On Mon, Apr 11, 2022 at 10:43:33AM -0400, Mikulas Patocka wrote:
> If you run a program compiled with OpenWatcom for Linux on a filesystem on
> NVMe, all "stat" syscalls fail with -EOVERFLOW. The reason is that the
> NVMe driver allocates a device with the major number 259 and it doesn't
> pass the "old_valid_dev" test.
>
> This patch removes the tests - it's better to wrap around than to return
> an error. (note that cp_old_stat also doesn't report an error and wraps
> the number around)
Is it better? You've done a good job arguing why it is for this particular
situation, but if there's a program which compares files by
st_dev+st_ino, it might think two files are identical when they're
actually different and, eg, skip backing up a file because it thinks
it already did it. That would be a silent failure, which is worse
than this noisy failure.
The real problem is clearly that Linus denied my request for a real
major number for NVMe back in 2012 or whenever it was :-P
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
>
> ---
> fs/stat.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> Index: linux-5.17.2/fs/stat.c
> ===================================================================
> --- linux-5.17.2.orig/fs/stat.c 2022-04-10 21:39:27.000000000 +0200
> +++ linux-5.17.2/fs/stat.c 2022-04-10 21:42:43.000000000 +0200
> @@ -334,7 +334,6 @@ SYSCALL_DEFINE2(fstat, unsigned int, fd,
> # define choose_32_64(a,b) b
> #endif
>
> -#define valid_dev(x) choose_32_64(old_valid_dev(x),true)
> #define encode_dev(x) choose_32_64(old_encode_dev,new_encode_dev)(x)
>
> #ifndef INIT_STRUCT_STAT_PADDING
> @@ -345,8 +344,6 @@ static int cp_new_stat(struct kstat *sta
> {
> struct stat tmp;
>
> - if (!valid_dev(stat->dev) || !valid_dev(stat->rdev))
> - return -EOVERFLOW;
> #if BITS_PER_LONG == 32
> if (stat->size > MAX_NON_LFS)
> return -EOVERFLOW;
> @@ -644,9 +641,6 @@ static int cp_compat_stat(struct kstat *
> {
> struct compat_stat tmp;
>
> - if (!old_valid_dev(stat->dev) || !old_valid_dev(stat->rdev))
> - return -EOVERFLOW;
> -
> memset(&tmp, 0, sizeof(tmp));
> tmp.st_dev = old_encode_dev(stat->dev);
> tmp.st_ino = stat->ino;
>
