Messages in this thread | | | From | Dan Williams <> | Date | Wed, 9 Aug 2017 20:06:24 -0700 | Subject | Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has BDI_CAP_SYNC capability |
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On Wed, Aug 9, 2017 at 8:04 PM, Matthew Wilcox <willy@infradead.org> wrote: > On Wed, Aug 09, 2017 at 11:41:50AM +0900, Minchan Kim wrote: >> On Tue, Aug 08, 2017 at 07:31:22PM -0700, Matthew Wilcox wrote: >> > On Wed, Aug 09, 2017 at 10:51:13AM +0900, Minchan Kim wrote: >> > > On Tue, Aug 08, 2017 at 06:29:04AM -0700, Matthew Wilcox wrote: >> > > > On Tue, Aug 08, 2017 at 05:49:59AM -0700, Matthew Wilcox wrote: >> > > > > + struct bio sbio; >> > > > > + struct bio_vec sbvec; >> > > > >> > > > ... this needs to be sbvec[nr_pages], of course. >> > > > >> > > > > - bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), >> > > > > + if (bdi_cap_synchronous_io(inode_to_bdi(inode))) { >> > > > > + bio = &sbio; >> > > > > + bio_init(bio, &sbvec, nr_pages); >> > > > >> > > > ... and this needs to be 'sbvec', not '&sbvec'. >> > > >> > > I don't get it why we need sbvec[nr_pages]. >> > > On-stack-bio works with per-page. >> > > May I miss something? >> > >> > The way I redid it, it will work with an arbitrary number of pages. >> >> IIUC, it would be good things with dynamic bio alloction with passing >> allocated bio back and forth but on-stack bio cannot work like that. >> It should be done in per-page so it is worth? > > I'm not passing the bio back and forth between do_mpage_readpage() and > its callers. The version I sent allows for multiple pages in a single > on-stack bio (when called from mpage_readpages()).
I like it, but do you think we should switch to sbvec[<constant>] to preclude pathological cases where nr_pages is large?
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