lvm2/lib/device/device.h

/*
 * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.  
 * Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
 *
 * This file is part of LVM2.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef _LVM_DEVICE_H
#define _LVM_DEVICE_H

#include "uuid.h"

#include <fcntl.h>

#define DEV_ACCESSED_W		0x00000001	/* Device written to? */
#define DEV_REGULAR		0x00000002	/* Regular file? */
#define DEV_ALLOCED		0x00000004	/* dm_malloc used */
#define DEV_OPENED_RW		0x00000008	/* Opened RW */
#define DEV_OPENED_EXCL		0x00000010	/* Opened EXCL */
#define DEV_O_DIRECT		0x00000020	/* Use O_DIRECT */
#define DEV_O_DIRECT_TESTED	0x00000040	/* DEV_O_DIRECT is reliable */
#define DEV_OPEN_FAILURE	0x00000080	/* Has last open failed? */
#define DEV_USED_FOR_LV		0x00000100	/* Is device used for an LV */
#define DEV_ASSUMED_FOR_LV	0x00000200	/* Is device assumed for an LV */
#define DEV_NOT_O_NOATIME	0x00000400	/* Don't use O_NOATIME */

/* ioflags */
#define AIO_SUPPORTED_CODE_PATH	0x00000001	/* Set if the code path supports AIO */

#define aio_supported_code_path(ioflags)       (((ioflags) & AIO_SUPPORTED_CODE_PATH) ? 1 : 0)

/*
 * Standard format for callback functions.
 * When provided, callback functions are called exactly once.
 * If failed is set, data cannot be accessed.
 */
typedef void (*lvm_callback_fn_t)(int failed, unsigned ioflags, void *context, const void *data);

/*
 * Support for external device info.
 * Any new external device info source needs to be
 * registered using EXT_REGISTER macro in dev-ext.c.
 */
typedef enum dev_ext_e {
	DEV_EXT_NONE,
	DEV_EXT_UDEV,
	DEV_EXT_NUM
} dev_ext_t;

struct dev_ext {
	int enabled;
	dev_ext_t src;
	void *handle;
};

/*
 * All I/O is annotated with the reason it is performed.
 */
typedef enum dev_io_reason {
	DEV_IO_SIGNATURES = 0,	/* Scanning device signatures */
	DEV_IO_LABEL,		/* LVM PV disk label */
	DEV_IO_MDA_HEADER,	/* Text format metadata area header */
	DEV_IO_MDA_CONTENT,	/* Text format metadata area content */
	DEV_IO_MDA_EXTRA_HEADER,	/* Header of any extra metadata areas on device */
	DEV_IO_MDA_EXTRA_CONTENT,	/* Content of any extra metadata areas on device */
	DEV_IO_FMT1,		/* Original LVM1 metadata format */
	DEV_IO_POOL,		/* Pool metadata format */
	DEV_IO_LV,		/* Content written to an LV */
	DEV_IO_LOG		/* Logging messages */
} dev_io_reason_t;

/*
 * Is this I/O for a device's extra metadata area?
 */
#define EXTRA_IO(reason) ((reason) == DEV_IO_MDA_EXTRA_HEADER || (reason) == DEV_IO_MDA_EXTRA_CONTENT)
#define DEV_DEVBUF(dev, reason) (EXTRA_IO((reason)) ? &(dev)->last_extra_devbuf : &(dev)->last_devbuf)
#define DEV_DEVBUF_DATA(dev, reason) ((char *) DEV_DEVBUF((dev), (reason))->buf + DEV_DEVBUF((dev), (reason))->data_offset)

struct device_area {
	struct device *dev;
	uint64_t start;		/* Bytes */
	uint64_t size;		/* Bytes */
};

struct device_buffer {
	uint64_t data_offset;	/* Offset to start of requested data within buf */
	void *malloc_address;	/* Start of allocated memory */
	void *buf;		/* Aligned buffer that contains data within it */
	struct device_area where;	/* Location of buf */
	dev_io_reason_t reason;
	unsigned write:1;	/* 1 if write; 0 if read */

	lvm_callback_fn_t dev_read_callback_fn;
	void *dev_read_callback_context;
	struct dm_list aio_queued;	/* Queue of async I/O waiting to be issued */
};

/*
 * All devices in LVM will be represented by one of these.
 * pointer comparisons are valid.
 */
struct device {
	struct dm_list aliases;	/* struct dm_str_list */
	dev_t dev;

	/* private */
	int fd;
	int open_count;
	int error_count;
	int max_error_count;
	int phys_block_size;
	int block_size;
	int read_ahead;
	uint32_t flags;
	unsigned size_seqno;
	uint64_t size;
	uint64_t end;
	struct dm_list open_list;
	struct dev_ext ext;
	struct device_buffer last_devbuf;       /* Last data buffer read from the device */
	struct device_buffer last_extra_devbuf; /* Last data buffer read from the device for extra metadata area */

	const char *vgid; /* if device is an LV */
	const char *lvid; /* if device is an LV */

	char pvid[ID_LEN + 1]; /* if device is a PV */
	char _padding[7];
};

struct device_list {
	struct dm_list list;
	struct device *dev;
};

/*
 * Support for external device info.
 */
const char *dev_ext_name(struct device *dev);
int dev_ext_enable(struct device *dev, dev_ext_t src);
int dev_ext_disable(struct device *dev);
struct dev_ext *dev_ext_get(struct device *dev);
int dev_ext_release(struct device *dev);

/*
 * Increment current dev_size_seqno.
 * This is used to control lifetime
 * of cached device size.
 */
void dev_size_seqno_inc(void);

/*
 * All io should use these routines.
 */
int dev_get_block_size(struct device *dev, unsigned int *phys_block_size, unsigned int *block_size);
int dev_get_size(struct device *dev, uint64_t *size);
int dev_get_read_ahead(struct device *dev, uint32_t *read_ahead);
int dev_discard_blocks(struct device *dev, uint64_t offset_bytes, uint64_t size_bytes);

/* Use quiet version if device number could change e.g. when opening LV */
int dev_open(struct device *dev);
int dev_open_quiet(struct device *dev);
int dev_open_flags(struct device *dev, int flags, int direct, int quiet);
int dev_open_readonly(struct device *dev);
int dev_open_readonly_buffered(struct device *dev);
int dev_open_readonly_quiet(struct device *dev);
int dev_close(struct device *dev);
int dev_close_immediate(struct device *dev);
void dev_close_all(void);
int dev_test_excl(struct device *dev);

int dev_fd(struct device *dev);
const char *dev_name(const struct device *dev);

/* Returns a read-only buffer */
const char *dev_read(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason);
const char *dev_read_circular(struct device *dev, uint64_t offset, size_t len,
			      uint64_t offset2, size_t len2, dev_io_reason_t reason);

/* Passes the data (or error) to dev_read_callback_fn */
void dev_read_callback(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason,
		       unsigned ioflags, lvm_callback_fn_t dev_read_callback_fn, void *callback_context);

/* Read data and copy it into a supplied private buffer. */
/* Only use for tiny reads or on unimportant code paths. */
int dev_read_buf(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason, void *retbuf);

int dev_write(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason, void *buffer);
int dev_append(struct device *dev, size_t len, dev_io_reason_t reason, char *buffer);
int dev_set(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason, int value);
void dev_flush(struct device *dev);

struct device *dev_create_file(const char *filename, struct device *dev,
			       struct dm_str_list *alias, int use_malloc);
void dev_destroy_file(struct device *dev);

void devbufs_release(struct device *dev);

/* Return a valid device name from the alias list; NULL otherwise */
const char *dev_name_confirmed(struct device *dev, int quiet);

struct cmd_context;
int dev_async_getevents(void);
int dev_async_setup(struct cmd_context *cmd);
void dev_async_exit(void);
int dev_async_reset(struct cmd_context *cmd);

#endif