On Wed 19-01-11 11:42:50, Lukas Czerner wrote: > On Wed, 19 Jan 2011, Tao Ma wrote: > > > From: Tao Ma <boyu.mt@xxxxxxxxxx> > > > > We adjust 'len' with s_first_data_block - start in case of start is less > > than s_first_data_block, but it could underflow in case blocksize=1K, while > > fstrim_range.len=512 and fstrim_range.start = 0. In this case len happens > > to be underflow and in the end, although we are safe that last_group check > > will limit the trim to the whole volume, I am afraid that isn't what the user > > really want. > > > > So this patch fix it. It also adds a new variable s_first_data_block so that > > the 4 le32_to_cpu can be replaced with 1. > > Well, I just realized that what are we doing is not exactly what will > user expect. User does not really care where the first data block is. > What the user will expect is, to trim let's say first one gigabyte > of his filesystem, not gigabyte - first data block. > > So what I suggest is to always add first_data_block to > fstrim_range.start and do all the necessary checks for overflow. If no > one has any objections I'll put it to the patch. Well, since we speak about at most 1KB (s_first_data_block is non-zero only when blocksize == 1024 and in that case it is 1), I don't think it really matters and I don't mind whatever solution. What user expects is a bit hard to guess (whether he views 'start' as a start of the filesystem or a start of the device). Maybe the former makes a tad bit more sense but as I said I don't really care so since you're the author of the code I leave it up to you. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
