Sorry, maybe I did not ask distinctly enough. I mean if I would like to allocate a memory space from ZONE_DMA for atomic context, why can I not use kmalloc(1032, GFP_ATOMIC|GFP_DMA)? In case of lack of GFP_DMA, kmalloc would grab the memory from ZONE_HIGH or ZONE_HIGHMEM, isn't it?(I read it from the textbook of Linux Kernel Development by Robert Love) Or the basic is that you don't think it is necessary to allocate a memory space from DMA area? Please give me some comments. Thank you very much, :-） -----Original Message----- From: Daniel Drake [mailto:dsd@xxxxxxxxxx] Sent: Monday, February 25, 2008 6:15 PM To: nick.cheng@xxxxxxxxxxxx Cc: 'James Bottomley'; linux-scsi@xxxxxxxxxxxxxxx Subject: Re: Patch added to scsi-rc-fixes-2.6: [SCSI] arcmsr: fix message allocation nickcheng wrote: > Hi, > I definitely agree it is in atomic context but why is the memory not for > DMA? > Would you please show me why? It would probably be easier if you could explain where you believe the memory IS used for DMA :) Anyway, looking at ARCMSR_MESSAGE_READ_RQBUFFER current code does this: ver_addr = kmalloc(1032, GFP_ATOMIC); Here are the cases when that buffer is used: checking for successful malloc: not DMA if (!ver_addr) { copying the address: not DMA ptmpQbuffer = ver_addr; memcpying 1 byte into the buffer: not DMA memcpy(ptmpQbuffer, pQbuffer, 1); incrementing address: not DMA ptmpQbuffer++; memcpying from the buffer: not DMA memcpy(pcmdmessagefld->messagedatabuffer, ver_addr, allxfer_len); freeing the buffer: not DMA kfree(ver_addr); Daniel - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
