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dissect: use DISKSEQ when waiting for block devices

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DISKSEQ is a reliable way to find out if we missed a uevent or not, as
it's monotonically increasing. If we parse an event with a smaller or
no sequence number, we know we need to wait longer. If we parse an
event with a greater sequence number, we know we missed it and the
device was reused.
This commit is contained in:
Luca Boccassi 2021-07-20 15:26:56 +01:00
parent bcef1743a5
commit a36429971a
10 changed files with 55 additions and 18 deletions
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1
src/core/namespace.c
View File

@ -1905,6 +1905,7 @@ int setup_namespace(
loop_device->fd,
&verity,
root_image_options,
loop_device->diskseq,
loop_device->uevent_seqnum_not_before,
loop_device->timestamp_not_before,
dissect_image_flags,

1
src/dissect/dissect.c
View File

@ -795,6 +795,7 @@ static int run(int argc, char *argv[]) {
arg_image,
&arg_verity_settings,
NULL,
d->diskseq,
d->uevent_seqnum_not_before,
d->timestamp_not_before,
arg_flags,

1
src/gpt-auto-generator/gpt-auto-generator.c
View File

@ -699,6 +699,7 @@ static int enumerate_partitions(dev_t devnum) {
r = dissect_image(
fd,
NULL, NULL,
/* diskseq= */ 0,
UINT64_MAX,
USEC_INFINITY,
DISSECT_IMAGE_GPT_ONLY|

1
src/nspawn/nspawn.c
View File

@ -5700,6 +5700,7 @@ static int run(int argc, char *argv[]) {
arg_image,
&arg_verity_settings,
NULL,
loop->diskseq,
loop->uevent_seqnum_not_before,
loop->timestamp_not_before,
dissect_image_flags,

1
src/portable/portable.c
View File

@ -393,6 +393,7 @@ static int portable_extract_by_path(
r = dissect_image(
d->fd,
NULL, NULL,
d->diskseq,
d->uevent_seqnum_not_before,
d->timestamp_not_before,
DISSECT_IMAGE_READ_ONLY |

1
src/shared/discover-image.c
View File

@ -1203,6 +1203,7 @@ int image_read_metadata(Image *i) {
r = dissect_image(
d->fd,
NULL, NULL,
d->diskseq,
d->uevent_seqnum_not_before,
d->timestamp_not_before,
DISSECT_IMAGE_GENERIC_ROOT |

56
src/shared/dissect-image.c
View File

@ -284,6 +284,7 @@ struct wait_data {
sd_device *parent_device;
blkid_partition blkidp;
sd_device *found;
uint64_t diskseq;
uint64_t uevent_seqnum_not_before;
usec_t timestamp_not_before;
DissectImageFlags flags;
@ -302,7 +303,25 @@ static int device_monitor_handler(sd_device_monitor *monitor, sd_device *device,
if (device_for_action(device, SD_DEVICE_REMOVE))
return 0;
if (w->uevent_seqnum_not_before != UINT64_MAX) {
if (w->diskseq != 0) {
uint64_t diskseq;
/* If w->diskseq is non-zero, then we must have a disk seqnum */
r = sd_device_get_diskseq(device, &diskseq);
if (r < 0) {
log_debug_errno(r, "Dropping event because it has no diskseq, but waiting for %" PRIu64, w->diskseq);
return 0;
}
if (diskseq < w->diskseq) {
log_debug("Dropping event because diskseq too old (%" PRIu64 " < %" PRIu64 ")",
diskseq, w->diskseq);
return 0;
}
if (diskseq > w->diskseq) {
r = -EBUSY;
goto finish; /* Newer than what we were expecting, so we missed it, stop waiting */
}
} else if (w->uevent_seqnum_not_before != UINT64_MAX) {
uint64_t seqnum;
r = sd_device_get_seqnum(device, &seqnum);
@ -378,6 +397,7 @@ static int wait_for_partition_device(
sd_device *parent,
blkid_partition pp,
usec_t deadline,
uint64_t diskseq,
uint64_t uevent_seqnum_not_before,
usec_t timestamp_not_before,
DissectImageFlags flags,
@ -423,6 +443,7 @@ static int wait_for_partition_device(
_cleanup_(wait_data_done) struct wait_data w = {
.parent_device = parent,
.blkidp = pp,
.diskseq = diskseq,
.uevent_seqnum_not_before = uevent_seqnum_not_before,
.timestamp_not_before = timestamp_not_before,
.flags = flags,
@ -450,16 +471,21 @@ static int wait_for_partition_device(
return r;
}
r = sd_event_add_time_relative(
event, &retry_source,
CLOCK_MONOTONIC, 500 * USEC_PER_MSEC, 0,
retry_handler, &w);
if (r < 0)
return r;
/* If we don't have a disk sequence number then we cannot do exact matching,
* and we cannot know if we missed it or if it has not been sent yet, so set
* up additional retries to increase the chances of receiving the event. */
if (diskseq == 0) {
r = sd_event_add_time_relative(
event, &retry_source,
CLOCK_MONOTONIC, 500 * USEC_PER_MSEC, 0,
retry_handler, &w);
if (r < 0)
return r;
r = sd_event_source_set_exit_on_failure(retry_source, true);
if (r < 0)
return r;
r = sd_event_source_set_exit_on_failure(retry_source, true);
if (r < 0)
return r;
}
r = sd_event_loop(event);
if (r < 0)
@ -583,6 +609,7 @@ int dissect_image(
int fd,
const VeritySettings *verity,
const MountOptions *mount_options,
uint64_t diskseq,
uint64_t uevent_seqnum_not_before,
usec_t timestamp_not_before,
DissectImageFlags flags,
@ -838,7 +865,7 @@ int dissect_image(
if (!pp)
return errno_or_else(EIO);
r = wait_for_partition_device(d, pp, deadline, uevent_seqnum_not_before, timestamp_not_before, flags, &q);
r = wait_for_partition_device(d, pp, deadline, diskseq, uevent_seqnum_not_before, timestamp_not_before, flags, &q);
if (r < 0)
return r;
@ -2750,6 +2777,7 @@ int dissect_image_and_warn(
const char *name,
const VeritySettings *verity,
const MountOptions *mount_options,
uint64_t diskseq,
uint64_t uevent_seqnum_not_before,
usec_t timestamp_not_before,
DissectImageFlags flags,
@ -2766,7 +2794,7 @@ int dissect_image_and_warn(
name = buffer;
}
r = dissect_image(fd, verity, mount_options, uevent_seqnum_not_before, timestamp_not_before, flags, ret);
r = dissect_image(fd, verity, mount_options, diskseq, uevent_seqnum_not_before, timestamp_not_before, flags, ret);
switch (r) {
case -EOPNOTSUPP:
@ -2874,7 +2902,7 @@ int mount_image_privately_interactively(
if (r < 0)
return log_error_errno(r, "Failed to set up loopback device for %s: %m", image);
r = dissect_image_and_warn(d->fd, image, &verity, NULL, d->uevent_seqnum_not_before, d->timestamp_not_before, flags, &dissected_image);
r = dissect_image_and_warn(d->fd, image, &verity, NULL, d->diskseq, d->uevent_seqnum_not_before, d->timestamp_not_before, flags, &dissected_image);
if (r < 0)
return r;
@ -2965,6 +2993,7 @@ int verity_dissect_and_mount(
loop_device->fd,
&verity,
options,
loop_device->diskseq,
loop_device->uevent_seqnum_not_before,
loop_device->timestamp_not_before,
dissect_image_flags,
@ -2975,6 +3004,7 @@ int verity_dissect_and_mount(
loop_device->fd,
&verity,
options,
loop_device->diskseq,
loop_device->uevent_seqnum_not_before,
loop_device->timestamp_not_before,
dissect_image_flags | DISSECT_IMAGE_NO_PARTITION_TABLE,

4
src/shared/dissect-image.h
View File

@ -162,8 +162,8 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(MountOptions*, mount_options_free_all);
const char* mount_options_from_designator(const MountOptions *options, PartitionDesignator designator);
int probe_filesystem(const char *node, char **ret_fstype);
int dissect_image(int fd, const VeritySettings *verity, const MountOptions *mount_options, uint64_t uevent_seqnum_not_before, usec_t timestamp_not_before, DissectImageFlags flags, DissectedImage **ret);
int dissect_image_and_warn(int fd, const char *name, const VeritySettings *verity, const MountOptions *mount_options, uint64_t uevent_seqnum_not_before, usec_t timestamp_not_before, DissectImageFlags flags, DissectedImage **ret);
int dissect_image(int fd, const VeritySettings *verity, const MountOptions *mount_options, uint64_t diskseq, uint64_t uevent_seqnum_not_before, usec_t timestamp_not_before, DissectImageFlags flags, DissectedImage **ret);
int dissect_image_and_warn(int fd, const char *name, const VeritySettings *verity, const MountOptions *mount_options, uint64_t diskseq, uint64_t uevent_seqnum_not_before, usec_t timestamp_not_before, DissectImageFlags flags, DissectedImage **ret);
DissectedImage* dissected_image_unref(DissectedImage *m);
DEFINE_TRIVIAL_CLEANUP_FUNC(DissectedImage*, dissected_image_unref);

1
src/sysext/sysext.c
View File

@ -532,6 +532,7 @@ static int merge_subprocess(Hashmap *images, const char *workspace) {
img->path,
&verity_settings,
NULL,
d->diskseq,
d->uevent_seqnum_not_before,
d->timestamp_not_before,
flags,

6
src/test/test-loop-block.c
View File

@ -51,7 +51,7 @@ static void* thread_func(void *ptr) {
log_notice("Acquired loop device %s, will mount on %s", loop->node, mounted);
r = dissect_image(loop->fd, NULL, NULL, loop->uevent_seqnum_not_before, loop->timestamp_not_before, DISSECT_IMAGE_READ_ONLY, &dissected);
r = dissect_image(loop->fd, NULL, NULL, loop->diskseq, loop->uevent_seqnum_not_before, loop->timestamp_not_before, DISSECT_IMAGE_READ_ONLY, &dissected);
if (r < 0)
log_error_errno(r, "Failed dissect loopback device %s: %m", loop->node);
assert_se(r >= 0);
@ -188,7 +188,7 @@ int main(int argc, char *argv[]) {
sfdisk = NULL;
assert_se(loop_device_make(fd, O_RDWR, 0, UINT64_MAX, LO_FLAGS_PARTSCAN, &loop) >= 0);
assert_se(dissect_image(loop->fd, NULL, NULL, loop->uevent_seqnum_not_before, loop->timestamp_not_before, 0, &dissected) >= 0);
assert_se(dissect_image(loop->fd, NULL, NULL, loop->diskseq, loop->uevent_seqnum_not_before, loop->timestamp_not_before, 0, &dissected) >= 0);
assert_se(dissected->partitions[PARTITION_ESP].found);
assert_se(dissected->partitions[PARTITION_ESP].node);
@ -212,7 +212,7 @@ int main(int argc, char *argv[]) {
assert_se(make_filesystem(dissected->partitions[PARTITION_HOME].node, "ext4", "home", id, true) >= 0);
dissected = dissected_image_unref(dissected);
assert_se(dissect_image(loop->fd, NULL, NULL, loop->uevent_seqnum_not_before, loop->timestamp_not_before, 0, &dissected) >= 0);
assert_se(dissect_image(loop->fd, NULL, NULL, loop->diskseq, loop->uevent_seqnum_not_before, loop->timestamp_not_before, 0, &dissected) >= 0);
assert_se(mkdtemp_malloc(NULL, &mounted) >= 0);