Re: [PATCH 0/3] Fix a deadlock related to modifying queue attributes

[Bart Van Assche <bvanassche@acm.org>]

On 7/10/25 1:03 AM, Christoph Hellwig wrote:
> On Tue, Jul 08, 2025 at 09:11:41AM -0700, Bart Van Assche wrote:
>> * Slower booting of Linux devices that modify sysfs attributes
>>    synchronously during boot.
> 
> So which attributes are regularly modified?  Note that for read-ahead
> it should be safe to drop the freeze as unlike the others it is not
> used for splitting I/O to the limits accepted by the hardware.  So
> we could probably drop the freeze IFF the patch documents that it is
> safe.  But it still won't fix the root cause.

I can't answer the above question for all Linux distros. But I can
answer this question for Android. Here is what I found in the AOSP
platform code, which includes startup (.rc) scripts for all Android
vendors:

$ repo-grep -nHE 'write (/sys/block|/sys/class/block)' '**rc' | \
     sed 's,.*/,,;s/ .*//' | sort | uniq -c | sort -rn | head -n5
      46 read_ahead_kb      # Implemented in block/blk-sysfs.c
      27 scheduler          # Implemented in block/blk-sysfs.c
      20 slice_idle         # BFQ I/O scheduler
      17 comp_algorithm     # zram kernel driver
       4 discard_max_bytes  # Implemented in block/blk-sysfs.c

Thanks,

Bart.