/* * 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(int rw, 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 (rw != 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, rw == 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 = (rw != 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 (rw == 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 * @rw: READ to read or WRITE to write * @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(int rw, 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) && (rw == 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 */ atomic_inc(&inode->i_dio_count); retval = dax_io(rw, inode, iter, pos, end, get_block, &bh); if ((flags & DIO_LOCKING) && (rw == READ)) mutex_unlock(&inode->i_mutex); if ((retval > 0) && end_io) end_io(iocb, pos, retval, bh.b_private); inode_dio_done(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); if (bh->b_end_io) bh->b_end_io(bh, 1); return error; } static int do_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; 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); } error = dax_insert_mapping(inode, &bh, vma, vmf); 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) { 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); if (vmf->flags & FAULT_FLAG_WRITE) sb_end_pagefault(sb); return result; } EXPORT_SYMBOL_GPL(dax_fault); /** * 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);