diff options
| -rw-r--r-- | Documentation/filesystems/dax.txt | 22 | ||||
| -rw-r--r-- | fs/dax.c | 315 | ||||
| -rw-r--r-- | include/linux/dax.h | 12 |
3 files changed, 11 insertions, 338 deletions
diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt index 23d18b8a49d5..a7e6e14aeb08 100644 --- a/Documentation/filesystems/dax.txt +++ b/Documentation/filesystems/dax.txt @@ -58,22 +58,22 @@ Implementation Tips for Filesystem Writers Filesystem support consists of - adding support to mark inodes as being DAX by setting the S_DAX flag in i_flags -- implementing the direct_IO address space operation, and calling - dax_do_io() instead of blockdev_direct_IO() if S_DAX is set +- implementing ->read_iter and ->write_iter operations which use dax_iomap_rw() + when inode has S_DAX flag set - implementing an mmap file operation for DAX files which sets the VM_MIXEDMAP and VM_HUGEPAGE flags on the VMA, and setting the vm_ops to - include handlers for fault, pmd_fault and page_mkwrite (which should - probably call dax_fault(), dax_pmd_fault() and dax_mkwrite(), passing the - appropriate get_block() callback) -- calling dax_truncate_page() instead of block_truncate_page() for DAX files -- calling dax_zero_page_range() instead of zero_user() for DAX files + include handlers for fault, pmd_fault, page_mkwrite, pfn_mkwrite. These + handlers should probably call dax_iomap_fault() (for fault and page_mkwrite + handlers), dax_iomap_pmd_fault(), dax_pfn_mkwrite() passing the appropriate + iomap operations. +- calling iomap_zero_range() passing appropriate iomap operations instead of + block_truncate_page() for DAX files - ensuring that there is sufficient locking between reads, writes, truncates and page faults -The get_block() callback passed to the DAX functions may return -uninitialised extents. If it does, it must ensure that simultaneous -calls to get_block() (for example by a page-fault racing with a read() -or a write()) work correctly. +The iomap handlers for allocating blocks must make sure that allocated blocks +are zeroed out and converted to written extents before being returned to avoid +exposure of uninitialized data through mmap. These filesystems may be used for inspiration: - ext2: see Documentation/filesystems/ext2.txt @@ -116,168 +116,6 @@ struct page *read_dax_sector(struct block_device *bdev, sector_t n) return page; } -static bool buffer_written(struct buffer_head *bh) -{ - return buffer_mapped(bh) && !buffer_unwritten(bh); -} - -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) -{ - loff_t pos = start, max = start, bh_max = start; - bool hole = false; - struct block_device *bdev = NULL; - int rw = iov_iter_rw(iter), rc; - long map_len = 0; - struct blk_dax_ctl dax = { - .addr = ERR_PTR(-EIO), - }; - unsigned blkbits = inode->i_blkbits; - sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1) - >> blkbits; - - if (rw == READ) - end = min(end, i_size_read(inode)); - - while (pos < end) { - size_t len; - if (pos == max) { - long page = pos >> PAGE_SHIFT; - sector_t block = page << (PAGE_SHIFT - blkbits); - unsigned first = pos - (block << blkbits); - long size; - - if (pos == bh_max) { - bh->b_size = PAGE_ALIGN(end - pos); - bh->b_state = 0; - rc = get_block(inode, block, bh, rw == WRITE); - if (rc) - break; - bh_max = pos - first + bh->b_size; - bdev = bh->b_bdev; - /* - * We allow uninitialized buffers for writes - * beyond EOF as those cannot race with faults - */ - WARN_ON_ONCE( - (buffer_new(bh) && block < file_blks) || - (rw == WRITE && buffer_unwritten(bh))); - } else { - unsigned done = bh->b_size - - (bh_max - (pos - first)); - bh->b_blocknr += done >> blkbits; - bh->b_size -= done; - } - - hole = rw == READ && !buffer_written(bh); - if (hole) { - size = bh->b_size - first; - } else { - 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; - } - dax.addr += first; - size = map_len - first; - } - /* - * pos + size is one past the last offset for IO, - * so pos + size can overflow loff_t at extreme offsets. - * Cast to u64 to catch this and get the true minimum. - */ - max = min_t(u64, pos + size, end); - } - - if (iov_iter_rw(iter) == WRITE) { - len = copy_from_iter_pmem(dax.addr, max - pos, iter); - } else if (!hole) - len = copy_to_iter((void __force *) dax.addr, max - pos, - iter); - else - len = iov_iter_zero(max - pos, iter); - - if (!len) { - rc = -EFAULT; - break; - } - - pos += len; - if (!IS_ERR(dax.addr)) - dax.addr += len; - } - - dax_unmap_atomic(bdev, &dax); - - return (pos == start) ? rc : pos - start; -} - -/** - * dax_do_io - Perform I/O to a DAX file - * @iocb: The control block for this I/O - * @inode: The file which the I/O is directed at - * @iter: The addresses to do I/O from or to - * @get_block: The filesystem method used to translate file offsets to blocks - * @end_io: A filesystem callback for I/O completion - * @flags: See below - * - * This function uses the same locking scheme as do_blockdev_direct_IO: - * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the - * caller for writes. For reads, we take and release the i_mutex ourselves. - * If DIO_LOCKING is not set, the filesystem takes care of its own locking. - * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O - * is in progress. - */ -ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, - struct iov_iter *iter, get_block_t get_block, - dio_iodone_t end_io, int flags) -{ - struct buffer_head bh; - ssize_t retval = -EINVAL; - loff_t pos = iocb->ki_pos; - loff_t end = pos + iov_iter_count(iter); - - memset(&bh, 0, sizeof(bh)); - bh.b_bdev = inode->i_sb->s_bdev; - - if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) - inode_lock(inode); - - /* Protects against truncate */ - if (!(flags & DIO_SKIP_DIO_COUNT)) - inode_dio_begin(inode); - - retval = dax_io(inode, iter, pos, end, get_block, &bh); - - if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) - inode_unlock(inode); - - if (end_io) { - int err; - - err = end_io(iocb, pos, retval, bh.b_private); - if (err) - retval = err; - } - - if (!(flags & DIO_SKIP_DIO_COUNT)) - inode_dio_end(inode); - return retval; -} -EXPORT_SYMBOL_GPL(dax_do_io); - /* * DAX radix tree locking */ @@ -920,105 +758,6 @@ static int dax_insert_mapping(struct address_space *mapping, } /** - * dax_fault - handle a page fault on a DAX file - * @vma: The virtual memory area where the fault occurred - * @vmf: The description of the fault - * @get_block: The filesystem method used to translate file offsets to blocks - * - * When a page fault occurs, filesystems may call this helper in their - * fault handler for DAX files. dax_fault() assumes the caller has done all - * the necessary locking for the page fault to proceed successfully. - */ -int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, - get_block_t get_block) -{ - struct file *file = vma->vm_file; - struct address_space *mapping = file->f_mapping; - struct inode *inode = mapping->host; - void *entry; - struct buffer_head bh; - unsigned long vaddr = (unsigned long)vmf->virtual_address; - unsigned blkbits = inode->i_blkbits; - sector_t block; - pgoff_t size; - int error; - int major = 0; - - /* - * Check whether offset isn't beyond end of file now. Caller is supposed - * to hold locks serializing us with truncate / punch hole so this is - * a reliable test. - */ - size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; - if (vmf->pgoff >= size) - return VM_FAULT_SIGBUS; - - memset(&bh, 0, sizeof(bh)); - block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits); - bh.b_bdev = inode->i_sb->s_bdev; - bh.b_size = PAGE_SIZE; - - entry = grab_mapping_entry(mapping, vmf->pgoff, 0); - if (IS_ERR(entry)) { - error = PTR_ERR(entry); - goto out; - } - - error = get_block(inode, block, &bh, 0); - if (!error && (bh.b_size < PAGE_SIZE)) - error = -EIO; /* fs corruption? */ - if (error) - goto unlock_entry; - - if (vmf->cow_page) { - struct page *new_page = vmf->cow_page; - if (buffer_written(&bh)) - error = copy_user_dax(bh.b_bdev, to_sector(&bh, inode), - bh.b_size, new_page, vaddr); - else - clear_user_highpage(new_page, vaddr); - if (error) - goto unlock_entry; - if (!radix_tree_exceptional_entry(entry)) { - vmf->page = entry; - return VM_FAULT_LOCKED; - } - vmf->entry = entry; - return VM_FAULT_DAX_LOCKED; - } - - if (!buffer_mapped(&bh)) { - if (vmf->flags & FAULT_FLAG_WRITE) { - error = get_block(inode, block, &bh, 1); - count_vm_event(PGMAJFAULT); - mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); - major = VM_FAULT_MAJOR; - if (!error && (bh.b_size < PAGE_SIZE)) - error = -EIO; - if (error) - goto unlock_entry; - } else { - return dax_load_hole(mapping, entry, vmf); - } - } - - /* Filesystem should not return unwritten buffers to us! */ - WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh)); - error = dax_insert_mapping(mapping, bh.b_bdev, to_sector(&bh, inode), - bh.b_size, &entry, vma, vmf); - unlock_entry: - put_locked_mapping_entry(mapping, vmf->pgoff, entry); - out: - if (error == -ENOMEM) - return VM_FAULT_OOM | major; - /* -EBUSY is fine, somebody else faulted on the same PTE */ - if ((error < 0) && (error != -EBUSY)) - return VM_FAULT_SIGBUS | major; - return VM_FAULT_NOPAGE | major; -} -EXPORT_SYMBOL_GPL(dax_fault); - -/** * dax_pfn_mkwrite - handle first write to DAX page * @vma: The virtual memory area where the fault occurred * @vmf: The description of the fault @@ -1078,60 +817,6 @@ int __dax_zero_page_range(struct block_device *bdev, sector_t sector, } EXPORT_SYMBOL_GPL(__dax_zero_page_range); -/** - * dax_zero_page_range - zero a range within a page of a DAX file - * @inode: The file being truncated - * @from: The file offset that is being truncated to - * @length: The number of bytes to zero - * @get_block: The filesystem method used to translate file offsets to blocks - * - * This function can be called by a filesystem when it is zeroing part of a - * page in a DAX file. This is intended for hole-punch operations. If - * you are truncating a file, the helper function dax_truncate_page() may be - * more convenient. - */ -int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, - get_block_t get_block) -{ - struct buffer_head bh; - pgoff_t index = from >> PAGE_SHIFT; - unsigned offset = from & (PAGE_SIZE-1); - int err; - - /* Block boundary? Nothing to do */ - if (!length) - return 0; - if (WARN_ON_ONCE((offset + length) > PAGE_SIZE)) - return -EINVAL; - - memset(&bh, 0, sizeof(bh)); - bh.b_bdev = inode->i_sb->s_bdev; - bh.b_size = PAGE_SIZE; - err = get_block(inode, index, &bh, 0); - if (err < 0 || !buffer_written(&bh)) - return err; - - return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode), - offset, length); -} -EXPORT_SYMBOL_GPL(dax_zero_page_range); - -/** - * dax_truncate_page - handle a partial page being truncated in a DAX file - * @inode: The file being truncated - * @from: The file offset that is being truncated to - * @get_block: The filesystem method used to translate file offsets to blocks - * - * Similar to block_truncate_page(), this function can be called by a - * filesystem when it is truncating a DAX file to handle the partial page. - */ -int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) -{ - unsigned length = PAGE_ALIGN(from) - from; - return dax_zero_page_range(inode, from, length, get_block); -} -EXPORT_SYMBOL_GPL(dax_truncate_page); - #ifdef CONFIG_FS_IOMAP static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos) { diff --git a/include/linux/dax.h b/include/linux/dax.h index 8d1a5c47945f..0afade8bd3d7 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -38,13 +38,8 @@ static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags) ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, struct iomap_ops *ops); -ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *, - get_block_t, dio_iodone_t, int flags); -int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t); -int dax_truncate_page(struct inode *, loff_t from, get_block_t); int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, struct iomap_ops *ops); -int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t); int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index); void dax_wake_mapping_entry_waiter(struct address_space *mapping, pgoff_t index, void *entry, bool wake_all); @@ -73,12 +68,6 @@ static inline int __dax_zero_page_range(struct block_device *bdev, } #endif -static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, - pmd_t *pmd, unsigned int flags, get_block_t gb) -{ - return VM_FAULT_FALLBACK; -} - #ifdef CONFIG_FS_DAX_PMD static inline unsigned int dax_radix_order(void *entry) { @@ -101,7 +90,6 @@ static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma, } #endif int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *); -#define dax_mkwrite(vma, vmf, gb) dax_fault(vma, vmf, gb) static inline bool vma_is_dax(struct vm_area_struct *vma) { |