mirror of
https://github.com/clearlinux/kvmtool.git
synced 2026-06-16 02:15:47 +00:00
Asias He
5236b50516
With Direct I/O, file reads and writes go directly from the applications to the storage device, bypassing the operating system read and write caches. This is useful for applications that manage their own caches. Open a disk image with O_DIRECT: $ lkvm run -d ~/img/test.img,direct The original readonly flag is still supported. Open a disk image with O_DIRECT and readonly: $ lkvm run -d ~/img/test.img,direct,ro Signed-off-by: Asias He <asias.hejun@gmail.com> Acked-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Pekka Enberg <penberg@kernel.org>
77 lines
1.6 KiB
C
77 lines
1.6 KiB
C
#include "kvm/disk-image.h"
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#include <linux/err.h>
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#include <mntent.h>
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/*
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* raw image and blk dev are similar, so reuse raw image ops.
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*/
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static struct disk_image_operations blk_dev_ops = {
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.read = raw_image__read,
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.write = raw_image__write,
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};
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static bool is_mounted(struct stat *st)
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{
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struct stat st_buf;
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struct mntent *mnt;
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FILE *f;
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f = setmntent("/proc/mounts", "r");
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if (!f)
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return false;
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while ((mnt = getmntent(f)) != NULL) {
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if (stat(mnt->mnt_fsname, &st_buf) == 0 &&
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S_ISBLK(st_buf.st_mode) && st->st_rdev == st_buf.st_rdev) {
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fclose(f);
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return true;
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}
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}
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fclose(f);
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return false;
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}
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struct disk_image *blkdev__probe(const char *filename, int flags, struct stat *st)
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{
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struct disk_image *disk;
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int fd, r;
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u64 size;
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if (!S_ISBLK(st->st_mode))
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return ERR_PTR(-EINVAL);
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if (is_mounted(st)) {
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pr_err("Block device %s is already mounted! Unmount before use.",
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filename);
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return ERR_PTR(-EINVAL);
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}
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/*
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* Be careful! We are opening host block device!
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* Open it readonly since we do not want to break user's data on disk.
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*/
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fd = open(filename, flags);
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if (fd < 0)
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return ERR_PTR(fd);
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if (ioctl(fd, BLKGETSIZE64, &size) < 0) {
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r = -errno;
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close(fd);
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return ERR_PTR(r);
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}
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/*
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* FIXME: This will not work on 32-bit host because we can not
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* mmap large disk. There is not enough virtual address space
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* in 32-bit host. However, this works on 64-bit host.
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*/
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disk = disk_image__new(fd, size, &blk_dev_ops, DISK_IMAGE_REGULAR);
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#ifdef CONFIG_HAS_AIO
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if (!IS_ERR_OR_NULL(disk))
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disk->async = 1;
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#endif
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return disk;
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}
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