dilim/systemd
1
0
Fork 0
mirror of https://github.com/systemd/systemd.git synced 2026-08-10 17:14:31 +00:00
Code Issues Packages Projects Releases Wiki Activity

repart: Don't get old grain size from fdisk for --copy-from=

Browse Source 
This is a little bit confusing, but grain size is not actually stored in the gpt
metadata. Rather, fdisk's `get_grain_size()` returns an autodiscovered "optimal io
size" value as grain size. This might not actually be the grain size that the
disk we're copying is using.

Since we're setting the padding of the copied partitions using that value from
fdisk, we're rounding the new paddings by fdisk's optimal grain size, which is
usually 1MiB (a lot more then the default 4KiB that we're using otherwise).

Set the grain size here to 1 byte instead, ensuring that the min/max padding set
is exactly the padding that was present before.

Also add a test to confirm the behavior is fixed: The test calls --copy-from= on
an existing disk with 4MiB grain size, and because we pass --grain-size=512, now
no rounding should happen and the paddings should be transferred to exactly the
same size.
This commit is contained in:
Jonas Dreßler
2026-07-07 14:41:16 +02:00
parent 9a09141cae
commit 2b1be5d909
2 changed files with 46 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
src/repart/repart.c
View File

@@ -3355,7 +3355,7 @@ static int context_copy_from_one(Context *context, const char *src) {
_cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
_cleanup_(fdisk_unref_tablep) struct fdisk_table *t = NULL;
Partition *last = NULL;
unsigned long secsz, grainsz;
unsigned long secsz;
size_t n_partitions;
int r;
@@ -3374,7 +3374,6 @@ static int context_copy_from_one(Context *context, const char *src) {
return log_error_errno(r, "Failed to create fdisk context: %m");
secsz = sym_fdisk_get_sector_size(c);
grainsz = sym_fdisk_get_grain_size(c);
/* Insist on a power of two, and that it's a multiple of 512, i.e. the traditional sector size. */
if (secsz < 512 || !ISPOWEROF2(secsz))
@@ -3455,7 +3454,9 @@ static int context_copy_from_one(Context *context, const char *src) {
if (!np->split_name_format)
return log_oom();
r = determine_current_padding(c, t, p, secsz, grainsz, &padding);
/* Pass grain size of 1 to disable rounding by grain as we don't know the grain size
* of the old image. We'll round paddings to the grain size of the new image later. */
r = determine_current_padding(c, t, p, secsz, /* grainsz= */ 1, &padding);
if (r < 0)
return r;

42
test/units/TEST-58-REPART.sh
View File

@@ -451,6 +451,48 @@ $imgs/zzz8 : start= 6422488, size= 131072, type=4D21B016-B534-45C2-A9FB
losetup -d "$loop"
}
testcase_copy_from_grain_padding() {
local defs imgs output
defs="$(mktemp --directory "/tmp/test-repart.defs.XXXXXXXXXX")"
imgs="$(mktemp --directory "/var/tmp/test-repart.imgs.XXXXXXXXXX")"
# shellcheck disable=SC2064
trap "rm -rf '$defs' '$imgs'" RETURN
chmod 0755 "$defs"
truncate -s 80MiB "$imgs/copy_from"
sfdisk "$imgs/copy_from" <<EOF
label: gpt
grain: 4194304
size=40961, type=${root_guid}, uuid=837c3d67-21b3-478e-be82-7e7f83bf96d3
size=10240, type=${xbootldr_guid}, uuid=4985c03e-eecb-4fe0-9f65-3f6345782214
EOF
output=$(sfdisk --dump "$imgs/copy_from")
# Padding between partition 1 and 2 is 8191 sectors
assert_in "$imgs/copy_from1 : start= 8192, size= 40961, type=${root_guid}," "$output"
assert_in "$imgs/copy_from2 : start= 57344, size= 10240, type=${xbootldr_guid}," "$output"
truncate -s 100MiB "$imgs/copy_to"
output=$(systemd-repart --offline="$OFFLINE" \
--empty=allow \
--definitions="$defs" \
--seed="$seed" \
--dry-run=no \
--json=pretty \
--copy-from="$imgs/copy_from" \
--grain-size=512 \
"$imgs/copy_to")
output=$(sfdisk --dump "$imgs/copy_to")
assert_in "$imgs/copy_to1 : start= 2048, size= 40961, type=${root_guid}," "$output"
# We set new grain-size to 1 sector, so padding now should be 8191 sectors again
assert_in "$imgs/copy_to2 : start= 51200, size= 10240, type=${xbootldr_guid}," "$output"
}
testcase_dropin() {
local defs imgs output