From: Vladislav B. <vs...@vl...> - 2007-02-22 17:10:07
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Ross S. W. Walker wrote: >>-----Original Message----- >>From: Vu Pham [mailto:hu...@ya...] >>Sent: Thursday, February 22, 2007 11:19 AM >>To: Vladislav Bolkhovitin >>Cc: scs...@li...; Johan Kragsterman; Ross >>S. W. Walker >>Subject: Re: [Scst-devel] Block-io Module >> >>Vladislav Bolkhovitin wrote: >> >>>Vu, BTW, why do you use generic_make_request() instead of >> >>submit_bio() >> >>>as it was in the original code? >>> >> >>Because I want to control the bio->bi_rw flag with >>BIO_RW_SYNC and don't want to change the state of page >>members pgpgout/pgpgin (since these pages does not belong to >>buffer cache, dynamicly allocated/de-allocated). >> >>I guess I can still change bio->bi_rw with BIO_RW_SYNC flag >>and use submit_bio() as well >> > > > You can also pass that flag in with submit_bio(rw|BIO_RW_SYNC, bio), > bio->bi_rw just gets replaced with whatever you pass with submit_bio. > > I have also seen bad things happen with BIO_RW_SYNC, there is a known > bug in some kernels with MD raid1 and the fact it doesn't pass down this > flag on cloned bios. Hm, looking at BIO_RW_SYNC usage in the kernel, it looks like in our case it's only good to always submit bio's with this flag set (our bio's are always synchronous). Eg, IO schedulers actively use this flag to reorder requests. What kind of bad things have you seen with this flag? On which kernel versions (if you remember)? > That's why I went with the call to bdev_q->unplug_fn() to make sure it > gets processed. > > > -Ross > > > ______________________________________________________________________ > This e-mail, and any attachments thereto, is intended only for use by > the addressee(s) named herein and may contain legally privileged > and/or confidential information. If you are not the intended recipient > of this e-mail, you are hereby notified that any dissemination, > distribution or copying of this e-mail, and any attachments thereto, > is strictly prohibited. If you have received this e-mail in error, > please immediately notify the sender and permanently delete the > original and any copy or printout thereof. > > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys-and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Scst-devel mailing list > Scs...@li... > https://lists.sourceforge.net/lists/listinfo/scst-devel > |