dm table: fall back to getting device using name_to_dev_t()
If a device is used as the root filesystem, it can't be built off of devices which are within the root filesystem (just like command line arguments to root=). For this reason, Linux has a pseudo-filesystem for root= and MD initialization (based on the function name_to_dev_t) which handles different ways of specifying devices including PARTUUID and major:minor. Switch to using name_to_dev_t() in dm_get_device(). Rather than having DM assume that all things which are not major:minor are paths in an already-mounted filesystem, change dm_get_device() to first attempt to look up the device in the filesystem, and if not found it will fall back to using name_to_dev_t(). In terms of backwards compatibility, there are some cases where behavior will be different: - If you have a file in the current working directory named 1:2 and you initialze DM there, then it will try to use that file rather than the disk with that major:minor pair as a backing device. - Similarly for other bdev types which name_to_dev_t() knows how to interpret, the previous behavior was to repeatedly check for the existence of the file (e.g., while waiting for rootfs to come up) but the new behavior is to use the name_to_dev_t() interpretation. For example, if you have a file named /dev/ubiblock0_0 which is a symlink to /dev/sda3, but it is not yet present when DM starts to initialize, then the name_to_dev_t() interpretation will take precedence. These incompatibilities would only show up in really strange setups with bad practices so we shouldn't have to worry about them. Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@ -19,6 +19,7 @@
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#include <linux/delay.h>
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#include <linux/atomic.h>
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#include <linux/blk-mq.h>
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#include <linux/mount.h>
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#define DM_MSG_PREFIX "table"
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@ -373,23 +374,18 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
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int r;
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dev_t uninitialized_var(dev);
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struct dm_dev_internal *dd;
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unsigned int major, minor;
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struct dm_table *t = ti->table;
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char dummy;
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struct block_device *bdev;
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BUG_ON(!t);
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if (sscanf(path, "%u:%u%c", &major, &minor, &dummy) == 2) {
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/* Extract the major/minor numbers */
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dev = MKDEV(major, minor);
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if (MAJOR(dev) != major || MINOR(dev) != minor)
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return -EOVERFLOW;
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/* convert the path to a device */
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bdev = lookup_bdev(path);
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if (IS_ERR(bdev)) {
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dev = name_to_dev_t(path);
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if (!dev)
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return -ENODEV;
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} else {
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/* convert the path to a device */
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struct block_device *bdev = lookup_bdev(path);
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if (IS_ERR(bdev))
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return PTR_ERR(bdev);
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dev = bdev->bd_dev;
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bdput(bdev);
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}
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