On 2022/9/27 22:38, Jeff Moyer wrote:
"Yang, Xiao/杨 晓" <yangx.jy@xxxxxxxxxxx> writes:
Hi Jeff,
Thanks a lot for your reply.
On 2022/9/27 3:52, Jeff Moyer wrote:
"Yang, Xiao/杨 晓" <yangx.jy@xxxxxxxxxxx> writes:
Hi Ross, Toshi, Jeff and others
After reading the kernel patches[1][2][3] about dm, I think only three
types(linear, stripe and log-writes) of dm can support DAX now, right?
Right.
I wonder why only three types of dm need to support DAX? Is there any
reason/history and use case?
It was easy to add DAX support to those targets. Note that if a target
needs to intercept I/O, then it is fundamentally incompatible with DAX.
How can I know which target needs to intercept I/O?
There's no better way than reading and understanding what each target
does.
Hi Jeff,
After reading the code about thin provisioning target, thin provisioning
target depends on DM_BUFIO kconfig which is designed to cache I/O. Is it
what you said about "intercept I/O"? Perhaps, we have to drop DM_BUFIO
for thin provisioning target if we want to make it support DAX.
Best Regards,
Xiao Yang
Could you tell me why it is fundamentally incompatible with DAX?
DAX stands for direct access, and it is a mechanism by which a
user-space process can perform I/O without going through the kernel.
-Jeff
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