Messages in this thread | | | Date | Fri, 17 Feb 2006 18:44:35 +0000 | From | Alasdair G Kergon <> | Subject | Re: [PATCH 1/3] sysfs representation of stacked devices (dm/md common) |
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Make sure you test this properly under low memory situations.
On Fri, Feb 17, 2006 at 01:01:48PM -0500, Jun'ichi Nomura wrote: > This patch provides common functions to create symlinks in sysfs > between stacked device and its slaves.
dm_swap_table() mustn't block waiting for memory to become free (except in a controlled way e.g. with a mempool, but it would need more than that here).
Here, dm_swap_table() leads to kmalloc() getting called in sysfs_add_link().
[e.g. Consider the extreme case where the dm device you're changing is your swap device. While dm_swap_table() runs, no I/O will get through to your swap device.]
If you can't avoid the sysfs code allocating memory, then you must find a way of doing it before the dm suspend or after the dm resume. e.g. Do the sysfs memory allocations for the links prior to the dm suspend [which may have happened in a previous system call] and then use a different function to move them into place during dm_swap_table() without performing further memory allocations? [Lazy workaround is to set PF_MEMALLOC again...]
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