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1404e5ee61
lvm opens devices readonly to scan them, but needs to open then readwrite to update the metadata. Previously, the ro fd was closed before the rw fd was opened, leaving a small gap where the dev was not held open, and during which the dev could possibly change which storage it referred to. With the bcache_change_fd() interface, lvm opens a rw fd on a device to be written, tells bcache to change to the new rw fd, and closes the ro fd. . open dev ro . read dev with the ro fd (label_scan) . lock vg (ex for writing) . open dev rw . close ro fd . rescan dev to check if the metadata changed between the scan and the lock . if the metadata did change, reread in full . write the metadata
137 lines
4.1 KiB
C
137 lines
4.1 KiB
C
/*
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* Copyright (C) 2002-2004 Sistina Software, Inc. All rights reserved.
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* Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
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*
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* This file is part of LVM2.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU Lesser General Public License v.2.1.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _LVM_LABEL_H
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#define _LVM_LABEL_H
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#include "lib/uuid/uuid.h"
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#include "lib/device/device.h"
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#include "lib/device/bcache.h"
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#define LABEL_ID "LABELONE"
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#define LABEL_SIZE SECTOR_SIZE /* Think very carefully before changing this */
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#define LABEL_SCAN_SECTORS 4L
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#define LABEL_SCAN_SIZE (LABEL_SCAN_SECTORS << SECTOR_SHIFT)
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struct labeller;
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struct dev_filter;
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struct cmd_context;
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struct logical_volume;
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/* On disk - 32 bytes */
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struct label_header {
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int8_t id[8]; /* LABELONE */
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uint64_t sector_xl; /* Sector number of this label */
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uint32_t crc_xl; /* From next field to end of sector */
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uint32_t offset_xl; /* Offset from start of struct to contents */
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int8_t type[8]; /* LVM2 001 */
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} __attribute__ ((packed));
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/* In core */
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struct label {
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char type[8];
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uint64_t sector;
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struct labeller *labeller;
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struct device *dev;
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void *info;
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};
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struct labeller;
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struct label_ops {
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/*
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* Is the device labelled with this format ?
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*/
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int (*can_handle) (struct labeller * l, void *buf, uint64_t sector);
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/*
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* Write a label to a volume.
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*/
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int (*write) (struct label * label, void *buf);
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/*
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* Read a label from a volume.
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*/
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int (*read) (struct cmd_context *cmd, struct labeller * l, struct device * dev,
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void *label_buf, uint64_t label_sector, int *is_duplicate);
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/*
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* Populate label_type etc.
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*/
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int (*initialise_label) (struct labeller * l, struct label * label);
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/*
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* Destroy a previously read label.
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*/
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void (*destroy_label) (struct labeller * l, struct label * label);
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/*
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* Destructor.
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*/
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void (*destroy) (struct labeller * l);
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};
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struct labeller {
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struct label_ops *ops;
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const struct format_type *fmt;
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};
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int label_init(void);
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void label_exit(void);
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int label_register_handler(struct labeller *handler);
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struct labeller *label_get_handler(const char *name);
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int label_remove(struct device *dev);
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int label_write(struct device *dev, struct label *label);
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struct label *label_create(struct labeller *labeller);
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void label_destroy(struct label *label);
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extern struct bcache *scan_bcache;
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int label_scan(struct cmd_context *cmd);
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int label_scan_devs(struct cmd_context *cmd, struct dev_filter *f, struct dm_list *devs);
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int label_scan_devs_rw(struct cmd_context *cmd, struct dev_filter *f, struct dm_list *devs);
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int label_scan_devs_excl(struct dm_list *devs);
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void label_scan_invalidate(struct device *dev);
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void label_scan_invalidate_lv(struct cmd_context *cmd, struct logical_volume *lv);
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void label_scan_drop(struct cmd_context *cmd);
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void label_scan_destroy(struct cmd_context *cmd);
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int label_read(struct device *dev);
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int label_read_sector(struct device *dev, uint64_t scan_sector);
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void label_scan_confirm(struct device *dev);
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int label_scan_setup_bcache(void);
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int label_scan_open(struct device *dev);
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int label_scan_open_excl(struct device *dev);
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int label_scan_open_rw(struct device *dev);
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int label_scan_reopen_rw(struct device *dev);
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int label_scan_for_pvid(struct cmd_context *cmd, char *pvid, struct device **dev_out);
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/*
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* Wrappers around bcache equivalents.
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* (these make it easier to disable bcache and revert to direct rw if needed)
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*/
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bool dev_read_bytes(struct device *dev, uint64_t start, size_t len, void *data);
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bool dev_write_bytes(struct device *dev, uint64_t start, size_t len, void *data);
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bool dev_write_zeros(struct device *dev, uint64_t start, size_t len);
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bool dev_set_bytes(struct device *dev, uint64_t start, size_t len, uint8_t val);
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bool dev_invalidate_bytes(struct device *dev, uint64_t start, size_t len);
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void dev_set_last_byte(struct device *dev, uint64_t offset);
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void dev_unset_last_byte(struct device *dev);
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#endif
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