On 11/05/2014 04:20 PM, Martin K. Petersen wrote: >>>>>> "Boaz" == Boaz Harrosh <boaz@xxxxxxxxxxxxx> writes: > > Hey Boaz, > > Boaz> Note that blk_queue_physical_block_size() also trashes io_min, but > Boaz> we can leave this one to be 512. io_min as opposed to > Boaz> physical_block_size will actually change Kernel behavior > > Care to elaborate? > > Boaz> before this patch running fdisk on a default size brd of 4M > Boaz> the first sector offered is 34 (BAD), but after this patch it > Boaz> will be 40, ie 8 sectors aligned. Also when entering some random > Boaz> partition sizes the next partition-start sector is offered 8 sectors > Boaz> aligned after this patch. (Please note that with fdisk the user > Boaz> can still enter bad values, only the offered default values will > Boaz> be correct) I did elaborate, Please try with these numbers above and see for yourself. (Summery brd-size=4M before this patch will offer 34 as first-sector, after 40) > Also, fdisk and parted should be aligning on 1MB by default regardless > of block size. So I'm also not sure why you need to trick fdisk to align > by setting the pbs. > fdisk will not align partition-start on 1M, only the very first-sector, libgparted and cfdisk are as you say, but with fdisk if you put any odd numbered partition-size, the next start-sector will just be the sum, but with this patch it will offer a small hole and will align the partition-start on 4K. (And even with this patch user can enter bad values) Please believe me that I did not try to invent work for myself. I wanted to fix the partition bugs, with the use of direct_access and to my dismay I found that it is very easy to have broken partition alignments. With this patch it is still possible but mach harder to do so. Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
