_t bp, uint32_t);

/*!
 *  @function buf_error
 *  @abstract Get the error value associated with a buffer.
 *  @discussion Errors are set with buf_seterror().
 *  @param bp Buffer whose error value to retrieve.
 *  @return Error value, directly.
 */
errno_t buf_error(buf_t bp);

/*!
 *  @function buf_seterror
 *  @abstract Set an error value on a buffer.
 *  @param bp Buffer whose error value to set.
 */
void    buf_seterror(buf_t bp, errno_t);

/*!
 *  @function buf_setflags
 *  @abstract Set flags on a buffer.
 *  @discussion buffer_flags |= flags
 *  @param bp Buffer whose flags to set.
 *  @param flags Flags to add to buffer's mask. B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA
 */
void    buf_setflags(buf_t bp, int32_t flags);

/*!
 *  @function buf_clearflags
 *  @abstract Clear flags on a buffer.
 *  @discussion buffer_flags &= ~flags
 *  @param bp Buffer whose flags to clear.
 *  @param flags Flags to remove from buffer's mask. B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA
 */
void    buf_clearflags(buf_t bp, int32_t flags);

/*!
 *  @function buf_flags
 *  @abstract Get flags set on a buffer.
 *  @discussion Valid flags are B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA.
 *  @param bp Buffer whose flags to grab.
 *  @return flags.
 */
int32_t buf_flags(buf_t bp);

/*!
 *  @function buf_reset
 *  @abstract Reset I/O flag state on a buffer.
 *  @discussion Clears current flags on a buffer (internal and external) and allows some new flags to be set.
 *  Used perhaps to prepare an iobuf for reuse.
 *  @param bp Buffer whose flags to grab.
 *  @param flags Flags to set on buffer: B_READ, B_WRITE, B_ASYNC, B_NOCACHE.
 */
void    buf_reset(buf_t bp, int32_t flags);

/*!
 *  @function buf_map
 *  @abstract Get virtual mappings for buffer data.
 *  @discussion For buffers created through buf_getblk() (i.e. traditional buffer cache usage),
 *  buf_map() just returns the address at which data was mapped by but_getblk().  For a B_CLUSTER buffer, i.e. an iobuf
 *  whose upl state is managed manually, there are two possibilities.  If the buffer was created
 *  with an underlying "real" buffer through cluster_bp(), the mapping of the "real" buffer is returned.
 *  Otherwise, the buffer was created with buf_alloc() and buf_setupl() was subsequently called; buf_map()
 *  will call ubc_upl_map() to get a mapping for the buffer's upl and return the start of that mapping
 *  plus the buffer's upl offset (set in buf_setupl()).  In the last case, buf_unmap() must later be called
 *  to tear down the mapping.  NOTE: buf_map() does not set the buffer data pointer; this must be done with buf_setdataptr().
 *  @param bp Buffer whose mapping to find or create.
 *  @param io_addr Destination for mapping address.
 *  @return 0 for success, ENOMEM if unable to map the buffer.
 */
errno_t buf_map(buf_t bp, caddr_t *io_addr);

/*!
 *  @function buf_map_range
 *  @abstract Get virtual mappings for buffer data.
 *  @discussion Similar to buf_map but the focus is on a range
 *  of the UPL. The b_uploffset and b_count control what part of the UPL will be mapped.
 *  This function is paired with buf_unmap_range which must be called from the same
 *  thread.
 *  @param bp Buffer whose mapping to find or create.
 *  @param io_addr Destination for mapping address.
 *  @return 0 for success, ENOMEM if unable to map the buffer.
 */
errno_t buf_map_range(buf_t bp, caddr_t *io_addr);

/*!
 *  @function buf_map_range_with_prot
 *  @abstract Get virtual mappings for buffer data.
 *  @discussion Similar to buf_map_range but also takes protection so that part of the UPL
 *  will be mapped with the requested protection.
 *  This function is paired with buf_unmap_range which must be called from the same
 *  thread.
 *  @param bp Buffer whose mapping to find or create.
 *  @param io_addr Destination for mapping address.
 *  @return 0 for success, ENOMEM if unable to map the buffer.
 */
errno_t buf_map_range_with_prot(buf_t bp, caddr_t *io_addr, vm_prot_t prot);

/*!
 *  @function buf_unmap
 *  @abstract Release mappings for buffer data.
 *  @discussion For buffers created through buf_getblk() (i.e. traditional buffer cache usage),
 *  buf_unmap() does nothing; buf_brelse() will take care of unmapping.  For a B_CLUSTER buffer, i.e. an iobuf
 *  whose upl state is managed manually, there are two possibilities.  If the buffer was created
 *  with an underlying "real" buffer through cluster_bp(), buf_unmap() does nothing; buf_brelse() on the
 *  underlying buffer will tear down the mapping. Otherwise, the buffer was created with buf_alloc() and
 *  buf_setupl() was subsequently called; buf_map() created the mapping.  In this case, buf_unmap() will
 *  unmap the buffer.
 *  @param bp Buffer whose mapping to find or create.
 *  @return 0 for success, EINVAL if unable to unmap buffer.
 */
errno_t buf_unmap(buf_t bp);

/*!
 *  @function buf_unmap_range
 *  @abstract Release mappings for buffer data.
 *  @discussion Similar to buf_unmap but the focus is on a range
 *  of the UPL. The b_uploffset and b_count control what part of the UPL will be unmapped.
 *  This function must be called from the same thread that called the corresponding
 *  buf_map_range/buf_map_range_with_prot.
 *  @param bp Buffer whose mapping to find or create.
 *  @return 0 for success, EINVAL if unable to unmap buffer.
 */
errno_t buf_unmap_range(buf_t bp);

/*!
 *  @function buf_setdrvdata
 *  @abstract Set driver-specific data on a buffer.
 *  @param bp Buffer whose driver-data to set.
 *  @param drvdata Opaque driver data.
 */
void    buf_setdrvdata(buf_t bp, void *drvdata);

/*!
 *  @function buf_setdrvdata
 *  @abstract Get driver-specific data from a buffer.
 *  @param bp Buffer whose driver data to get.
 *  @return Opaque driver data.
 */
void *  buf_drvdata(buf_t bp);

/*!
 *  @function buf_setfsprivate
 *  @abstract Set filesystem-specific data on a buffer.
 *  @param bp Buffer whose filesystem data to set.
 *  @param fsprivate Opaque filesystem data.
 */
void    buf_setfsprivate(buf_t bp, void *fsprivate);

/*!
 *  @function buf_fsprivate
 *  @abstract Get filesystem-specific data from a buffer.
 *  @param bp Buffer whose filesystem data to get.
 *  @return Opaque filesystem data.
 */
void *  buf_fsprivate(buf_t bp);

/*!
 *  @function buf_blkno
 *  @abstract Get physical block number associated with a buffer, in the sense of VNOP_BLOCKMAP.
 *  @discussion When a buffer's physical block number is the same is its logical block number, then the physical
 *  block number is considered uninitialized.  A physical block number of -1 indicates that there is no valid
 *  physical mapping (e.g. the logical block is invalid or corresponds to a sparse region in a file).  Physical
 *  block number is normally set by the cluster layer or by buf_getblk().
 *  @param bp Buffer whose physical block number to get.
 *  @return Block number.
 */
daddr64_t buf_blkno(buf_t bp);

/*!
 *  @function buf_lblkno
 *  @abstract Get logical block number associated with a buffer.
 *  @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
 *  for example by buf_bread().
 *  @param bp Buffer whose logical block number to get.
 *  @return Block number.
 */
daddr64_t buf_lblkno(buf_t bp);

/*!
 *  @function buf_lblksize
 *  @abstract Get the block size used to calculate the logical block number associated with a buffer.
 *  @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
 *  for example by buf_bread(). Block size is the block size used to calculate the file offset.
 *  @param bp Buffer whose logical block size to get.
 *  @return Block size.
 */
uint32_t buf_lblksize(buf_t bp);

/*!
 *  @function buf_setblkno
 *  @abstract Set physical block number associated with a buffer.
 *  @discussion Physical block number is generally set by the cluster layer or by buf_getblk().
 *  @param bp Buffer whose physical block number to set.
 *  @param blkno Block number to set.
 */
void    buf_setblkno(buf_t bp, daddr64_t blkno);

/*!
 *  @function buf_setlblkno
 *  @abstract Set logical block number associated with a buffer.
 *  @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
 *  for example by buf_bread().
 *  @param bp Buffer whose logical block number to set.
 *  @param lblkno Block number to set.
 */
void    buf_setlblkno(buf_t bp, daddr64_t lblkno);

/*!
 *  @function buf_setlblksize
 *  @abstract Set block size used to set the logical block number associated with a buffer.
 *  @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
 *  for example by buf_bread().
 *  @param bp Buffer whose logical block size to set.
 *  @param lblksize Block size to set.
 */
void    buf_setlblksize(buf_t bp, uint32_t lblksize);

/*!
 *  @function buf_count
 *  @abstract Get count of valid bytes in a buffer.  This may be less than the space allocated to the buffer.
 *  @param bp Buffer whose byte count to get.
 *  @return Byte count.
 */
uint32_t buf_count(buf_t bp);

/*!
 *  @function buf_size
 *  @abstract Get size of data region allocated to a buffer.
 *  @discussion May be larger than amount of valid data in buffer.
 *  @param bp Buffer whose size to get.
 *  @return Size.
 */
uint32_t buf_size(buf_t bp);

/*!
 *  @function buf_resid
 *  @abstract Get a count of bytes which were not consumed by an I/O on a buffer.
 *  @discussion Set when an I/O operations completes.
 *  @param bp Buffer whose outstanding count to get.
 *  @return Count of unwritten/unread bytes.
 */
uint32_t buf_resid(buf_t bp);

/*!
 *  @function buf_setcount
 *  @abstract Set count of valid bytes in a buffer.  This may be less than the space allocated to the buffer.
 *  @param bp Buffer whose byte count to set.
 *  @param bcount Count to set.
 */
void    buf_setcount(buf_t bp, uint32_t bcount);

/*!
 *  @function buf_setsize
 *  @abstract Set size of data region allocated to a buffer.
 *  @discussion May be larger than amount of valid data in buffer.  Should be used by
 *  code which is manually providing storage for an iobuf, one allocated with buf_alloc().
 *  @param bp Buffer whose size to set.
 */
void    buf_setsize(buf_t bp, uint32_t);

/*!
 *  @function buf_setresid
 *  @abstract Set a count of bytes outstanding for I/O in a buffer.
 *  @discussion Set when an I/O operations completes.  Examples: called by IOStorageFamily when I/O
 *  completes, often called on an "original" buffer when using a manipulated buffer to perform I/O
 *  on behalf of the first.
 *  @param bp Buffer whose outstanding count to set.
 */
void    buf_setresid(buf_t bp, uint32_t resid);

/*!
 *  @function buf_setdataptr
 *  @abstract Set the address at which a buffer's data will be stored.
 *  @discussion In traditional buffer use, the data pointer will be set automatically. This routine is
 *  useful with iobufs (allocated with buf_alloc()).
 *  @param bp Buffer whose data pointer to set.
 *  @param data Pointer to data region.
 */
void    buf_setdataptr(buf_t bp, uintptr_t data);

/*!
 *  @function buf_dataptr
 *  @abstract Get the address at which a buffer's data is stored; for iobufs, this must
 *  be set with buf_setdataptr().  See buf_map().
 *  @param bp Buffer whose data pointer to retrieve.
 *  @return Data pointer; NULL if unset.
 */
uintptr_t buf_dataptr(buf_t bp);

/*!
 *  @function buf_vnode
 *  @abstract Get the vnode associated with a buffer.
 *  @discussion Every buffer is associated with a file.  Because there is an I/O in flight,
 *  there is an iocount on this vnode; it is returned WITHOUT an extra iocount, and vnode_put()
 *  need NOT be called.
 *  @param bp Buffer whose vnode to retrieve.
 *  @return Buffer's vnode.
 */
vnode_t buf_vnode(buf_t bp);

/*!
 *  @function buf_setvnode
 *  @abstract Set the vnode associated with a buffer.
 *  @discussion This call need not be used on traditional buffers; it is for use with iobufs.
 *  @param bp Buffer whose vnode to set.
 *  @param vp The vnode to attach to the buffer.
 */
void    buf_setvnode(buf_t bp, vnode_t vp);

/*!
 *  @function buf_device
 *  @abstract Get the device ID associated with a buffer.
 *  @discussion In traditional buffer use, this value is NODEV until buf_strategy() is called unless
 *  buf_getblk() was passed a device vnode.  It is set on an iobuf if buf_alloc() is passed a device
 *  vnode or if buf_setdevice() is called.
 *  @param bp Buffer whose device ID to retrieve.
 *  @return Device id.
 */
dev_t   buf_device(buf_t bp);

/*!
 *  @function buf_setdevice
 *  @abstract Set the device associated with a buffer.
 *  @discussion A buffer's device is set in buf_strategy() (or in buf_getblk() if the file is a device).
 *  It is also set on an iobuf if buf_alloc() is passed a device vnode.
 *  @param bp Buffer whose device ID to set.
 *  @param vp Device to set on the buffer.
 *  @return 0 for success, EINVAL if vp is not a device file.
 */
errno_t buf_setdevice(buf_t bp, vnode_t vp);

/*!
 *  @function buf_strategy
 *  @abstract Pass an I/O request for a buffer down to the device layer.
 *  @discussion This is one of the most important routines in the buffer cache layer.  For buffers obtained
 *  through buf_getblk, it handles finding physical block numbers for the I/O (with VNOP_BLKTOOFF and
 *  VNOP_BLOCKMAP), packaging the I/O into page-sized chunks, and initiating I/O on the disk by calling
 *  the device's strategy routine. If a buffer's UPL has been set manually with buf_setupl(), it assumes
 *  that the request is already correctly configured with a block number and a size divisible by page size
 *  and will just call directly to the device.
 *  @param devvp Device on which to perform I/O
 *  @param ap vnop_strategy_args structure (most importantly, a buffer).
 *  @return 0 for success, or errors from filesystem or device layers.
 */
errno_t buf_strategy(vnode_t devvp, void *ap);

/*
 * Flags for buf_invalblkno()
 */
#define BUF_WAIT        0x01

/*!
 *  @function buf_invalblkno
 *  @abstract Invalidate a filesystem logical block in a file.
 *  @discussion buf_invalblkno() tries to make the data for a given block in a file
 *  invalid; if the buffer for that block is found in core and is not busy, we mark it
 *  invalid and call buf_brelse() (see "flags" param for what happens if the buffer is busy).
 *  buf_brelse(), noticing that it is invalid, will
 *  will return the buffer to the empty-buffer list and tell the VM subsystem to abandon
 *  the relevant pages.  Data will not be written to backing store--it will be cast aside.
 *  Note that this function will only work if the block in question has been
 *  obtained with a buf_getblk().  If data has been read into core without using
 *  traditional buffer cache routines, buf_invalblkno() will not be able to invalidate it--this
 *  includes the use of iobufs.
 *  @param vp vnode whose block to invalidate.
 *  @param lblkno Logical block number.
 *  @param flags BUF_WAIT: wait for busy buffers to become unbusy and invalidate them then.  Otherwise,
 *  just return EBUSY for busy blocks.
 *  @return 0 for success, EINVAL if vp is not a device file.
 */
errno_t buf_invalblkno(vnode_t vp, daddr64_t lblkno, int flags);

/*!
 *  @function buf_callback
 *  @abstract Get the function set to be called when I/O on a buffer completes.
 *  @discussion A function returned by buf_callback was originally set with buf_setcallback().
 *  @param bp Buffer whose callback to get.
 *  @return 0 for success, or errors from filesystem or device layers.
 */
void * buf_callback(buf_t bp);

/*!
 *  @function buf_setcallback
 *  @abstract Set a function to be called once when I/O on a buffer completes.
 *  @discussion A one-shot callout set with buf_setcallback() will be called from buf_biodone()
 *  when I/O completes. It will be passed the "transaction" argument as well as the buffer.
 *  buf_setcallback() also marks the buffer as B_ASYNC.
 *  @param bp Buffer whose callback to set.
 *  @param callback function to use as callback.
 *  @param transaction Additional argument to callback function.
 *  @return 0; always succeeds.
 */
errno_t buf_setcallback(buf_t bp, void (*callback)(buf_t, void *), void *transaction);

/*!
 *  @function buf_setupl
 *  @abstract Set the UPL (Universal Page List), and offset therein, on a buffer.
 *  @discussion buf_setupl() should only be called on buffers allocated with buf_alloc().
 *  A subsequent call to buf_map() will map the UPL and give back the address at which data
 *  begins. After buf_setupl() is called, a buffer is marked B_CLUSTER; when this is the case,
 *  buf_strategy() assumes that a buffer is correctly configured to be passed to the device
 *  layer without modification. Passing a NULL upl will clear the upl and the B_CLUSTER flag on the
 *  buffer.
 *  @param bp Buffer whose upl to set.
 *  @param upl UPL to set in the buffer.
 *  @param offset Offset within upl at which relevant data begin.
 *  @return 0 for success, EINVAL if the buffer was not allocated with buf_alloc().
 */
errno_t buf_setupl(buf_t bp, upl_t upl, uint32_t offset);

/*!
 *  @function buf_clone
 *  @abstract Clone a buffer with a restricted range and an optional callback.
 *  @discussion Generates a buffer which is identical to its "bp" argument except that
 *  it spans a subset of the data of the original.  The buffer to be cloned should
 *  have been allocated with buf_alloc().  Checks its arguments to make sure
 *  that the data subset is coherent. Optionally, adds a callback function and argument to it
 *  to be called when I/O completes (as with buf_setcallback(), but B_ASYNC is not set).  If the original buffer had
 *  a upl set through buf_setupl(), this upl is copied to the new buffer; otherwise, the original's
 *  data pointer is used raw. The buffer must be released with buf_free().
 *  @param bp Buffer to clone.
 *  @param io_offset Offset, relative to start of data in original buffer, at which new buffer's data will begin.
 *  @param io_size Size of buffer region in new buffer, in the sense of buf_count().
 *  @param iodone Callback to be called from buf_biodone() when I/O completes, in the sense of buf_setcallback().
 *  @param arg Argument to pass to iodone() callback.
 *  @return NULL if io_offset/io_size combination is invalid for the buffer to be cloned; otherwise, the new buffer.
 */
buf_t   buf_clone(buf_t bp, int io_offset, int io_size, void (*iodone)(buf_t, void *), void *arg);


/*!
 *  @function buf_create_shadow
 *  @abstract Create a shadow buffer with optional private storage and an optional callback.
 *  @param bp Buffer to shadow.
 *  @param force_copy If TRUE, do not link the shadaow to 'bp' and if 'external_storage' == NULL,
 *  force a copy of the data associated with 'bp'.
 *  @param external_storage If non-NULL, associate it with the new buffer as its storage instead of the
 *  storage currently associated with 'bp'.
 *  @param iodone Callback to be called from buf_biodone() when I/O completes, in the sense of buf_setcallback().
 *  @param arg Argument to pass to iodone() callback.
 *  @return NULL if the buffer to be shadowed is not B_META or a primary buffer (i.e. not a shadow buffer); otherwise, the new buffer.
 */

buf_t   buf_create_shadow(buf_t bp, boolean_t force_copy, uintptr_t external_storage, void (*iodone)(buf_t, void *), void *arg);


/*!
 *  @function buf_shadow
 *  @abstract returns true if 'bp' is a shadow of another buffer.
 *  @param bp Buffer to query.
 *  @return 1 if 'bp' is a shadow, 0 otherwise.
 */
int     buf_shadow(buf_t bp);


/*!
 *  @function buf_alloc
 *  @abstract Allocate an uninitialized buffer.
 *  @discussion A buffer returned by buf_alloc() is marked as busy and as an iobuf; it has no storage set up and must be
 *  set up using buf_setdataptr() or buf_setupl()/buf_map().
 *  @param vp vnode to associate with the buffer: optionally NULL.  If vp is a device file, then
 *  the buffer's associated device will be set. If vp is NULL, it can be set later with buf_setvnode().
 *  @return New buffer.
 */
buf_t   buf_alloc(vnode_t vp);

/*!
 *  @function buf_free
 *  @abstract Free a buffer that was allocated with buf_alloc().
 *  @discussion The storage (UPL, data pointer) associated with an iobuf must be freed manually.
 *  @param bp The buffer to free.
 */
void    buf_free(buf_t bp);

/*
 * flags for buf_invalidateblks
 */
#define BUF_WRITE_DATA  0x0001          /* write data blocks first */
#define BUF_SKIP_META   0x0002          /* skip over metadata blocks */
#define BUF_INVALIDATE_LOCKED   0x0004  /* force B_LOCKED blocks to be invalidated */

/*!
 *  @function buf_invalidateblks
 *  @abstract Invalidate all the blocks associated with a vnode.
 *  @discussion This function does for all blocks associated with a vnode what buf_invalblkno does for one block.
 *  Again, it will only be able to invalidate data which were populated with traditional buffer cache routines,
 *  i.e. by buf_getblk() and callers thereof. Unlike buf_invalblkno(), it can be made to write dirty data to disk
 *  rather than casting it aside.
 *  @param vp The vnode whose data to invalidate.
 *  @param flags BUF_WRITE_DATA: write dirty data to disk with VNOP_BWRITE() before kicking buffer cache entries out.
 *  BUF_SKIP_META: do not invalidate metadata blocks.
 *  @param slpflag Flags to pass to "msleep" while waiting to acquire busy buffers.
 *  @param slptimeo Timeout in "hz" (1/100 second) to wait for a buffer to become unbusy before waking from sleep
 *  and re-starting the scan.
 *  @return 0 for success, error values from msleep().
 */
int     buf_invalidateblks(vnode_t vp, int flags, int slpflag, int slptimeo);

/*
 * flags for buf_flushdirtyblks and buf_iterate
 */
#define BUF_SKIP_NONLOCKED      0x01
#define BUF_SKIP_LOCKED         0x02
#define BUF_SCAN_CLEAN          0x04    /* scan the clean buffers */
#define BUF_SCAN_DIRTY          0x08    /* scan the dirty buffers */
#define BUF_NOTIFY_BUSY         0x10    /* notify the caller about the busy pages during the scan */


#define BUF_RETURNED            0
#define BUF_RETURNED_DONE       1
#define BUF_CLAIMED             2
#define BUF_CLAIMED_DONE        3
/*!
 *  @function buf_flushdirtyblks
 *  @abstract Write dirty file blocks to disk.
 *  @param vp The vnode whose blocks to flush.
 *  @param wait Wait for writes to complete before returning.
 *  @param flags Can pass zero, meaning "flush all dirty buffers."
 *  BUF_SKIP_NONLOCKED: Skip buffers which are not busy when we encounter them.
 *  BUF_SKIP_LOCKED: Skip buffers which are busy when we encounter them.
 *  @param msg String to pass to msleep().
 */
void    buf_flushdirtyblks(vnode_t vp, int wait, int flags, const char *msg);

/*!
 *  @function buf_iterate
 *  @abstract Perform some operation on all buffers associated with a vnode.
 *  @param vp The vnode whose buffers to scan.
 *  @param callout Function to call on each buffer.  Should return one of:
 *  BUF_RETURNED: buf_iterate() should call buf_brelse() on the buffer.
 *  BUF_RETURNED_DONE: buf_iterate() should call buf_brelse() on the buffer and then stop iterating.
 *  BUF_CLAIMED: buf_iterate() should continue iterating (and not call buf_brelse()).
 *  BUF_CLAIMED_DONE: buf_iterate() should stop iterating (and not call buf_brelse()).
 *  @param flags
 *  BUF_SKIP_NONLOCKED: Skip buffers which are not busy when we encounter them. BUF_SKIP_LOCKED: Skip buffers which are busy when we encounter them.
 *  BUF_SCAN_CLEAN: Call out on clean buffers.
 *  BUF_SCAN_DIRTY: Call out on dirty buffers.
 *  BUF_NOTIFY_BUSY: If a buffer cannot be acquired, pass a NULL buffer to callout; otherwise,
 *  that buffer will be silently skipped.
 *  @param arg Argument to pass to callout in addition to buffer.
 */
void    buf_iterate(vnode_t vp, int (*callout)(buf_t, void *), int flags, void *arg);

/*!
 *  @function buf_clear
 *  @abstract Zero out the storage associated with a buffer.
 *  @discussion Calls buf_map() to get the buffer's data address; for a B_CLUSTER
 *  buffer (one which has had buf_setupl() called on it), it tries to map the buffer's
 *  UPL into memory; should only be called once during the life cycle of an iobuf (one allocated
 *  with buf_alloc()).
 *  @param bp The buffer to zero out.
 */
void    buf_clear(buf_t bp);

/*!
 *  @function buf_bawrite
 *  @abstract Start an asychronous write on a buffer.
 *  @discussion Calls VNOP_BWRITE to start the process of propagating an asynchronous write down to the device layer.
 *  Callers can wait for writes to complete at their discretion using buf_biowait().  When this function is called,
 *  data should already have been written to the buffer's data region.
 *  @param bp The buffer on which to initiate I/O.
 *  @return EWOULDBLOCK if write count is high and "throttle" is zero; otherwise, errors from VNOP_BWRITE.
 */
errno_t buf_bawrite(buf_t bp);

/*!
 *  @function buf_bdwrite
 *  @abstract Mark a buffer for delayed write.
 *  @discussion Marks a buffer as waiting for delayed write and the current I/O as complete; data will be written to backing store
 *  before the buffer is reused, but it will not be queued for I/O immediately.  Note that for buffers allocated
 *  with buf_alloc(), there are no such guarantees; you must take care of your own flushing to disk.  If
 *  the number of delayed writes pending on the system is greater than an internal limit and the caller has not
 *  requested otherwise [see return_error] , buf_bdwrite() will unilaterally launch an asynchronous I/O with buf_bawrite() to keep the pile of
 *  delayed writes from getting too large.
 *  @param bp The buffer to mark for delayed write.
 *  @return EAGAIN for return_error != 0 case, 0 for succeess, errors from buf_bawrite.
 */
errno_t buf_bdwrite(buf_t bp);

/*!
 *  @function buf_bwrite
 *  @abstract Write a buffer's data to backing store.
 *  @discussion Once the data in a buffer has been modified, buf_bwrite() starts sending it to disk by calling
 *  VNOP_STRATEGY.  Unless B_ASYNC has been set on the buffer (by buf_setflags() or otherwise), data will have
 *  been written to disk when buf_bwrite() returns.  See Bach (p 56).
 *  @param bp The buffer to write to disk.
 *  @return 0 for success; errors from buf_biowait().
 */
errno_t buf_bwrite(buf_t bp);

/*!
 *  @function buf_biodone
 *  @abstract Mark an I/O as completed.
 *  @discussion buf_biodone() should be called by whosoever decides that an I/O on a buffer is complete; for example,
 *  IOStorageFamily.  It clears the dirty flag on a buffer and signals on the vnode that a write has completed
 *  with vnode_writedone(). If a callout or filter has been set on the buffer, that function is called.  In the case
 *  of a callout, that function is expected to take care of cleaning up and freeing the buffer.
 *  Otherwise, if the buffer is marked B_ASYNC (e.g. it was passed to buf_bawrite()), then buf_biodone()
 *  considers itself justified in calling buf_brelse() to return it to free lists--no one is waiting for it.  Finally,
 *  waiters on the bp (e.g. in buf_biowait()) are woken up.
 *  @param bp The buffer to mark as done with I/O.
 */
void    buf_biodone(buf_t bp);

/*!
 *  @function buf_biowait
 *  @abstract Wait for I/O on a buffer to complete.
 *  @discussion Waits for I/O on a buffer to finish, as marked by a buf_biodone() call.
 *  @param bp The buffer to wait on.
 *  @return 0 for a successful wait; nonzero the buffer has been marked as EINTR or had an error set on it.
 */
errno_t buf_biowait(buf_t bp);

/*!
 *  @function buf_brelse
 *  @abstract Release any claim to a buffer, sending it back to free lists.
 *  @discussion buf_brelse() cleans up buffer state and releases a buffer to the free lists.  If the buffer
 *  is not marked invalid and its pages are dirty (e.g. a delayed write was made), its data will be commited
 *  to backing store. If it is marked invalid, its data will be discarded completely.
 *  A valid, cacheable buffer will be put on a list and kept in the buffer hash so it
 *  can be found again; otherwise, it will be dissociated from its vnode and treated as empty.  Which list a valid
 *  buffer is placed on depends on the use of buf_markaged(), whether it is metadata, and the B_LOCKED flag.  A
 *  B_LOCKED buffer will not be available for reuse by other files, though its data may be paged out.
 *  Note that buf_brelse() is intended for use with traditionally allocated buffers.
 *  @param bp The buffer to release.
 */
void    buf_brelse(buf_t bp);

/*!
 *  @function buf_bread
 *  @abstract Synchronously read a block of a file.
 *  @discussion buf_bread() is the traditional way to read a single logical block of a file through the buffer cache.
 *  It tries to find the buffer and corresponding page(s) in core, calls VNOP_STRATEGY if necessary to bring the data
 *  into memory, and waits for I/O to complete.  It should not be used to read blocks of greater than 4K (one VM page)
 *  in size; use cluster routines for large reads.  Indeed, the cluster layer is a more efficient choice for reading DATA
 *  unless you need some finely-tuned semantics that it cannot provide.
 *  @param vp The file from which to read.
 *  @param blkno The logical (filesystem) block number to read.
 *  @param size Size of block; do not use for sizes > 4K.
 *  @param cred Credential to store and use for reading from disk if data are not already in core.
 *  @param bpp Destination pointer for buffer.
 *  @return 0 for success, or an error from buf_biowait().
 */
errno_t buf_bread(vnode_t vp, daddr64_t blkno, int size, kauth_cred_t cred, buf_t *bpp);

/*!
 *  @function buf_breadn
 *  @abstract Read a block from a file with read-ahead.
 *  @discussion buf_breadn() reads one block synchronously in the style of buf_bread() and fires
 *  off a specified set of asynchronous reads to improve the likelihood of future cache hits.
 *  It should not be used to read blocks of greater than 4K (one VM page) in size; use cluster
 *  routines for large reads.  Indeed, the cluster layer is a more efficient choice for reading DATA
 *  unless you need some finely-tuned semantics that it cannot provide.
 *  @param vp The file from which to read.
 *  @param blkno The logical (filesystem) block number to read synchronously.
 *  @param size Size of block; do not use for sizes > 4K.
 *  @param rablks Array of logical block numbers for asynchronous read-aheads.
 *  @param rasizes Array of block sizes for asynchronous read-aheads, each index corresponding to same index in "rablks."
 *  @param nrablks Number of entries in read-ahead arrays.
 *  @param cred Credential to store and use for reading from disk if data are not already in core.
 *  @param bpp Destination pointer for buffer.
 *  @return 0 for success, or an error from buf_biowait().
 */
errno_t buf_breadn(vnode_t vp, daddr64_t blkno, int size, daddr64_t *rablks, int *rasizes, int nrablks, kauth_cred_t cred, buf_t *bpp);

/*!
 *  @function buf_meta_bread
 *  @abstract Synchronously read a metadata block of a file.
 *  @discussion buf_meta_bread() is the traditional way to read a single logical block of a file through the buffer cache.
 *  It tries to find the buffer and corresponding page(s) in core, calls VNOP_STRATEGY if necessary to bring the data
 *  into memory, and waits for I/O to complete.  It should not be used to read blocks of greater than 4K (one VM page)
 *  in size; use cluster routines for large reads.  Reading meta-data through the traditional buffer cache, unlike
 *  reading data, is efficient and encouraged, especially if the blocks being read are significantly smaller than page size.
 *  @param vp The file from which to read.
 *  @param blkno The logical (filesystem) block number to read.
 *  @param size Size of block; do not use for sizes > 4K.
 *  @param cred Credential to store and use for reading from disk if data are not already in core.
 *  @param bpp Destination pointer for buffer.
 *  @return 0 for success, or an error from buf_biowait().
 */
errno_t buf_meta_bread(vnode_t vp, daddr64_t blkno, int size, kauth_cred_t cred, buf_t *bpp);

/*!
 *  @function buf_meta_breadn
 *  @abstract Read a metadata block from a file with read-ahead.
 *  @discussion buf_meta_breadn() reads one block synchronously in the style of buf_meta_bread() and fires
 *  off a specified set of asynchronous reads to improve the likelihood of future cache hits.
 *  It should not be used to read blocks of greater than 4K (one VM page) in size; use cluster
 *  routines for large reads.
 *  @param vp The file from which to read.
 *  @param blkno The logical (filesystem) block number to read synchronously.
 *  @param size Size of block; do not use for sizes > 4K.
 *  @param rablks Array of logical block numbers for asynchronous read-aheads.
 *  @param rasizes Array of block sizes for asynchronous read-aheads, each index corresponding to same index in "rablks."
 *  @param nrablks Number of entries in read-ahead arrays.
 *  @param cred Credential to store and use for reading from disk if data are not already in core.
 *  @param bpp Destination pointer for buffer.
 *  @return 0 for success, or an error from buf_biowait().
 */
errno_t buf_meta_breadn(vnode_t vp, daddr64_t blkno, int size, daddr64_t *rablks, int *rasizes, int nrablks, kauth_cred_t cred, buf_t *bpp);

/*!
 *  @function minphys
 *  @abstract Adjust a buffer's count to be no more than maximum physical I/O transfer size for the host architecture.
 *  @discussion physio() takes as a parameter a function to bound transfer sizes for each VNOP_STRATEGY() call.  minphys()
 *  is a default implementation.  It calls buf_setcount() to make the buffer's count the min() of its current count
 *  and the max I/O size for the host architecture.
 *  @param bp The buffer whose byte count to modify.
 *  @return New byte count.
 */
u_int   minphys(buf_t bp);

/*!
 *  @function physio
 *  @abstract Perform I/O on a device to/from target memory described by a uio.
 *  @discussion physio() allows I/O directly from a device to user-space memory.  It waits
 *  for all I/O to complete before returning.
 *  @param f_strategy Strategy routine to call to initiate I/O.
 *  @param bp Buffer to configure and pass to strategy routine; can be NULL.
 *  @param dev Device on which to perform I/O.
 *  @param flags B_READ or B_WRITE.
 *  @param f_minphys Function which calls buf_setcount() to set a byte count which is suitably
 *  small for the device in question.  Returns byte count that has been set (or unchanged) on the buffer.
 *  @param uio UIO describing the I/O operation.
 *  @param blocksize Logical block size for this vnode.
 *  @return 0 for success; EFAULT for an invalid uio; errors from buf_biowait().
 */
int     physio(void (*f_strategy)(buf_t), buf_t bp, dev_t dev, int flags, u_int (*f_minphys)(buf_t), struct uio *uio, int blocksize);


/*
 * Flags for operation type in getblk()
 */
#define BLK_READ        0x01    /* buffer for read */
#define BLK_WRITE       0x02    /* buffer for write */
#define BLK_META        0x10    /* buffer for metadata */
/*
 * modifier for above flags...  if set, getblk will only return
 * a bp that is already valid... i.e. found in the cache
 */
#define BLK_ONLYVALID   0x80000000

/*!
 *  @function buf_getblk
 *  @abstract Traditional buffer cache routine to get a buffer corresponding to a logical block in a file.
 *  @discussion buf_getblk() gets a buffer, not necessarily containing valid data, representing a block in a file.
 *  A metadata buffer will be returned with its own zone-allocated storage, managed by the traditional buffer-cache
 *  layer, whereas data buffers will be returned hooked into backing by the UBC (which in fact controls the caching of data).
 *  buf_getblk() first looks for the buffer header in cache; if the buffer is in-core but busy, buf_getblk() will wait for it to become
 *  unbusy, depending on the slpflag and slptimeo parameters. If the buffer is found unbusy and is a metadata buffer,
 *  it must already contain valid data and will be returned directly; data buffers will have a UPL configured to
 *  prepare for interaction with the underlying UBC.  If the buffer is found in core, it will be marked as such
 *  and buf_fromcache() will return truth. A buffer is allocated and initialized (but not filled with data)
 *  if none is found in core. buf_bread(), buf_breadn(), buf_meta_bread(), and buf_meta_breadn() all
 *  return buffers obtained with buf_getblk().
 *  @param vp File for which to get block.
 *  @param blkno Logical block number.
 *  @param size Size of block.
 *  @param slpflag Flag to pass to msleep() while waiting for buffer to become unbusy.
 *  @param slptimeo Time, in milliseconds, to wait for buffer to become unbusy.  0 means to wait indefinitely.
 *  @param operation BLK_READ: want a read buffer.  BLK_WRITE: want a write buffer.  BLK_META: want a metadata buffer.  BLK_ONLYVALID:
 *  only return buffers which are found in core (do not allocate anew), and do not change buffer size.  The last remark means
 *  that if a given logical block is found in core with a different size than what is requested, the buffer size will not be modified.
 *  @return Buffer found in core or newly allocated, either containing valid data or ready for I/O.
 */
buf_t   buf_getblk(vnode_t vp, daddr64_t blkno, int size, int slpflag, int slptimeo, int operation);

/*!
 *  @function buf_geteblk
 *  @abstract Get a metadata buffer which is marked invalid and not associated with any vnode.
 *  @discussion A buffer is returned with zone-allocated storage of the specified size, marked B_META and invalid.
 *  It has no vnode and is not visible in the buffer hash.
 *  @param size Size of buffer.
 *  @return Always returns a new buffer.
 */
buf_t   buf_geteblk(int size);

/*!
 *  @function buf_clear_redundancy_flags
 *  @abstract Clear flags on a buffer.
 *  @discussion buffer_redundancy_flags &= ~flags
 *  @param bp Buffer whose flags to clear.
 *  @param flags Flags to remove from buffer's mask
 */
void    buf_clear_redundancy_flags(buf_t bp, uint32_t flags);

/*!
 *  @function buf_redundancyflags
 *  @abstract Get redundancy flags set on a buffer.
 *  @param bp Buffer whose redundancy flags to grab.
 *  @return flags.
 */
uint32_t        buf_redundancy_flags(buf_t bp);

/*!
 *  @function buf_setredundancyflags
 *  @abstract Set redundancy flags on a buffer.
 *  @discussion buffer_redundancy_flags |= flags
 *  @param bp Buffer whose flags to set.
 *  @param flags Flags to add to buffer's redundancy flags
 */
void    buf_set_redundancy_flags(buf_t bp, uint32_t flags);

/*!
 *  @function buf_attr
 *  @abstract Gets the attributes for this buf.
 *  @param bp Buffer whose attributes to get.
 *  @return bufattr_t.
 */
bufattr_t buf_attr(buf_t bp);

/*!
 *  @function buf_markstatic
 *  @abstract Mark a buffer as being likely to contain static data.
 *  @param bp Buffer to mark.
 */
void buf_markstatic(buf_t bp);

/*!
 *  @function buf_static
 *  @abstract Check if a buffer contains static data.
 *  @param bp Buffer to test.
 *  @return Nonzero if buffer has static data, 0 otherwise.
 */
int     buf_static(buf_t bp);

__options_decl(vnode_verify_kind_t, uint32_t, {
	VK_HASH_NONE = 0x00,
	VK_HASH_SHA3_256 = 0x01,
	VK_HASH_SHA3_384 = 0x02,
	VK_HASH_SHA3_512 = 0x03,
});

#define NUM_VERIFY_KIND 4

/*!
 *  @function buf_verify_enable
 *  @abstract Set up buf to retrieve hashes alongwith data.
 *  @param bp buf pointer.
 *  @param verify_kind specific algorithm to be used for the hash calculation.
 *  @return 0 if successful, error otherwise.
 */
errno_t buf_verify_enable(buf_t bp, vnode_verify_kind_t verify_kind);

/*!
 *  @function buf_verifyptr
 *  @abstract Gets pointer to the buffer to store the hash calculated for the data.
 *  @param bp buf pointer.
 *  @param len pointer to uint32_t variable to store the length.
 *  @return Pointer to a buffer (of length passed in second argument), NULL if there is no hash needed.
 */
uint8_t * buf_verifyptr(buf_t bp, uint32_t *len);

/*!
 *  @function bufattr_markiosched
 *  @abstract Mark a buffer as belonging to an io scheduled mount point
 *  @param bap Buffer attributes to mark.
 *  @discussion Marks the buffer so that spec_strategy() will know that it belongs to an io scheduled mount point
 */
void bufattr_markioscheduled(bufattr_t bap);

/*!
 *  @function bufattr_iosched
 *  @abstract Check if a buffer is marked as io scheduled
 *  @param bap Buffer attributes to test.
 *  @return Nonzero if the buffer is marked io scheduled, 0 otherwise.
 */
int bufattr_ioscheduled(bufattr_t bap);

/*!
 *  @function bufattr_markexpeditedmeta
 *  @abstract Mark a metadata I/O buffer as expedited (i.e. requires a high I/O tier).
 *  @param bap Buffer attributes to mark.
 *  @discussion Marks the buffer so that spec_strategy() will know that it should be expedited
 */
void bufattr_markexpeditedmeta(bufattr_t bap);

/*!
 *  @function bufattr_expeditedmeta
 *  @abstract Check if a buffer is marked as expedited metadata I/O.
 *  @param bap Buffer attributes to test.
 *  @return Nonzero if the buffer is marked expedited metadata I/O, 0 otherwise.
 */
int bufattr_expeditedmeta(bufattr_t bap);


__END_DECLS


/* Macros to clear/set/test flags. */
#define SET(t, f)       (t) |= (f)
#define CLR(t, f)       (t) &= ~(f)
#define ISSET(t, f)     ((t) & (f))


#endif /* !_SYS_BUF_H_ */
