Messages in this thread Patch in this message | | | Subject | [PATCH v3 12/15] block: enable dax for raw block devices | From | Dan Williams <> | Date | Sun, 01 Nov 2015 23:30:47 -0500 |
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If an application wants exclusive access to all of the persistent memory provided by an NVDIMM namespace it can use this raw-block-dax facility to forgo establishing a filesystem. This capability is targeted primarily to hypervisors wanting to provision persistent memory for guests. It can be disabled / enabled dynamically via the new BLKDAXSET ioctl.
Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: kbuild test robot <fengguang.wu@intel.com> Reviewed-by: Jan Kara <jack@suse.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- block/ioctl.c | 43 ++++++++++++++++++++++ fs/block_dev.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++- include/linux/fs.h | 3 ++ include/uapi/linux/fs.h | 2 + 4 files changed, 137 insertions(+), 1 deletion(-)
diff --git a/block/ioctl.c b/block/ioctl.c index 8061eba42887..205d57612fbd 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -295,6 +295,35 @@ static inline int is_unrecognized_ioctl(int ret) ret == -ENOIOCTLCMD; } +#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) + return -ENOTTY; + + mutex_lock(&bdev->bd_inode->i_mutex); + if (bdev->bd_map_count == 0) + inode_set_flags(bdev->bd_inode, n, S_DAX); + else + rc = -EBUSY; + mutex_unlock(&bdev->bd_inode->i_mutex); + return rc; +} +#else +static int blkdev_set_dax(struct block_device *bdev, int n) +{ + if (n) + return -ENOTTY; + return 0; +} +#endif + /* * always keep this in sync with compat_blkdev_ioctl() */ @@ -449,6 +478,20 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, case BLKTRACETEARDOWN: ret = blk_trace_ioctl(bdev, cmd, (char __user *) arg); break; + case BLKDAXSET: + if (!capable(CAP_SYS_ADMIN)) + return -EACCES; + + if (get_user(n, (int __user *)(arg))) + return -EFAULT; + n = !!n; + if (n == !!(bdev->bd_inode->i_flags & S_DAX)) + return 0; + + return blkdev_set_dax(bdev, n); + case BLKDAXGET: + return put_int(arg, !!(bdev->bd_inode->i_flags & S_DAX)); + break; default: ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg); } diff --git a/fs/block_dev.c b/fs/block_dev.c index 29cd1eb0765d..13ce6d0ff7f6 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1687,13 +1687,101 @@ static const struct address_space_operations def_blk_aops = { .is_dirty_writeback = buffer_check_dirty_writeback, }; +#ifdef CONFIG_FS_DAX +/* + * In the raw block case we do not need to contend with truncation nor + * unwritten file extents. Without those concerns there is no need for + * additional locking beyond the mmap_sem context that these routines + * are already executing under. + * + * Note, there is no protection if the block device is dynamically + * resized (partition grow/shrink) during a fault. A stable block device + * size is already not enforced in the blkdev_direct_IO path. + * + * For DAX, it is the responsibility of the block device driver to + * ensure the whole-disk device size is stable while requests are in + * flight. + * + * Finally, unlike the filemap_page_mkwrite() case there is no + * filesystem superblock to sync against freezing. We still include a + * pfn_mkwrite callback for dax drivers to receive write fault + * notifications. + */ +static int blkdev_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + return __dax_fault(vma, vmf, blkdev_get_block, NULL); +} + +static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, unsigned int flags) +{ + return __dax_pmd_fault(vma, addr, pmd, flags, blkdev_get_block, NULL); +} + +static void blkdev_vm_open(struct vm_area_struct *vma) +{ + struct inode *bd_inode = bdev_file_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + + mutex_lock(&bd_inode->i_mutex); + bdev->bd_map_count++; + mutex_unlock(&bd_inode->i_mutex); +} + +static void blkdev_vm_close(struct vm_area_struct *vma) +{ + struct inode *bd_inode = bdev_file_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + + mutex_lock(&bd_inode->i_mutex); + bdev->bd_map_count--; + mutex_unlock(&bd_inode->i_mutex); +} + +static const struct vm_operations_struct blkdev_dax_vm_ops = { + .open = blkdev_vm_open, + .close = blkdev_vm_close, + .fault = blkdev_dax_fault, + .pmd_fault = blkdev_dax_pmd_fault, + .pfn_mkwrite = blkdev_dax_fault, +}; + +static const struct vm_operations_struct blkdev_default_vm_ops = { + .open = blkdev_vm_open, + .close = blkdev_vm_close, + .fault = filemap_fault, + .map_pages = filemap_map_pages, +}; + +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; +} +#else +#define blkdev_mmap generic_file_mmap +#endif + const struct file_operations def_blk_fops = { .open = blkdev_open, .release = blkdev_close, .llseek = block_llseek, .read_iter = blkdev_read_iter, .write_iter = blkdev_write_iter, - .mmap = generic_file_mmap, + .mmap = blkdev_mmap, .fsync = blkdev_fsync, .unlocked_ioctl = block_ioctl, #ifdef CONFIG_COMPAT diff --git a/include/linux/fs.h b/include/linux/fs.h index 72d8a844c692..8fb2d4b848bf 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -482,6 +482,9 @@ struct block_device { int bd_fsfreeze_count; /* Mutex for freeze */ struct mutex bd_fsfreeze_mutex; +#ifdef CONFIG_FS_DAX + int bd_map_count; +#endif }; /* diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 9b964a5920af..cc2f0fdae707 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -152,6 +152,8 @@ struct inodes_stat_t { #define BLKSECDISCARD _IO(0x12,125) #define BLKROTATIONAL _IO(0x12,126) #define BLKZEROOUT _IO(0x12,127) +#define BLKDAXSET _IO(0x12,128) +#define BLKDAXGET _IO(0x12,129) #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ #define FIBMAP _IO(0x00,1) /* bmap access */
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