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2de203163d
freebsd/include/sys/arc.h
Brian Atkinson a10e552b99
Adding Direct IO Support 
Adding O_DIRECT support to ZFS to bypass the ARC for writes/reads.

O_DIRECT support in ZFS will always ensure there is coherency between
buffered and O_DIRECT IO requests. This ensures that all IO requests,
whether buffered or direct, will see the same file contents at all
times. Just as in other FS's , O_DIRECT does not imply O_SYNC. While
data is written directly to VDEV disks, metadata will not be synced
until the associated  TXG is synced.
For both O_DIRECT read and write request the offset and request sizes,
at a minimum, must be PAGE_SIZE aligned. In the event they are not,
then EINVAL is returned unless the direct property is set to always (see
below).

For O_DIRECT writes:
The request also must be block aligned (recordsize) or the write
request will take the normal (buffered) write path. In the event that
request is block aligned and a cached copy of the buffer in the ARC,
then it will be discarded from the ARC forcing all further reads to
retrieve the data from disk.

For O_DIRECT reads:
The only alignment restrictions are PAGE_SIZE alignment. In the event
that the requested data is in buffered (in the ARC) it will just be
copied from the ARC into the user buffer.

For both O_DIRECT writes and reads the O_DIRECT flag will be ignored in
the event that file contents are mmap'ed. In this case, all requests
that are at least PAGE_SIZE aligned will just fall back to the buffered
paths. If the request however is not PAGE_SIZE aligned, EINVAL will
be returned as always regardless if the file's contents are mmap'ed.

Since O_DIRECT writes go through the normal ZIO pipeline, the
following operations are supported just as with normal buffered writes:
Checksum
Compression
Encryption
Erasure Coding
There is one caveat for the data integrity of O_DIRECT writes that is
distinct for each of the OS's supported by ZFS.
FreeBSD - FreeBSD is able to place user pages under write protection so
          any data in the user buffers and written directly down to the
	  VDEV disks is guaranteed to not change. There is no concern
	  with data integrity and O_DIRECT writes.
Linux - Linux is not able to place anonymous user pages under write
        protection. Because of this, if the user decides to manipulate
	the page contents while the write operation is occurring, data
	integrity can not be guaranteed. However, there is a module
	parameter `zfs_vdev_direct_write_verify` that controls the
	if a O_DIRECT writes that can occur to a top-level VDEV before
	a checksum verify is run before the contents of the I/O buffer
        are committed to disk. In the event of a checksum verification
	failure the write will return EIO. The number of O_DIRECT write
	checksum verification errors can be observed by doing
	`zpool status -d`, which will list all verification errors that
	have occurred on a top-level VDEV. Along with `zpool status`, a
	ZED event will be issues as `dio_verify` when a checksum
	verification error occurs.

ZVOLs and dedup is not currently supported with Direct I/O.

A new dataset property `direct` has been added with the following 3
allowable values:
disabled - Accepts O_DIRECT flag, but silently ignores it and treats
	   the request as a buffered IO request.
standard - Follows the alignment restrictions  outlined above for
	   write/read IO requests when the O_DIRECT flag is used.
always   - Treats every write/read IO request as though it passed
           O_DIRECT and will do O_DIRECT if the alignment restrictions
	   are met otherwise will redirect through the ARC. This
	   property will not allow a request to fail.

There is also a module parameter zfs_dio_enabled that can be used to
force all reads and writes through the ARC. By setting this module
parameter to 0, it mimics as if the  direct dataset property is set to
disabled.

Reviewed-by: Brian Behlendorf <behlendorf@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Co-authored-by: Mark Maybee <mark.maybee@delphix.com>
Co-authored-by: Matt Macy <mmacy@FreeBSD.org>
Co-authored-by: Brian Behlendorf <behlendorf@llnl.gov>
Closes #10018
2024-09-14 13:47:59 -07:00

360 lines
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or https://opensource.org/licenses/CDDL-1.0.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2016 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
* Copyright (c) 2019, Allan Jude
* Copyright (c) 2019, Klara Inc.
*/
#ifndef _SYS_ARC_H
#define _SYS_ARC_H
#include <sys/zfs_context.h>
#ifdef __cplusplus
extern "C" {
#endif
#include <sys/zio.h>
#include <sys/dmu.h>
#include <sys/spa.h>
#include <sys/zfs_refcount.h>
/*
* Used by arc_flush() to inform arc_evict_state() that it should evict
* all available buffers from the arc state being passed in.
*/
#define ARC_EVICT_ALL UINT64_MAX
/*
* ZFS gets very unhappy when the maximum ARC size is smaller than the maximum
* block size and a larger block is written. To leave some safety margin, we
* limit the minimum for zfs_arc_max to the maximium transaction size.
*/
#define MIN_ARC_MAX DMU_MAX_ACCESS
#define HDR_SET_LSIZE(hdr, x) do { \
ASSERT(IS_P2ALIGNED(x, 1U << SPA_MINBLOCKSHIFT)); \
(hdr)->b_lsize = ((x) >> SPA_MINBLOCKSHIFT); \
} while (0)
#define HDR_SET_PSIZE(hdr, x) do { \
ASSERT(IS_P2ALIGNED((x), 1U << SPA_MINBLOCKSHIFT)); \
(hdr)->b_psize = ((x) >> SPA_MINBLOCKSHIFT); \
} while (0)
#define HDR_GET_LSIZE(hdr) ((hdr)->b_lsize << SPA_MINBLOCKSHIFT)
#define HDR_GET_PSIZE(hdr) ((hdr)->b_psize << SPA_MINBLOCKSHIFT)
typedef struct arc_buf_hdr arc_buf_hdr_t;
typedef struct arc_buf arc_buf_t;
typedef struct arc_prune arc_prune_t;
/*
* Because the ARC can store encrypted data, errors (not due to bugs) may arise
* while transforming data into its desired format - specifically, when
* decrypting, the key may not be present, or the HMAC may not be correct
* which signifies deliberate tampering with the on-disk state
* (assuming that the checksum was correct). If any error occurs, the "buf"
* parameter will be NULL.
*/
typedef void arc_read_done_func_t(zio_t *zio, const zbookmark_phys_t *zb,
const blkptr_t *bp, arc_buf_t *buf, void *priv);
typedef void arc_write_done_func_t(zio_t *zio, arc_buf_t *buf, void *priv);
typedef void arc_prune_func_t(uint64_t bytes, void *priv);
/* Shared module parameters */
extern uint_t zfs_arc_average_blocksize;
extern int l2arc_exclude_special;
/* generic arc_done_func_t's which you can use */
arc_read_done_func_t arc_bcopy_func;
arc_read_done_func_t arc_getbuf_func;
/* generic arc_prune_func_t wrapper for callbacks */
struct arc_prune {
arc_prune_func_t *p_pfunc;
void *p_private;
uint64_t p_adjust;
list_node_t p_node;
zfs_refcount_t p_refcnt;
};
typedef enum arc_strategy {
ARC_STRATEGY_META_ONLY = 0, /* Evict only meta data buffers */
ARC_STRATEGY_META_BALANCED = 1, /* Evict data buffers if needed */
} arc_strategy_t;
typedef enum arc_flags
{
/*
* Public flags that can be passed into the ARC by external consumers.
*/
ARC_FLAG_WAIT = 1 << 0, /* perform sync I/O */
ARC_FLAG_NOWAIT = 1 << 1, /* perform async I/O */
ARC_FLAG_PREFETCH = 1 << 2, /* I/O is a prefetch */
ARC_FLAG_CACHED = 1 << 3, /* I/O was in cache */
ARC_FLAG_L2CACHE = 1 << 4, /* cache in L2ARC */
ARC_FLAG_UNCACHED = 1 << 5, /* evict after use */
ARC_FLAG_PRESCIENT_PREFETCH = 1 << 6, /* long min lifespan */
/*
* Private ARC flags. These flags are private ARC only flags that
* will show up in b_flags in the arc_buf_hdr_t. These flags should
* only be set by ARC code.
*/
ARC_FLAG_IN_HASH_TABLE = 1 << 7, /* buffer is hashed */
ARC_FLAG_IO_IN_PROGRESS = 1 << 8, /* I/O in progress */
ARC_FLAG_IO_ERROR = 1 << 9, /* I/O failed for buf */
ARC_FLAG_INDIRECT = 1 << 10, /* indirect block */
/* Indicates that block was read with ASYNC priority. */
ARC_FLAG_PRIO_ASYNC_READ = 1 << 11,
ARC_FLAG_L2_WRITING = 1 << 12, /* write in progress */
ARC_FLAG_L2_EVICTED = 1 << 13, /* evicted during I/O */
ARC_FLAG_L2_WRITE_HEAD = 1 << 14, /* head of write list */
/*
* Encrypted or authenticated on disk (may be plaintext in memory).
* This header has b_crypt_hdr allocated. Does not include indirect
* blocks with checksums of MACs which will also have their X
* (encrypted) bit set in the bp.
*/
ARC_FLAG_PROTECTED = 1 << 15,
/* data has not been authenticated yet */
ARC_FLAG_NOAUTH = 1 << 16,
/* indicates that the buffer contains metadata (otherwise, data) */
ARC_FLAG_BUFC_METADATA = 1 << 17,
/* Flags specifying whether optional hdr struct fields are defined */
ARC_FLAG_HAS_L1HDR = 1 << 18,
ARC_FLAG_HAS_L2HDR = 1 << 19,
/*
* Indicates the arc_buf_hdr_t's b_pdata matches the on-disk data.
* This allows the l2arc to use the blkptr's checksum to verify
* the data without having to store the checksum in the hdr.
*/
ARC_FLAG_COMPRESSED_ARC = 1 << 20,
ARC_FLAG_SHARED_DATA = 1 << 21,
/*
* Fail this arc_read() (with ENOENT) if the data is not already present
* in cache.
*/
ARC_FLAG_CACHED_ONLY = 1 << 22,
/*
* Don't instantiate an arc_buf_t for arc_read_done.
*/
ARC_FLAG_NO_BUF = 1 << 23,
/*
* The arc buffer's compression mode is stored in the top 7 bits of the
* flags field, so these dummy flags are included so that MDB can
* interpret the enum properly.
*/
ARC_FLAG_COMPRESS_0 = 1 << 24,
ARC_FLAG_COMPRESS_1 = 1 << 25,
ARC_FLAG_COMPRESS_2 = 1 << 26,
ARC_FLAG_COMPRESS_3 = 1 << 27,
ARC_FLAG_COMPRESS_4 = 1 << 28,
ARC_FLAG_COMPRESS_5 = 1 << 29,
ARC_FLAG_COMPRESS_6 = 1 << 30
} arc_flags_t;
typedef enum arc_buf_flags {
ARC_BUF_FLAG_SHARED = 1 << 0,
ARC_BUF_FLAG_COMPRESSED = 1 << 1,
/*
* indicates whether this arc_buf_t is encrypted, regardless of
* state on-disk
*/
ARC_BUF_FLAG_ENCRYPTED = 1 << 2
} arc_buf_flags_t;
struct arc_buf {
arc_buf_hdr_t *b_hdr;
arc_buf_t *b_next;
void *b_data;
arc_buf_flags_t b_flags;
};
typedef enum arc_buf_contents {
ARC_BUFC_DATA, /* buffer contains data */
ARC_BUFC_METADATA, /* buffer contains metadata */
ARC_BUFC_NUMTYPES
} arc_buf_contents_t;
/*
* The following breakdowns of arc_size exist for kstat only.
*/
typedef enum arc_space_type {
ARC_SPACE_DATA,
ARC_SPACE_META,
ARC_SPACE_HDRS,
ARC_SPACE_L2HDRS,
ARC_SPACE_DBUF,
ARC_SPACE_DNODE,
ARC_SPACE_BONUS,
ARC_SPACE_ABD_CHUNK_WASTE,
ARC_SPACE_NUMTYPES
} arc_space_type_t;
typedef enum arc_state_type {
ARC_STATE_ANON,
ARC_STATE_MRU,
ARC_STATE_MRU_GHOST,
ARC_STATE_MFU,
ARC_STATE_MFU_GHOST,
ARC_STATE_L2C_ONLY,
ARC_STATE_UNCACHED,
ARC_STATE_NUMTYPES
} arc_state_type_t;
typedef struct arc_buf_info {
arc_state_type_t abi_state_type;
arc_buf_contents_t abi_state_contents;
uint32_t abi_flags;
uint32_t abi_bufcnt;
uint64_t abi_size;
uint64_t abi_spa;
uint64_t abi_access;
uint32_t abi_mru_hits;
uint32_t abi_mru_ghost_hits;
uint32_t abi_mfu_hits;
uint32_t abi_mfu_ghost_hits;
uint32_t abi_l2arc_hits;
uint32_t abi_holds;
uint64_t abi_l2arc_dattr;
uint64_t abi_l2arc_asize;
enum zio_compress abi_l2arc_compress;
} arc_buf_info_t;
/*
* Flags returned by arc_cached; describes which part of the arc
* the block is cached in.
*/
#define ARC_CACHED_EMBEDDED (1U << 0)
#define ARC_CACHED_IN_L1 (1U << 1)
#define ARC_CACHED_IN_MRU (1U << 2)
#define ARC_CACHED_IN_MFU (1U << 3)
#define ARC_CACHED_IN_L2 (1U << 4)
void arc_space_consume(uint64_t space, arc_space_type_t type);
void arc_space_return(uint64_t space, arc_space_type_t type);
boolean_t arc_is_metadata(arc_buf_t *buf);
boolean_t arc_is_encrypted(arc_buf_t *buf);
boolean_t arc_is_unauthenticated(arc_buf_t *buf);
enum zio_compress arc_get_compression(arc_buf_t *buf);
void arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt,
uint8_t *iv, uint8_t *mac);
int arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
boolean_t in_place);
void arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder,
dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv,
const uint8_t *mac);
arc_buf_t *arc_alloc_buf(spa_t *spa, const void *tag, arc_buf_contents_t type,
int32_t size);
arc_buf_t *arc_alloc_compressed_buf(spa_t *spa, const void *tag,
uint64_t psize, uint64_t lsize, enum zio_compress compression_type,
uint8_t complevel);
arc_buf_t *arc_alloc_raw_buf(spa_t *spa, const void *tag, uint64_t dsobj,
boolean_t byteorder, const uint8_t *salt, const uint8_t *iv,
const uint8_t *mac, dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel);
uint8_t arc_get_complevel(arc_buf_t *buf);
arc_buf_t *arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size);
arc_buf_t *arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel);
arc_buf_t *arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder,
const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel);
void arc_return_buf(arc_buf_t *buf, const void *tag);
void arc_loan_inuse_buf(arc_buf_t *buf, const void *tag);
void arc_buf_destroy(arc_buf_t *buf, const void *tag);
void arc_buf_info(arc_buf_t *buf, arc_buf_info_t *abi, int state_index);
uint64_t arc_buf_size(arc_buf_t *buf);
uint64_t arc_buf_lsize(arc_buf_t *buf);
void arc_buf_access(arc_buf_t *buf);
void arc_release(arc_buf_t *buf, const void *tag);
int arc_released(arc_buf_t *buf);
void arc_buf_sigsegv(int sig, siginfo_t *si, void *unused);
void arc_buf_freeze(arc_buf_t *buf);
void arc_buf_thaw(arc_buf_t *buf);
#ifdef ZFS_DEBUG
int arc_referenced(arc_buf_t *buf);
#else
#define arc_referenced(buf) ((void) sizeof (buf), 0)
#endif
int arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
arc_read_done_func_t *done, void *priv, zio_priority_t priority,
int flags, arc_flags_t *arc_flags, const zbookmark_phys_t *zb);
zio_t *arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
arc_buf_t *buf, boolean_t uncached, boolean_t l2arc, const zio_prop_t *zp,
arc_write_done_func_t *ready, arc_write_done_func_t *child_ready,
arc_write_done_func_t *done, void *priv, zio_priority_t priority,
int zio_flags, const zbookmark_phys_t *zb);
arc_prune_t *arc_add_prune_callback(arc_prune_func_t *func, void *priv);
void arc_remove_prune_callback(arc_prune_t *p);
void arc_freed(spa_t *spa, const blkptr_t *bp);
int arc_cached(spa_t *spa, const blkptr_t *bp);
void arc_flush(spa_t *spa, boolean_t retry);
void arc_tempreserve_clear(uint64_t reserve);
int arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg);
uint64_t arc_all_memory(void);
uint64_t arc_default_max(uint64_t min, uint64_t allmem);
uint64_t arc_target_bytes(void);
void arc_set_limits(uint64_t);
void arc_init(void);
void arc_fini(void);
/*
* Level 2 ARC
*/
void l2arc_add_vdev(spa_t *spa, vdev_t *vd);
void l2arc_remove_vdev(vdev_t *vd);
boolean_t l2arc_vdev_present(vdev_t *vd);
void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen);
boolean_t l2arc_range_check_overlap(uint64_t bottom, uint64_t top,
uint64_t check);
void l2arc_init(void);
void l2arc_fini(void);
void l2arc_start(void);
void l2arc_stop(void);
void l2arc_spa_rebuild_start(spa_t *spa);
#ifndef _KERNEL
extern boolean_t arc_watch;
#endif
#ifdef __cplusplus
}
#endif
#endif /* _SYS_ARC_H */
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