virtio-block filesystem corruption

[midnightveil]

On a guest VM with virtio-block, creating 100 folders with:

cd /mnt/testing && rm -rf * && sync && for i in $(seq 1 100); do mkdir "$i"; done && sync && ls

yields the expected result:

1    15   21   28   34   40   47   53   6    66   72   79   85   91   98
10   16   22   29   35   41   48   54   60   67   73   8    86   92   99
100  17   23   3    36   42   49   55   61   68   74   80   87   93
11   18   24   30   37   43   5    56   62   69   75   81   88   94
12   19   25   31   38   44   50   57   63   7    76   82   89   95
13   2    26   32   39   45   51   58   64   70   77   83   9    96
14   20   27   33   4    46   52   59   65   71   78   84   90   97

But powering the guest off cleanly with poweroff, power-cycling the board then ls /mnt/testing does not display the full set of folders as before (or dropping the Linux caches)

1   11  13  2   4   6   79  80  82  84  86  88  9   91  93
10  12  14  3   5   7   8   81  83  85  87  89  90  92  94

The same bug occurs in QEMU, so it's unlikely to be a bug in the imx sdhc driver. (and it doesn't occur in the native LionsOS fileio python repl).

We should try using Eric's fixes to the virtio-blk driver: https://github.com/au-ts/libvmm/pull/128, as it's possible that changes to Linux have broken the driver.

Originally posted by @dreamliner787-9 in https://github.com/au-ts/sddf/pull/368#issuecomment-2709435879