efi: Distinguish between "remaining space" and actually used space
EFI implementations distinguish between space that is actively used by a variable and space that merely hasn't been garbage collected yet. Space that hasn't yet been garbage collected isn't available for use and so isn't counted in the remaining_space field returned by QueryVariableInfo(). Combined with commit 68d92986 this can cause problems. Some implementations don't garbage collect until the remaining space is smaller than the maximum variable size, and as a result check_var_size() will always fail once more than 50% of the variable store has been used even if most of that space is marked as available for garbage collection. The user is unable to create new variables, and deleting variables doesn't increase the remaining space. The problem that 68d92986 was attempting to avoid was one where certain platforms fail if the actively used space is greater than 50% of the available storage space. We should be able to calculate that by simply summing the size of each available variable and subtracting that from the total storage space. With luck this will fix the problem described in https://bugzilla.kernel.org/show_bug.cgi?id=55471 without permitting damage to occur to the machines 68d92986 was attempting to fix. Signed-off-by:Matthew Garrett <matthew.garrett@nebula.com> Signed-off-by:
Matt Fleming <matt.fleming@intel.com>
parent
cc5a080c
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