btrfs: use named constant for reserved device space

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There's a reserved space on each device of size 1MiB that can be used by
bootloaders or to avoid accidental overwrite. Use a symbolic constant
with the explaining comment instead of hard coding the value and
multiple comments.

Note: since btrfs-progs v4.1, mkfs.btrfs will reserve the first 1MiB for
the primary super block (at offset 64KiB), until then the range could
have been used by mistake. Kernel has been always respecting the 1MiB
range for writes.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

...

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Qu Wenruo 2022-06-13 15:06:34 +08:00 • committed by David Sterba

parent bfceac7fd3

commit 37f85ec320

4 changed files with 15 additions and 17 deletions

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7

fs/btrfs/ctree.h

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6

fs/btrfs/extent-tree.c

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12

fs/btrfs/super.c

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7

fs/btrfs/volumes.c

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