| /* |
| * fs/dax.c - Direct Access filesystem code |
| * Copyright (c) 2013-2014 Intel Corporation |
| * Author: Matthew Wilcox <matthew.r.wilcox@intel.com> |
| * Author: Ross Zwisler <ross.zwisler@linux.intel.com> |
| * |
| * This program is free software; you can redistribute it and/or modify it |
| * under the terms and conditions of the GNU General Public License, |
| * version 2, as published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| * more details. |
| */ |
| |
| #include <linux/atomic.h> |
| #include <linux/blkdev.h> |
| #include <linux/buffer_head.h> |
| #include <linux/fs.h> |
| #include <linux/genhd.h> |
| #include <linux/highmem.h> |
| #include <linux/memcontrol.h> |
| #include <linux/mm.h> |
| #include <linux/mutex.h> |
| #include <linux/sched.h> |
| #include <linux/uio.h> |
| #include <linux/vmstat.h> |
| |
| 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); |
| |
| might_sleep(); |
| do { |
| void *addr; |
| unsigned long pfn; |
| long count; |
| |
| count = bdev_direct_access(bdev, sector, &addr, &pfn, size); |
| if (count < 0) |
| return count; |
| BUG_ON(size < count); |
| while (count > 0) { |
| unsigned pgsz = PAGE_SIZE - offset_in_page(addr); |
| if (pgsz > count) |
| pgsz = count; |
| if (pgsz < PAGE_SIZE) |
| memset(addr, 0, pgsz); |
| else |
| clear_page(addr); |
| addr += pgsz; |
| size -= pgsz; |
| count -= pgsz; |
| BUG_ON(pgsz & 511); |
| sector += pgsz / 512; |
| cond_resched(); |
| } |
| } while (size); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(dax_clear_blocks); |
| |
| static long dax_get_addr(struct buffer_head *bh, void **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); |
| } |
| |
| static void dax_new_buf(void *addr, unsigned size, unsigned first, loff_t pos, |
| loff_t end) |
| { |
| loff_t final = end - pos + first; /* The final byte of the buffer */ |
| |
| if (first > 0) |
| memset(addr, 0, first); |
| if (final < size) |
| memset(addr + final, 0, size - final); |
| } |
| |
| static bool buffer_written(struct buffer_head *bh) |
| { |
| return buffer_mapped(bh) && !buffer_unwritten(bh); |
| } |
| |
| /* |
| * When ext4 encounters a hole, it returns without modifying the buffer_head |
| * which means that we can't trust b_size. To cope with this, we set b_state |
| * to 0 before calling get_block and, if any bit is set, we know we can trust |
| * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is |
| * and would save us time calling get_block repeatedly. |
| */ |
| static bool buffer_size_valid(struct buffer_head *bh) |
| { |
| return bh->b_state != 0; |
| } |
| |
| 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 *addr; |
| bool hole = false; |
| |
| if (iov_iter_rw(iter) != WRITE) |
| end = min(end, i_size_read(inode)); |
| |
| while (pos < end) { |
| unsigned len; |
| if (pos == max) { |
| unsigned blkbits = inode->i_blkbits; |
| sector_t block = pos >> blkbits; |
| unsigned first = pos - (block << blkbits); |
| long size; |
| |
| 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) |
| break; |
| if (!buffer_size_valid(bh)) |
| bh->b_size = 1 << blkbits; |
| bh_max = pos - first + bh->b_size; |
| } else { |
| unsigned done = bh->b_size - |
| (bh_max - (pos - first)); |
| bh->b_blocknr += done >> blkbits; |
| bh->b_size -= done; |
| } |
| |
| hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh); |
| if (hole) { |
| addr = NULL; |
| size = bh->b_size - first; |
| } else { |
| retval = dax_get_addr(bh, &addr, blkbits); |
| if (retval < 0) |
| break; |
| if (buffer_unwritten(bh) || buffer_new(bh)) |
| dax_new_buf(addr, retval, first, pos, |
| end); |
| addr += first; |
| size = retval - first; |
| } |
| max = min(pos + size, end); |
| } |
| |
| if (iov_iter_rw(iter) == WRITE) |
| len = copy_from_iter(addr, max - pos, iter); |
| else if (!hole) |
| len = copy_to_iter(addr, max - pos, iter); |
| else |
| len = iov_iter_zero(max - pos, iter); |
| |
| if (!len) |
| break; |
| |
| pos += len; |
| addr += len; |
| } |
| |
| return (pos == start) ? retval : 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 |
| * @pos: The file offset where the I/O starts |
| * @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, loff_t pos, get_block_t get_block, |
| dio_iodone_t end_io, int flags) |
| { |
| struct buffer_head bh; |
| ssize_t retval = -EINVAL; |
| loff_t end = pos + iov_iter_count(iter); |
| |
| memset(&bh, 0, sizeof(bh)); |
| |
| if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) { |
| struct address_space *mapping = inode->i_mapping; |
| mutex_lock(&inode->i_mutex); |
| retval = filemap_write_and_wait_range(mapping, pos, end - 1); |
| if (retval) { |
| mutex_unlock(&inode->i_mutex); |
| goto out; |
| } |
| } |
| |
| /* Protects against truncate */ |
| inode_dio_begin(inode); |
| |
| retval = dax_io(inode, iter, pos, end, get_block, &bh); |
| |
| if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) |
| mutex_unlock(&inode->i_mutex); |
| |
| if ((retval > 0) && end_io) |
| end_io(iocb, pos, retval, bh.b_private); |
| |
| inode_dio_end(inode); |
| out: |
| return retval; |
| } |
| EXPORT_SYMBOL_GPL(dax_do_io); |
| |
| /* |
| * The user has performed a load from a hole in the file. Allocating |
| * a new page in the file would cause excessive storage usage for |
| * workloads with sparse files. We allocate a page cache page instead. |
| * We'll kick it out of the page cache if it's ever written to, |
| * otherwise it will simply fall out of the page cache under memory |
| * pressure without ever having been dirtied. |
| */ |
| static int dax_load_hole(struct address_space *mapping, struct page *page, |
| struct vm_fault *vmf) |
| { |
| unsigned long size; |
| struct inode *inode = mapping->host; |
| if (!page) |
| page = find_or_create_page(mapping, vmf->pgoff, |
| GFP_KERNEL | __GFP_ZERO); |
| if (!page) |
| return VM_FAULT_OOM; |
| /* Recheck i_size under page lock to avoid truncate race */ |
| size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| if (vmf->pgoff >= size) { |
| unlock_page(page); |
| page_cache_release(page); |
| return VM_FAULT_SIGBUS; |
| } |
| |
| vmf->page = page; |
| return VM_FAULT_LOCKED; |
| } |
| |
| static int copy_user_bh(struct page *to, struct buffer_head *bh, |
| unsigned blkbits, unsigned long vaddr) |
| { |
| void *vfrom, *vto; |
| if (dax_get_addr(bh, &vfrom, blkbits) < 0) |
| return -EIO; |
| vto = kmap_atomic(to); |
| copy_user_page(vto, vfrom, vaddr, to); |
| kunmap_atomic(vto); |
| 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 *addr; |
| unsigned long pfn; |
| pgoff_t size; |
| int error; |
| |
| i_mmap_lock_read(mapping); |
| |
| /* |
| * Check truncate didn't happen while we were allocating a block. |
| * If it did, this block may or may not be still allocated to the |
| * file. We can't tell the filesystem to free it because we can't |
| * take i_mutex here. In the worst case, the file still has blocks |
| * allocated past the end of the file. |
| */ |
| size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| if (unlikely(vmf->pgoff >= size)) { |
| error = -EIO; |
| 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; |
| goto out; |
| } |
| |
| if (buffer_unwritten(bh) || buffer_new(bh)) |
| clear_page(addr); |
| |
| error = vm_insert_mixed(vma, vaddr, pfn); |
| |
| out: |
| i_mmap_unlock_read(mapping); |
| |
| return error; |
| } |
| |
| static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, |
| get_block_t get_block, dax_iodone_t complete_unwritten) |
| { |
| struct file *file = vma->vm_file; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| struct page *page; |
| 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; |
| |
| 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_size = PAGE_SIZE; |
| |
| repeat: |
| page = find_get_page(mapping, vmf->pgoff); |
| if (page) { |
| if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { |
| page_cache_release(page); |
| return VM_FAULT_RETRY; |
| } |
| if (unlikely(page->mapping != mapping)) { |
| unlock_page(page); |
| page_cache_release(page); |
| goto repeat; |
| } |
| size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| if (unlikely(vmf->pgoff >= size)) { |
| /* |
| * We have a struct page covering a hole in the file |
| * from a read fault and we've raced with a truncate |
| */ |
| error = -EIO; |
| goto unlock_page; |
| } |
| } |
| |
| error = get_block(inode, block, &bh, 0); |
| if (!error && (bh.b_size < PAGE_SIZE)) |
| error = -EIO; /* fs corruption? */ |
| if (error) |
| goto unlock_page; |
| |
| if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) { |
| 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_page; |
| } else { |
| return dax_load_hole(mapping, page, 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); |
| else |
| clear_user_highpage(new_page, vaddr); |
| if (error) |
| goto unlock_page; |
| vmf->page = page; |
| if (!page) { |
| i_mmap_lock_read(mapping); |
| /* Check we didn't race with truncate */ |
| size = (i_size_read(inode) + PAGE_SIZE - 1) >> |
| PAGE_SHIFT; |
| if (vmf->pgoff >= size) { |
| i_mmap_unlock_read(mapping); |
| error = -EIO; |
| goto out; |
| } |
| } |
| return VM_FAULT_LOCKED; |
| } |
| |
| /* Check we didn't race with a read fault installing a new page */ |
| if (!page && major) |
| page = find_lock_page(mapping, vmf->pgoff); |
| |
| if (page) { |
| unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, |
| PAGE_CACHE_SIZE, 0); |
| delete_from_page_cache(page); |
| unlock_page(page); |
| page_cache_release(page); |
| } |
| |
| /* |
| * If we successfully insert the new mapping over an unwritten extent, |
| * we need to ensure we convert the unwritten extent. If there is an |
| * error inserting the mapping, the filesystem needs to leave it as |
| * unwritten to prevent exposure of the stale underlying data to |
| * userspace, but we still need to call the completion function so |
| * the private resources on the mapping buffer can be released. We |
| * indicate what the callback should do via the uptodate variable, same |
| * as for normal BH based IO completions. |
| */ |
| error = dax_insert_mapping(inode, &bh, vma, vmf); |
| if (buffer_unwritten(&bh)) |
| complete_unwritten(&bh, !error); |
| |
| 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; |
| |
| unlock_page: |
| if (page) { |
| unlock_page(page); |
| page_cache_release(page); |
| } |
| goto out; |
| } |
| |
| /** |
| * 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. |
| */ |
| int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, |
| get_block_t get_block, dax_iodone_t complete_unwritten) |
| { |
| int result; |
| struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
| |
| if (vmf->flags & FAULT_FLAG_WRITE) { |
| sb_start_pagefault(sb); |
| file_update_time(vma->vm_file); |
| } |
| result = do_dax_fault(vma, vmf, get_block, complete_unwritten); |
| if (vmf->flags & FAULT_FLAG_WRITE) |
| sb_end_pagefault(sb); |
| |
| return result; |
| } |
| 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 |
| * |
| */ |
| int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) |
| { |
| struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
| |
| sb_start_pagefault(sb); |
| file_update_time(vma->vm_file); |
| sb_end_pagefault(sb); |
| return VM_FAULT_NOPAGE; |
| } |
| EXPORT_SYMBOL_GPL(dax_pfn_mkwrite); |
| |
| /** |
| * 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. |
| * |
| * We work in terms of PAGE_CACHE_SIZE here for commonality with |
| * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem |
| * took care of disposing of the unnecessary blocks. Even if the filesystem |
| * block size is smaller than PAGE_SIZE, we have to zero the rest of the page |
| * since the file might be mmapped. |
| */ |
| 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_CACHE_SHIFT; |
| unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| int err; |
| |
| /* Block boundary? Nothing to do */ |
| if (!length) |
| return 0; |
| BUG_ON((offset + length) > PAGE_CACHE_SIZE); |
| |
| memset(&bh, 0, sizeof(bh)); |
| bh.b_size = PAGE_CACHE_SIZE; |
| err = get_block(inode, index, &bh, 0); |
| if (err < 0) |
| return err; |
| if (buffer_written(&bh)) { |
| void *addr; |
| err = dax_get_addr(&bh, &addr, inode->i_blkbits); |
| if (err < 0) |
| return err; |
| memset(addr + offset, 0, length); |
| } |
| |
| return 0; |
| } |
| 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. |
| * |
| * We work in terms of PAGE_CACHE_SIZE here for commonality with |
| * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem |
| * took care of disposing of the unnecessary blocks. Even if the filesystem |
| * block size is smaller than PAGE_SIZE, we have to zero the rest of the page |
| * since the file might be mmapped. |
| */ |
| int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) |
| { |
| unsigned length = PAGE_CACHE_ALIGN(from) - from; |
| return dax_zero_page_range(inode, from, length, get_block); |
| } |
| EXPORT_SYMBOL_GPL(dax_truncate_page); |