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On my machine stat returns size 22, but only 20 bytes are read:
openat(AT_FDCWD, "/sys/firmware/efi/efivars/LoaderTimeInitUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f", O_RDONLY|O_NOCTTY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=22, ...}) = 0
read(3, "\6\0\0\0", 4) = 4
read(3, "7\0001\0001\0003\0005\0002\0007\0\0\0", 18) = 16
Failed to read LoaderTimeInitUSec: Input/output error
Let's just accept that the kernel is returning inconsistent results.
It seems to happen two only two variables on my machine:
/sys/firmware/efi/efivars/LoaderTimeInitUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f
/sys/firmware/efi/efivars/LoaderTimeMenuUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f
so it might be related to the way we write them.
If we call LOOP_CLR_FD and LOOP_CTL_REMOVE too rapidly, the kernel cannot deal
with that (5.3.13-300.fc31.x86_64 running on dual core
Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz).
$ sudo strace -eioctl build/test-dissect-image /tmp/foobar3.img
ioctl(3, TCGETS, 0x7ffcee47de20) = -1 ENOTTY (Inappropriate ioctl for device)
ioctl(4, LOOP_CTL_GET_FREE) = 9
ioctl(5, LOOP_SET_FD, 3) = 0
ioctl(5, LOOP_SET_STATUS64, {lo_offset=0, lo_number=0, lo_flags=LO_FLAGS_READ_ONLY|LO_FLAGS_AUTOCLEAR|LO_FLAGS_PARTSCAN, lo_file_name="", ...}) = 0
ioctl(5, BLKGETSIZE64, [299999744]) = 0
ioctl(5, CDROM_GET_CAPABILITY, 0) = -1 EINVAL (Invalid argument)
ioctl(5, BLKSSZGET, [512]) = 0
Waiting for device (parent + 0 partitions) to appear...
Found root partition, writable of type btrfs at #-1 (/dev/block/7:9)
ioctl(5, LOOP_CLR_FD) = 0
ioctl(3, LOOP_CTL_REMOVE, 9) = -1 EBUSY (Device or resource busy)
Failed to remove loop device: Device or resource busy
This seems to be clear race condition, and attaching strace is generally enough
to "win" the race. But even with strace attached, we will fail occasionally.
Let's wait a bit and retry. With the wait, on my machine, the second attempt
always succeeds:
...
Found root partition, writable of type btrfs at #-1 (/dev/block/7:9)
ioctl(5, LOOP_CLR_FD) = 0
ioctl(3, LOOP_CTL_REMOVE, 9) = -1 EBUSY (Device or resource busy)
ioctl(3, LOOP_CTL_REMOVE, 9) = 9
+++ exited with 0 +++
Without the wait, all 64 attempts will occasionally fail.
The function no longer returns the fd. This complicated semantics, because it
wasn't clear what holds the ownership: the return value or the output
parameter. There were no users of the fd in the return value, so let's
simplify things conceptually and only return the fd once.
Reduce the scope of variables.
LOOP_CLR_FD was called on the wrong fd. Let's use a cleanup function to make
this automatic and reduce chances of a mixup in the future.
CID 1408498.
This makes --overlay=+/foobar::/foobar work again, i.e. where the middle
parameter is left out. According to the documentation this is supposed
to generate a temporary writable work place in the midle. But it
apparently never did. Weird.
@bertob wants us to be strict here, and only have one "#" header per
markdown file, and use "##" (or "###", …) for all others. Interestingly,
we mostly got this right already, but this fixes a few cases where this
wasn't correct.
These tests two have shown to be flaky in Ubuntu test infrastructure,
but got more reliable with increased timeouts of 300 seconds each.
Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
