Messages in this thread | | | Date | Mon, 2 Nov 2015 23:35:04 -0800 | Subject | Re: [PATCH v3 13/15] block, dax: make dax mappings opt-in by default | From | Dan Williams <> |
| |
On Mon, Nov 2, 2015 at 4:32 PM, Dave Chinner <david@fromorbit.com> wrote: > 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@intel.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? >
Only in the mmap path:
static int blkdev_mmap(struct file *file, struct vm_area_struct *vma) { struct inode *bd_inode = bdev_file_inode(file); struct block_device *bdev = I_BDEV(bd_inode);
file_accessed(file); mutex_lock(&bd_inode->i_mutex); bdev->bd_map_count++; if (IS_DAX(bd_inode)) { vma->vm_ops = &blkdev_dax_vm_ops; vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; } else { vma->vm_ops = &blkdev_default_vm_ops; } mutex_unlock(&bd_inode->i_mutex);
return 0; }
| |