From b2e0d1625e193b40cbbd45b799f82d54d34e015c Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 15 Jan 2016 16:55:59 -0800 Subject: [PATCH] dax: fix lifetime of in-kernel dax mappings with dax_map_atomic() The DAX implementation needs to protect new calls to ->direct_access() and usage of its return value against the driver for the underlying block device being disabled. Use blk_queue_enter()/blk_queue_exit() to hold off blk_cleanup_queue() from proceeding, or otherwise fail new mapping requests if the request_queue is being torn down. This also introduces blk_dax_ctl to simplify the interface from fs/dax.c through dax_map_atomic() to bdev_direct_access(). [willy@linux.intel.com: fix read() of a hole] Signed-off-by: Dan Williams Reviewed-by: Jeff Moyer Cc: Jan Kara Cc: Jens Axboe Cc: Dave Chinner Cc: Ross Zwisler Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/block_dev.c | 13 ++-- fs/dax.c | 208 ++++++++++++++++++++++++++++++------------------- include/linux/blkdev.h | 17 +++- 3 files changed, 150 insertions(+), 88 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index ddc6cdd..530145b 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -455,10 +455,7 @@ EXPORT_SYMBOL_GPL(bdev_write_page); /** * bdev_direct_access() - Get the address for directly-accessibly memory * @bdev: The device containing the memory - * @sector: The offset within the device - * @addr: Where to put the address of the memory - * @pfn: The Page Frame Number for the memory - * @size: The number of bytes requested + * @dax: control and output parameters for ->direct_access * * If a block device is made up of directly addressable memory, this function * will tell the caller the PFN and the address of the memory. The address @@ -469,10 +466,10 @@ EXPORT_SYMBOL_GPL(bdev_write_page); * Return: negative errno if an error occurs, otherwise the number of bytes * accessible at this address. */ -long bdev_direct_access(struct block_device *bdev, sector_t sector, - void __pmem **addr, unsigned long *pfn, long size) +long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax) { - long avail; + sector_t sector = dax->sector; + long avail, size = dax->size; const struct block_device_operations *ops = bdev->bd_disk->fops; /* @@ -491,7 +488,7 @@ long bdev_direct_access(struct block_device *bdev, sector_t sector, sector += get_start_sect(bdev); if (sector % (PAGE_SIZE / 512)) return -EINVAL; - avail = ops->direct_access(bdev, sector, addr, pfn); + avail = ops->direct_access(bdev, sector, &dax->addr, &dax->pfn); if (!avail) return -ERANGE; if (avail > 0 && avail & ~PAGE_MASK) diff --git a/fs/dax.c b/fs/dax.c index 1080fb5..5c548d8 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -30,45 +30,65 @@ #include #include +static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax) +{ + struct request_queue *q = bdev->bd_queue; + long rc = -EIO; + + dax->addr = (void __pmem *) ERR_PTR(-EIO); + if (blk_queue_enter(q, true) != 0) + return rc; + + rc = bdev_direct_access(bdev, dax); + if (rc < 0) { + dax->addr = (void __pmem *) ERR_PTR(rc); + blk_queue_exit(q); + return rc; + } + return rc; +} + +static void dax_unmap_atomic(struct block_device *bdev, + const struct blk_dax_ctl *dax) +{ + if (IS_ERR(dax->addr)) + return; + blk_queue_exit(bdev->bd_queue); +} + /* * dax_clear_blocks() is called from within transaction context from XFS, * and hence this means the stack from this point must follow GFP_NOFS * semantics for all operations. */ -int dax_clear_blocks(struct inode *inode, sector_t block, long size) +int dax_clear_blocks(struct inode *inode, sector_t block, long _size) { struct block_device *bdev = inode->i_sb->s_bdev; - sector_t sector = block << (inode->i_blkbits - 9); + struct blk_dax_ctl dax = { + .sector = block << (inode->i_blkbits - 9), + .size = _size, + }; might_sleep(); do { - void __pmem *addr; - unsigned long pfn; long count, sz; - count = bdev_direct_access(bdev, sector, &addr, &pfn, size); + count = dax_map_atomic(bdev, &dax); if (count < 0) return count; sz = min_t(long, count, SZ_128K); - clear_pmem(addr, sz); - size -= sz; - sector += sz / 512; + clear_pmem(dax.addr, sz); + dax.size -= sz; + dax.sector += sz / 512; + dax_unmap_atomic(bdev, &dax); cond_resched(); - } while (size); + } while (dax.size); wmb_pmem(); return 0; } EXPORT_SYMBOL_GPL(dax_clear_blocks); -static long dax_get_addr(struct buffer_head *bh, void __pmem **addr, - unsigned blkbits) -{ - unsigned long pfn; - sector_t sector = bh->b_blocknr << (blkbits - 9); - return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size); -} - /* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */ static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first, loff_t pos, loff_t end) @@ -98,19 +118,29 @@ static bool buffer_size_valid(struct buffer_head *bh) return bh->b_state != 0; } + +static sector_t to_sector(const struct buffer_head *bh, + const struct inode *inode) +{ + sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); + + return sector; +} + static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, loff_t start, loff_t end, get_block_t get_block, struct buffer_head *bh) { - ssize_t retval = 0; - loff_t pos = start; - loff_t max = start; - loff_t bh_max = start; - void __pmem *addr; - bool hole = false; - bool need_wmb = false; - - if (iov_iter_rw(iter) != WRITE) + loff_t pos = start, max = start, bh_max = start; + bool hole = false, need_wmb = false; + struct block_device *bdev = NULL; + int rw = iov_iter_rw(iter), rc; + long map_len = 0; + struct blk_dax_ctl dax = { + .addr = (void __pmem *) ERR_PTR(-EIO), + }; + + if (rw == READ) end = min(end, i_size_read(inode)); while (pos < end) { @@ -125,13 +155,13 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, if (pos == bh_max) { bh->b_size = PAGE_ALIGN(end - pos); bh->b_state = 0; - retval = get_block(inode, block, bh, - iov_iter_rw(iter) == WRITE); - if (retval) + rc = get_block(inode, block, bh, rw == WRITE); + if (rc) break; if (!buffer_size_valid(bh)) bh->b_size = 1 << blkbits; bh_max = pos - first + bh->b_size; + bdev = bh->b_bdev; } else { unsigned done = bh->b_size - (bh_max - (pos - first)); @@ -139,47 +169,53 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, bh->b_size -= done; } - hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh); + hole = rw == READ && !buffer_written(bh); if (hole) { - addr = NULL; size = bh->b_size - first; } else { - retval = dax_get_addr(bh, &addr, blkbits); - if (retval < 0) + dax_unmap_atomic(bdev, &dax); + dax.sector = to_sector(bh, inode); + dax.size = bh->b_size; + map_len = dax_map_atomic(bdev, &dax); + if (map_len < 0) { + rc = map_len; break; + } if (buffer_unwritten(bh) || buffer_new(bh)) { - dax_new_buf(addr, retval, first, pos, - end); + dax_new_buf(dax.addr, map_len, first, + pos, end); need_wmb = true; } - addr += first; - size = retval - first; + dax.addr += first; + size = map_len - first; } max = min(pos + size, end); } if (iov_iter_rw(iter) == WRITE) { - len = copy_from_iter_pmem(addr, max - pos, iter); + len = copy_from_iter_pmem(dax.addr, max - pos, iter); need_wmb = true; } else if (!hole) - len = copy_to_iter((void __force *)addr, max - pos, + len = copy_to_iter((void __force *) dax.addr, max - pos, iter); else len = iov_iter_zero(max - pos, iter); if (!len) { - retval = -EFAULT; + rc = -EFAULT; break; } pos += len; - addr += len; + if (!IS_ERR(dax.addr)) + dax.addr += len; } if (need_wmb) wmb_pmem(); + dax_unmap_atomic(bdev, &dax); - return (pos == start) ? retval : pos - start; + return (pos == start) ? rc : pos - start; } /** @@ -268,28 +304,35 @@ static int dax_load_hole(struct address_space *mapping, struct page *page, return VM_FAULT_LOCKED; } -static int copy_user_bh(struct page *to, struct buffer_head *bh, - unsigned blkbits, unsigned long vaddr) +static int copy_user_bh(struct page *to, struct inode *inode, + struct buffer_head *bh, unsigned long vaddr) { - void __pmem *vfrom; + struct blk_dax_ctl dax = { + .sector = to_sector(bh, inode), + .size = bh->b_size, + }; + struct block_device *bdev = bh->b_bdev; void *vto; - if (dax_get_addr(bh, &vfrom, blkbits) < 0) - return -EIO; + if (dax_map_atomic(bdev, &dax) < 0) + return PTR_ERR(dax.addr); vto = kmap_atomic(to); - copy_user_page(vto, (void __force *)vfrom, vaddr, to); + copy_user_page(vto, (void __force *)dax.addr, vaddr, to); kunmap_atomic(vto); + dax_unmap_atomic(bdev, &dax); return 0; } static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, struct vm_area_struct *vma, struct vm_fault *vmf) { - struct address_space *mapping = inode->i_mapping; - sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); unsigned long vaddr = (unsigned long)vmf->virtual_address; - void __pmem *addr; - unsigned long pfn; + struct address_space *mapping = inode->i_mapping; + struct block_device *bdev = bh->b_bdev; + struct blk_dax_ctl dax = { + .sector = to_sector(bh, inode), + .size = bh->b_size, + }; pgoff_t size; int error; @@ -308,20 +351,18 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, goto out; } - error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size); - if (error < 0) - goto out; - if (error < PAGE_SIZE) { - error = -EIO; + if (dax_map_atomic(bdev, &dax) < 0) { + error = PTR_ERR(dax.addr); goto out; } if (buffer_unwritten(bh) || buffer_new(bh)) { - clear_pmem(addr, PAGE_SIZE); + clear_pmem(dax.addr, PAGE_SIZE); wmb_pmem(); } + dax_unmap_atomic(bdev, &dax); - error = vm_insert_mixed(vma, vaddr, pfn); + error = vm_insert_mixed(vma, vaddr, dax.pfn); out: i_mmap_unlock_read(mapping); @@ -415,7 +456,7 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, if (vmf->cow_page) { struct page *new_page = vmf->cow_page; if (buffer_written(&bh)) - error = copy_user_bh(new_page, &bh, blkbits, vaddr); + error = copy_user_bh(new_page, inode, &bh, vaddr); else clear_user_highpage(new_page, vaddr); if (error) @@ -527,11 +568,9 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, unsigned blkbits = inode->i_blkbits; unsigned long pmd_addr = address & PMD_MASK; bool write = flags & FAULT_FLAG_WRITE; - long length; - void __pmem *kaddr; + struct block_device *bdev; pgoff_t size, pgoff; - sector_t block, sector; - unsigned long pfn; + sector_t block; int result = 0; /* dax pmd mappings are broken wrt gup and fork */ @@ -559,9 +598,9 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); bh.b_size = PMD_SIZE; - length = get_block(inode, block, &bh, write); - if (length) + if (get_block(inode, block, &bh, write) != 0) return VM_FAULT_SIGBUS; + bdev = bh.b_bdev; i_mmap_lock_read(mapping); /* @@ -616,32 +655,40 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, result = VM_FAULT_NOPAGE; spin_unlock(ptl); } else { - sector = bh.b_blocknr << (blkbits - 9); - length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, - bh.b_size); + struct blk_dax_ctl dax = { + .sector = to_sector(&bh, inode), + .size = PMD_SIZE, + }; + long length = dax_map_atomic(bdev, &dax); + if (length < 0) { result = VM_FAULT_SIGBUS; goto out; } - if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) + if ((length < PMD_SIZE) || (dax.pfn & PG_PMD_COLOUR)) { + dax_unmap_atomic(bdev, &dax); goto fallback; + } /* * TODO: teach vmf_insert_pfn_pmd() to support * 'pte_special' for pmds */ - if (pfn_valid(pfn)) + if (pfn_valid(dax.pfn)) { + dax_unmap_atomic(bdev, &dax); goto fallback; + } if (buffer_unwritten(&bh) || buffer_new(&bh)) { - clear_pmem(kaddr, PMD_SIZE); + clear_pmem(dax.addr, PMD_SIZE); wmb_pmem(); count_vm_event(PGMAJFAULT); mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); result |= VM_FAULT_MAJOR; } + dax_unmap_atomic(bdev, &dax); - result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write); + result |= vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write); } out: @@ -743,12 +790,17 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, if (err < 0) return err; if (buffer_written(&bh)) { - void __pmem *addr; - err = dax_get_addr(&bh, &addr, inode->i_blkbits); - if (err < 0) - return err; - clear_pmem(addr + offset, length); + struct block_device *bdev = bh.b_bdev; + struct blk_dax_ctl dax = { + .sector = to_sector(&bh, inode), + .size = PAGE_CACHE_SIZE, + }; + + if (dax_map_atomic(bdev, &dax) < 0) + return PTR_ERR(dax.addr); + clear_pmem(dax.addr + offset, length); wmb_pmem(); + dax_unmap_atomic(bdev, &dax); } return 0; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index c70e358..88821fa 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1617,6 +1617,20 @@ static inline bool integrity_req_gap_front_merge(struct request *req, #endif /* CONFIG_BLK_DEV_INTEGRITY */ +/** + * struct blk_dax_ctl - control and output parameters for ->direct_access + * @sector: (input) offset relative to a block_device + * @addr: (output) kernel virtual address for @sector populated by driver + * @pfn: (output) page frame number for @addr populated by driver + * @size: (input) number of bytes requested + */ +struct blk_dax_ctl { + sector_t sector; + void __pmem *addr; + long size; + unsigned long pfn; +}; + struct block_device_operations { int (*open) (struct block_device *, fmode_t); void (*release) (struct gendisk *, fmode_t); @@ -1643,8 +1657,7 @@ extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int, extern int bdev_read_page(struct block_device *, sector_t, struct page *); extern int bdev_write_page(struct block_device *, sector_t, struct page *, struct writeback_control *); -extern long bdev_direct_access(struct block_device *, sector_t, - void __pmem **addr, unsigned long *pfn, long size); +extern long bdev_direct_access(struct block_device *, struct blk_dax_ctl *); #else /* CONFIG_BLOCK */ struct block_device; -- 2.7.4