c83f6bf98d
Add a new operation code (BLKPG_RESIZE_PARTITION) to the BLKPG ioctl that allows altering the size of an existing partition, even if it is currently in use. This patch converts hd_struct->nr_sects into sequence counter because One might extend a partition while IO is happening to it and update of nr_sects can be non-atomic on 32bit machines with 64bit sector_t. This can lead to issues like reading inconsistent size of a partition. Sequence counter have been used so that readers don't have to take bdev mutex lock as we call sector_in_part() very frequently. Now all the access to hd_struct->nr_sects should happen using sequence counter read/update helper functions part_nr_sects_read/part_nr_sects_write. There is one exception though, set_capacity()/get_capacity(). I think theoritically race should exist there too but this patch does not modify set_capacity()/get_capacity() due to sheer number of call sites and I am afraid that change might break something. I have left that as a TODO item. We can handle it later if need be. This patch does not introduce any new races as such w.r.t set_capacity()/get_capacity(). v2: Add CONFIG_LBDAF test to UP preempt case as suggested by Phillip. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Phillip Susi <psusi@ubuntu.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
#ifndef _LINUX_BLKPG_H
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#define _LINUX_BLKPG_H
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/*
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* Partition table and disk geometry handling
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*
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* A single ioctl with lots of subfunctions:
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*
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* Device number stuff:
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* get_whole_disk() (given the device number of a partition,
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* find the device number of the encompassing disk)
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* get_all_partitions() (given the device number of a disk, return the
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* device numbers of all its known partitions)
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*
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* Partition stuff:
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* add_partition()
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* delete_partition()
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* test_partition_in_use() (also for test_disk_in_use)
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*
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* Geometry stuff:
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* get_geometry()
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* set_geometry()
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* get_bios_drivedata()
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*
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* For today, only the partition stuff - aeb, 990515
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*/
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#include <linux/compiler.h>
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#include <linux/ioctl.h>
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#define BLKPG _IO(0x12,105)
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/* The argument structure */
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struct blkpg_ioctl_arg {
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int op;
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int flags;
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int datalen;
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void __user *data;
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};
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/* The subfunctions (for the op field) */
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#define BLKPG_ADD_PARTITION 1
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#define BLKPG_DEL_PARTITION 2
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#define BLKPG_RESIZE_PARTITION 3
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/* Sizes of name fields. Unused at present. */
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#define BLKPG_DEVNAMELTH 64
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#define BLKPG_VOLNAMELTH 64
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/* The data structure for ADD_PARTITION and DEL_PARTITION */
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struct blkpg_partition {
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long long start; /* starting offset in bytes */
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long long length; /* length in bytes */
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int pno; /* partition number */
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char devname[BLKPG_DEVNAMELTH]; /* partition name, like sda5 or c0d1p2,
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to be used in kernel messages */
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char volname[BLKPG_VOLNAMELTH]; /* volume label */
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};
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#endif /* _LINUX_BLKPG_H */
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