Messages in this thread | | | Date | Tue, 31 Mar 2015 23:22:48 +0100 | From | Al Viro <> | Subject | Re: [PATCH 0/3] block: loop: switch to VFS ITER_BVEC |
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On Wed, Mar 25, 2015 at 04:27:48PM +0100, Christoph Hellwig wrote: > On Wed, Mar 25, 2015 at 03:23:48PM +0800, Ming Lei wrote: > > > - mm_segment_t old_fs = get_fs(); > > > + > > > + iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len); > > > > > > file_start_write(file); > > > - set_fs(get_ds()); > > > - bw = file->f_op->write(file, buf, len, &pos); > > > - set_fs(old_fs); > > > + bw = vfs_iter_write(file, &i, ppos); > > > > This patch moves to support ->read_iter/->write_iter only, which > > might cause regression for backing file without defining read/write > > iter callback. > > ->read_iter/->write_iter is the main fs I/O path - by the time this is > ready ->aio_read/->aio_write should be gone.
Umm... FWIW, it's not about ->aio_write - that conversion is practically complete; nothing with ->aio_write != NULL is plausible for backing store of /dev/loop anyway. Regression in question is about the files that have ->write(), but no ->write_iter(). Most of that won't be usable as backing store, but there are some exceptions: * ncpfs regular files. Ought to be switched to {read,write}_iter - it's a pretty mechanical work, I'll do that. Only marginally useful, but what the hell - why not do it right? * coda. Ought to switch to ->..._iter() and demand _its_ backing store to have those. Trivial, will do. * 9p. Cthulhu-awful mess. The trouble is, we'd need to support ITER_BVEC ones down in p9_client_write(). I'm actually trying to do that right now; if it works, this regression will become a non-issue.
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