Re: [PATCH] Fix queueing work if !bdi_cap_writeback_dirty()

[OGAWA Hirofumi]

Fengguang Wu <fengguang.wu@xxxxxxxxx> writes:

>> > And BDI_CAP_NO_WRITEBACK is expected to be a static/constant flag that
>> > always evaluate to true/false for a given bdi.  There will be
>> > correctness problems if you change the BDI_CAP_NO_WRITEBACK flag
>> > dynamically.
>> 
>> I'm going to use it as static or per-sb by initialized in
>> fill_super(). And it uses always BDI_CAP_NO_WRITEBACK if sb is
>> available. Because own FS task flush instead.
>
> Ah OK, sorry I didn't quite catch your use case.
>
> But then if you set BDI_CAP_NO_WRITEBACK in the beginning, how come
> __bdi_start_writeback() will be called at all?

If we call mark_inode_dirty(inode), inode goes into bdi->wb.b_dirty.
And sync(2) calls __bdi_start_writeback() for all of bdi if bdi->wb.b_*
is not empty.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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