Re: [PATCH] Use of getblk differs between locations

From: Mikulas Patocka
Date: Mon Oct 10 2005 - 18:34:41 EST

What should a filesystem driver do if it can't suddenly read or write any
blocks on media?

Maybe stopping gracefully, warn about what happened, and let the system
keep going. You may be right about your main filesystem, but in the case
I'm running, for example, my system in an ext3 filesystem, and have a
vfat from a usb key. Should my system really hang because I'm not able
to read/write to the device?

getblk won't fail because of I/O error --- it can fail only because of
memory management bugs. I think it's right to stop the system in that case
--- it's better than silently corrupting data on any device.


In the code, we see:

if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
(size < 512 || size > PAGE_SIZE))) {

This is where __getblk_slow, and thus, __getblk fails, and it does not
seem to be due to any memory management bug.

This is a filesystem bug --- filesystem should set it's blocksize with sb_set_blocksize (and refuse to mount if the device doesn't support it) before using it in requests.

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