On 1/29/21 9:57 PM, Alasdair G Kergon wrote: > On Fri, Jan 29, 2021 at 06:40:06PM +0800, Coly Li wrote: >> Recently I receive a report that whole system hung and no response after >> a while with I/O load. The special configuration is the dm thin-pool >> volume is used as the swap partition of the system. >> My questions are, >> - Can a thin-pool volume be used as swap device? > > Yes in principle, but it won't get much testing as it's not > necessarily a particularly sensible configuration. > - You'd normally prefer fully-pre-allocated disk space for swap > and turn off the zeroing. > > Is there some use-case where it does make more sense? > What I see is on a system there are dozens of partitions created on top of many thin-pool for each, including the swap partition. People just use thin-pool volumes in this way, and bug triggered. >> - The above description is a bug, or an already know issue which should >> be avoided ? > > Bug. > Thanks for the confirmation. I tried to change all memory allocation into GFP_NOIO or with memalloc_noio_save(), the deadlock still exists. What I suspect yet is might be from the memory allocation from the kworkers, but this is only my guess and no evidence. If there is patch addressed this hung issue (thin-pool volume as swap), I'd like to help testing, because my local environment may 100% reproduce the problem in 5 minutes. Thanks. Coly Li -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
