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Date: Tue, 3 Nov 2015 11:32:34 +1100 From: Dave Chinner <david@...morbit.com> To: Dan Williams <dan.j.williams@...el.com> Cc: axboe@...com, jack@...e.cz, linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org, ross.zwisler@...ux.intel.com, hch@....de Subject: Re: [PATCH v3 13/15] block, dax: make dax mappings opt-in by default On Sun, Nov 01, 2015 at 11:30:53PM -0500, Dan Williams wrote: > Now that we have the ability to dynamically enable DAX for a raw block > inode, make the behavior opt-in by default. DAX does not have feature > parity with pagecache backed mappings, so applications should knowingly > enable DAX semantics. > > Note, this is only for mappings returned to userspace. For the > synchronous usages of DAX, dax_do_io(), there is no semantic difference > with the bio submission path, so that path remains default enabled. > > Signed-off-by: Dan Williams <dan.j.williams@...el.com> > --- > block/ioctl.c | 3 +-- > fs/block_dev.c | 33 +++++++++++++++++++++++---------- > include/linux/fs.h | 8 ++++++++ > 3 files changed, 32 insertions(+), 12 deletions(-) > > diff --git a/block/ioctl.c b/block/ioctl.c > index 205d57612fbd..c4c3a09d9ca9 100644 > --- a/block/ioctl.c > +++ b/block/ioctl.c > @@ -298,13 +298,12 @@ static inline int is_unrecognized_ioctl(int ret) > #ifdef CONFIG_FS_DAX > static int blkdev_set_dax(struct block_device *bdev, int n) > { > - struct gendisk *disk = bdev->bd_disk; > int rc = 0; > > if (n) > n = S_DAX; > > - if (n && !disk->fops->direct_access) > + if (n && !blkdev_dax_capable(bdev)) > return -ENOTTY; > > mutex_lock(&bdev->bd_inode->i_mutex); > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 13ce6d0ff7f6..ee34a31e6fa4 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -152,16 +152,37 @@ static struct inode *bdev_file_inode(struct file *file) > return file->f_mapping->host; > } > > +#ifdef CONFIG_FS_DAX > +bool blkdev_dax_capable(struct block_device *bdev) > +{ > + struct gendisk *disk = bdev->bd_disk; > + > + if (!disk->fops->direct_access) > + return false; > + > + /* > + * If the partition is not aligned on a page boundary, we can't > + * do dax I/O to it. > + */ > + if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512)) > + || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512))) > + return false; > + > + return true; Where do you check that S_DAX has been enabled on the block device now? Cheers, Dave. -- Dave Chinner david@...morbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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