On 04/06/2016 06:54 PM, Ivan Shapovalov wrote:
On 2016-02-09 at 18:53 +0100, Edward Shishkin wrote:
Hi all,
There is a pending patch for precise discarsd, which I can not merge
because it is incomplete. Just want to know, is there any progress on
this?
So we found that calculating discard params by mkfs and storing
them in superblock is a dirty option, so I suggest to reserve a
contiguous area (1 MiB?) on disk at "mkfs -d" time (just mark it busy
in the bitmap). And calculate erase unit size and offset at mount
time.
If calculation failed for some reasons, then use non-precise discard.
So, I think, we'll need one d32 field in disk superblock, which
indicates
number of reserved blocks (0 means no reservation) and a pair of
definitions in disk_format40.h:
#define FORMAT40_FIRST_RESERVED_FOR_PROBING \
((REISER4_MASTER_OFFSET / PAGE_CACHE_SIZE) + 6)
#define FORMAT40_MAX_BLOCKS_RESERVED_FOR_PROBING
If any questions, or technical stoppers, then let me know.
Thanks,
Edward.
I guess it would be nicer to allocate the needed space dynamically at
mount time.
And if no enough space, then switch to non-precise discard mode? OK.
Since the probing code is for SSD drives, it shouldn't lead to long mounts
in the case of big terabyte partitions, which are full of data.
However, there is a problem: where to put the probing code
in the fill_super() (I suppose?) sequence?
Put it in try_init_format40(), right after the sa_init_allocator():
seems to be a right place.
Thanks,
Edward.
We want the allocator to be
intact, but nothing should be written to the filesystem so far.
--
Ivan Shapovalov / intelfx /
On 07/05/2015 05:13 PM, Ivan Shapovalov wrote:
On 2015-07-05 at 16:06 +0200, Dušan Čolić wrote:
On 5 Jul 2015 15:12, "Ivan Shapovalov"<intelfx100@xxxxxxxxx> wro
te:
On 2015-07-05 at 02:33 +0800, Edward Shishkin wrote:
On 07/05/2015 01:53 AM, Ivan Shapovalov wrote:
On 2015-07-04 at 15:53 +0800, Edward Shishkin wrote:
[...]
And how to test directly at mount time?
Something along the lines of
- allocate 1 MiB of contiguous space
- fill it with non-zeros
- for N = 1, 2, 4, ...:
- discard N sectors from the contiguous space
- check if anything in the discarded space became zero
-filled
- if it did, infer alignnment from the first zero-
filled
block,
infer granularity from the zero-filled region size.
mkfs seems to be more suitable for this funny business
Yeah, sure. So... new superblock format with two extra fields?
But what happens when someone makes an image of whole partition
and
uses it
on new different ssd?
Maybe we can make a tunefs.reiser4 (just) for that purpose.
--
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