>> Chris and I had initially decided to unpack the tails on file open
>> if O_DIRECT is used, but it seems cleaner to add a
>> reiserfs_get_block_direct_io, and have it return -EINVAL if a read
>> went to a tail. writes that happen to a tail will trigger tail
>> conversion.
>
> This is a safe approch (no risk of corruption etc..). However to provide
> the same semantics of the other filesystems it would be even better if
> we could unpack the tail within reiserfs_get_block_direct_io rather than
> returning -EINVAL, but ok, most apps should work fine anyways (and as
> worse people can workaround the magic by remounting reiserfs with notail
> before writing the data that will need to be handled later via
> O_DIRECT).
In the normal case, O_DIRECT can't be done on a file with a tail.
The way I read generic_file_direct_IO, O_DIRECT is only done in
units that start block aligned, and continue for a block aligned
length. So, this can never include a packed file tail.
We should only need to worry if i_size on the file is wrong, and allows a
read/write to a block aligned chunk on a file with a tail, which should
only be legal in the expanding truncate case from older kernels. The
-EINVAL return should only happen in this (very unlikely) case.
-chris
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