On 7 August 2017 at 10:18, Karel Zak <kzak@xxxxxxxxxx> wrote: > On Mon, Aug 07, 2017 at 07:40:17AM +0200, Rafał Miłecki wrote: >> On 3 August 2017 at 14:26, Karel Zak <kzak@xxxxxxxxxx> wrote: >> > On Wed, Aug 02, 2017 at 02:14:18PM +0200, Rafał Miłecki wrote: >> >> From: Rafał Miłecki <rafal@xxxxxxxxxx> >> >> >> >> UBI is a volume management system that can be used on a raw flash >> >> partition for providing multiple logical volumes. Detecting UBI >> >> superblock may be useful for tools wanting to simplify or automate >> >> attaching UBI. >> >> >> >> Please note it's not directly related to the ubifs support which is just >> >> a filesystem working on top of UBI volume. >> >> >> >> In other words: UBI can be used on MTD partition (e.g. /dev/mtdblock0) >> >> while ubifs can be used on UBI volume (e.g. /dev/ubi0_0). >> >> >> >> This patch adds simple code reading UBI version and unique number and >> >> setting it in the blkid_probe. >> >> >> >> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx> >> >> --- >> >> V2: Update commit message (more UBI vs. ubifs details) >> >> Pass &hdr->image_seq to the blkid_probe_sprintf_uuid >> >> Add test >> > >> > Applied, thanks. >> > >> >> +ID_FS_TYPE=ubi >> >> +ID_FS_USAGE=filesystem >> > >> > This is probably not ideal. We use "RAID" flag for logic volume >> > managers. The advantage is that probing is faster as it does not try >> > to check for another signature when "RAID" is detected. >> > >> > The question is how small could be the UBI device? We don't probe for >> > "RAID" on very small devices (<=1MiB). >> >> UBI is responsible for bad blocks handling, so it needs enough erase >> blocks (PEBs) reserved in order to work. If one's MTD partition is as >> small as 1 MiB, it won't have enough of erase blocks (PEBs) [0]. >> >> There is some formula for amount of reserved blocks, like: >> n_reserved = n_max_bad_blocks + n_internal_volumes_blocks + 1 >> but basically 1 MiB is said to be too small. >> >> Does it mean we should & we're save to switch from OTHER to the RAID? > > I have pushed this change to the master branch. Now UBI uses > BLKID_USAGE_RAID flag (and the test image has been enlarged (> 1MiB)). Thank you! I appreciate your help on getting this feature in place :) -- Rafał -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
