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repart: Discard from/to first/last usable lba

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Repart considers the start and end of the usable space to the first multiple
of grainsz (at least 4096 bytes). However the first usable LBA of a GPT
partition is at sector 34 (512 bytes sectors) which is not a multiple of 4096.
The backup GPT label at the end also takes up 33 sectors, meaning the last
usable LBA is at 34 sectors from the end, unlikely to be a 4096 multiple as
well.

This meant that the very first and last sectors were never discarded. However
more problematically if an existing partition started before the first
usable grainsz multiple its start didn't get taken into account as a valid
starting point and got its data discarded.

Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>
This commit is contained in:
Sjoerd Simons 2023-02-23 10:00:16 +01:00 committed by Lennart Poettering
parent 39857544ee
commit 771805eb44
1 changed files with 6 additions and 2 deletions
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8
src/partition/repart.c
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@ -3036,7 +3036,11 @@ static int context_discard_gap_after(Context *context, Partition *p) {
if (p)
gap = p->offset + p->new_size;
else
gap = context->start;
/* The context start gets rounded up to grain_size, however
* existing partitions may be before that so ensure the gap
* starts at the first actually usable lba
*/
gap = fdisk_get_first_lba(context->fdisk_context) * context->sector_size;
LIST_FOREACH(partitions, q, context->partitions) {
if (q->dropped)
@ -3053,7 +3057,7 @@ static int context_discard_gap_after(Context *context, Partition *p) {
}
if (next == UINT64_MAX) {
next = context->end;
next = (fdisk_get_last_lba(context->fdisk_context) + 1) * context->sector_size;
if (gap > next)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Partition end beyond disk end.");
}