/* * fs/dax.c - Direct Access filesystem code * Copyright (c) 2013-2014 Intel Corporation * Author: Matthew Wilcox * Author: Ross Zwisler * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define RADIX_DAX_MASK 0xf #define RADIX_DAX_SHIFT 4 #define RADIX_DAX_PTE (0x4 | RADIX_TREE_EXCEPTIONAL_ENTRY) #define RADIX_DAX_PMD (0x8 | RADIX_TREE_EXCEPTIONAL_ENTRY) #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK) #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT)) #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \ RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE))) 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); } struct page *read_dax_sector(struct block_device *bdev, sector_t n) { struct page *page = alloc_pages(GFP_KERNEL, 0); struct blk_dax_ctl dax = { .size = PAGE_SIZE, .sector = n & ~((((int) PAGE_SIZE) / 512) - 1), }; long rc; if (!page) return ERR_PTR(-ENOMEM); rc = dax_map_atomic(bdev, &dax); if (rc < 0) return ERR_PTR(rc); memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE); dax_unmap_atomic(bdev, &dax); return page; } /* * dax_clear_sectors() 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_sectors(struct block_device *bdev, sector_t _sector, long _size) { struct blk_dax_ctl dax = { .sector = _sector, .size = _size, }; might_sleep(); do { long count, sz; count = dax_map_atomic(bdev, &dax); if (count < 0) return count; sz = min_t(long, count, SZ_128K); clear_pmem(dax.addr, sz); dax.size -= sz; dax.sector += sz / 512; dax_unmap_atomic(bdev, &dax); cond_resched(); } while (dax.size); wmb_pmem(); return 0; } EXPORT_SYMBOL_GPL(dax_clear_sectors); /* 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) { loff_t final = end - pos + first; /* The final byte of the buffer */ if (first > 0) clear_pmem(addr, first); if (final < size) clear_pmem(addr + final, 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 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, 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) { size_t len; if (pos == max) { unsigned blkbits = inode->i_blkbits; 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; 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)); 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; } if (buffer_unwritten(bh) || buffer_new(bh)) { dax_new_buf(dax.addr, map_len, first, pos, end); need_wmb = true; } dax.addr += first; size = map_len - first; } max = min(pos + size, end); } if (iov_iter_rw(iter) == WRITE) { len = copy_from_iter_pmem(dax.addr, max - pos, iter); need_wmb = true; } 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; } if (need_wmb) wmb_pmem(); 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 * @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)); bh.b_bdev = inode->i_sb->s_bdev; if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) { struct address_space *mapping = inode->i_mapping; inode_lock(inode); retval = filemap_write_and_wait_range(mapping, pos, end - 1); if (retval) { inode_unlock(inode); goto out; } } /* 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); 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); put_page(page); return VM_FAULT_SIGBUS; } vmf->page = page; return VM_FAULT_LOCKED; } static int copy_user_bh(struct page *to, struct inode *inode, struct buffer_head *bh, unsigned long vaddr) { 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_map_atomic(bdev, &dax) < 0) return PTR_ERR(dax.addr); vto = kmap_atomic(to); copy_user_page(vto, (void __force *)dax.addr, vaddr, to); kunmap_atomic(vto); dax_unmap_atomic(bdev, &dax); return 0; } #define NO_SECTOR -1 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT)) static int dax_radix_entry(struct address_space *mapping, pgoff_t index, sector_t sector, bool pmd_entry, bool dirty) { struct radix_tree_root *page_tree = &mapping->page_tree; pgoff_t pmd_index = DAX_PMD_INDEX(index); int type, error = 0; void *entry; WARN_ON_ONCE(pmd_entry && !dirty); if (dirty) __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); spin_lock_irq(&mapping->tree_lock); entry = radix_tree_lookup(page_tree, pmd_index); if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) { index = pmd_index; goto dirty; } entry = radix_tree_lookup(page_tree, index); if (entry) { type = RADIX_DAX_TYPE(entry); if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { error = -EIO; goto unlock; } if (!pmd_entry || type == RADIX_DAX_PMD) goto dirty; /* * We only insert dirty PMD entries into the radix tree. This * means we don't need to worry about removing a dirty PTE * entry and inserting a clean PMD entry, thus reducing the * range we would flush with a follow-up fsync/msync call. */ radix_tree_delete(&mapping->page_tree, index); mapping->nrexceptional--; } if (sector == NO_SECTOR) { /* * This can happen during correct operation if our pfn_mkwrite * fault raced against a hole punch operation. If this * happens the pte that was hole punched will have been * unmapped and the radix tree entry will have been removed by * the time we are called, but the call will still happen. We * will return all the way up to wp_pfn_shared(), where the * pte_same() check will fail, eventually causing page fault * to be retried by the CPU. */ goto unlock; } error = radix_tree_insert(page_tree, index, RADIX_DAX_ENTRY(sector, pmd_entry)); if (error) goto unlock; mapping->nrexceptional++; dirty: if (dirty) radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY); unlock: spin_unlock_irq(&mapping->tree_lock); return error; } static int dax_writeback_one(struct block_device *bdev, struct address_space *mapping, pgoff_t index, void *entry) { struct radix_tree_root *page_tree = &mapping->page_tree; int type = RADIX_DAX_TYPE(entry); struct radix_tree_node *node; struct blk_dax_ctl dax; void **slot; int ret = 0; spin_lock_irq(&mapping->tree_lock); /* * Regular page slots are stabilized by the page lock even * without the tree itself locked. These unlocked entries * need verification under the tree lock. */ if (!__radix_tree_lookup(page_tree, index, &node, &slot)) goto unlock; if (*slot != entry) goto unlock; /* another fsync thread may have already written back this entry */ if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) goto unlock; if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { ret = -EIO; goto unlock; } dax.sector = RADIX_DAX_SECTOR(entry); dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE); spin_unlock_irq(&mapping->tree_lock); /* * We cannot hold tree_lock while calling dax_map_atomic() because it * eventually calls cond_resched(). */ ret = dax_map_atomic(bdev, &dax); if (ret < 0) return ret; if (WARN_ON_ONCE(ret < dax.size)) { ret = -EIO; goto unmap; } wb_cache_pmem(dax.addr, dax.size); spin_lock_irq(&mapping->tree_lock); radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); spin_unlock_irq(&mapping->tree_lock); unmap: dax_unmap_atomic(bdev, &dax); return ret; unlock: spin_unlock_irq(&mapping->tree_lock); return ret; } /* * Flush the mapping to the persistent domain within the byte range of [start, * end]. This is required by data integrity operations to ensure file data is * on persistent storage prior to completion of the operation. */ int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc) { struct inode *inode = mapping->host; pgoff_t start_index, end_index, pmd_index; pgoff_t indices[PAGEVEC_SIZE]; struct pagevec pvec; bool done = false; int i, ret = 0; void *entry; if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) return -EIO; if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL) return 0; start_index = wbc->range_start >> PAGE_SHIFT; end_index = wbc->range_end >> PAGE_SHIFT; pmd_index = DAX_PMD_INDEX(start_index); rcu_read_lock(); entry = radix_tree_lookup(&mapping->page_tree, pmd_index); rcu_read_unlock(); /* see if the start of our range is covered by a PMD entry */ if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) start_index = pmd_index; tag_pages_for_writeback(mapping, start_index, end_index); pagevec_init(&pvec, 0); while (!done) { pvec.nr = find_get_entries_tag(mapping, start_index, PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE, pvec.pages, indices); if (pvec.nr == 0) break; for (i = 0; i < pvec.nr; i++) { if (indices[i] > end_index) { done = true; break; } ret = dax_writeback_one(bdev, mapping, indices[i], pvec.pages[i]); if (ret < 0) return ret; } } wmb_pmem(); return 0; } EXPORT_SYMBOL_GPL(dax_writeback_mapping_range); static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, struct vm_area_struct *vma, struct vm_fault *vmf) { unsigned long vaddr = (unsigned long)vmf->virtual_address; 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; 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; } if (dax_map_atomic(bdev, &dax) < 0) { error = PTR_ERR(dax.addr); goto out; } dax_unmap_atomic(bdev, &dax); error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false, vmf->flags & FAULT_FLAG_WRITE); if (error) goto out; error = vm_insert_mixed(vma, vaddr, dax.pfn); out: i_mmap_unlock_read(mapping); return error; } /** * __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; 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_bdev = inode->i_sb->s_bdev; 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)) { put_page(page); return VM_FAULT_RETRY; } if (unlikely(page->mapping != mapping)) { unlock_page(page); put_page(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) && !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, inode, &bh, 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_SIZE, 0); delete_from_page_cache(page); unlock_page(page); put_page(page); page = NULL; } /* Filesystem should not return unwritten buffers to us! */ WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh)); 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); put_page(page); } goto out; } EXPORT_SYMBOL(__dax_fault); /** * 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 = __dax_fault(vma, vmf, get_block); if (vmf->flags & FAULT_FLAG_WRITE) sb_end_pagefault(sb); return result; } EXPORT_SYMBOL_GPL(dax_fault); #ifdef CONFIG_TRANSPARENT_HUGEPAGE /* * The 'colour' (ie low bits) within a PMD of a page offset. This comes up * more often than one might expect in the below function. */ #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) static void __dax_dbg(struct buffer_head *bh, unsigned long address, const char *reason, const char *fn) { if (bh) { char bname[BDEVNAME_SIZE]; bdevname(bh->b_bdev, bname); pr_debug("%s: %s addr: %lx dev %s state %lx start %lld " "length %zd fallback: %s\n", fn, current->comm, address, bname, bh->b_state, (u64)bh->b_blocknr, bh->b_size, reason); } else { pr_debug("%s: %s addr: %lx fallback: %s\n", fn, current->comm, address, reason); } } #define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd") int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags, get_block_t get_block) { struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; struct buffer_head bh; unsigned blkbits = inode->i_blkbits; unsigned long pmd_addr = address & PMD_MASK; bool write = flags & FAULT_FLAG_WRITE; struct block_device *bdev; pgoff_t size, pgoff; sector_t block; int error, result = 0; bool alloc = false; /* dax pmd mappings require pfn_t_devmap() */ if (!IS_ENABLED(CONFIG_FS_DAX_PMD)) return VM_FAULT_FALLBACK; /* Fall back to PTEs if we're going to COW */ if (write && !(vma->vm_flags & VM_SHARED)) { split_huge_pmd(vma, pmd, address); dax_pmd_dbg(NULL, address, "cow write"); return VM_FAULT_FALLBACK; } /* If the PMD would extend outside the VMA */ if (pmd_addr < vma->vm_start) { dax_pmd_dbg(NULL, address, "vma start unaligned"); return VM_FAULT_FALLBACK; } if ((pmd_addr + PMD_SIZE) > vma->vm_end) { dax_pmd_dbg(NULL, address, "vma end unaligned"); return VM_FAULT_FALLBACK; } pgoff = linear_page_index(vma, pmd_addr); size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; if (pgoff >= size) return VM_FAULT_SIGBUS; /* If the PMD would cover blocks out of the file */ if ((pgoff | PG_PMD_COLOUR) >= size) { dax_pmd_dbg(NULL, address, "offset + huge page size > file size"); return VM_FAULT_FALLBACK; } memset(&bh, 0, sizeof(bh)); bh.b_bdev = inode->i_sb->s_bdev; block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); bh.b_size = PMD_SIZE; if (get_block(inode, block, &bh, 0) != 0) return VM_FAULT_SIGBUS; if (!buffer_mapped(&bh) && write) { if (get_block(inode, block, &bh, 1) != 0) return VM_FAULT_SIGBUS; alloc = true; WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh)); } bdev = bh.b_bdev; /* * If the filesystem isn't willing to tell us the length of a hole, * just fall back to PTEs. Calling get_block 512 times in a loop * would be silly. */ if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) { dax_pmd_dbg(&bh, address, "allocated block too small"); return VM_FAULT_FALLBACK; } /* * If we allocated new storage, make sure no process has any * zero pages covering this hole */ if (alloc) { loff_t lstart = pgoff << PAGE_SHIFT; loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */ truncate_pagecache_range(inode, lstart, lend); } i_mmap_lock_read(mapping); /* * If a truncate happened while we were allocating blocks, we may * leave blocks allocated to the file that are beyond EOF. We can't * take i_mutex here, so just leave them hanging; they'll be freed * when the file is deleted. */ size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; if (pgoff >= size) { result = VM_FAULT_SIGBUS; goto out; } if ((pgoff | PG_PMD_COLOUR) >= size) { dax_pmd_dbg(&bh, address, "offset + huge page size > file size"); goto fallback; } if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) { spinlock_t *ptl; pmd_t entry; struct page *zero_page = get_huge_zero_page(); if (unlikely(!zero_page)) { dax_pmd_dbg(&bh, address, "no zero page"); goto fallback; } ptl = pmd_lock(vma->vm_mm, pmd); if (!pmd_none(*pmd)) { spin_unlock(ptl); dax_pmd_dbg(&bh, address, "pmd already present"); goto fallback; } dev_dbg(part_to_dev(bdev->bd_part), "%s: %s addr: %lx pfn: sect: %llx\n", __func__, current->comm, address, (unsigned long long) to_sector(&bh, inode)); entry = mk_pmd(zero_page, vma->vm_page_prot); entry = pmd_mkhuge(entry); set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry); result = VM_FAULT_NOPAGE; spin_unlock(ptl); } else { 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) { dax_pmd_dbg(&bh, address, "dax-length too small"); dax_unmap_atomic(bdev, &dax); goto fallback; } if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) { dax_pmd_dbg(&bh, address, "pfn unaligned"); dax_unmap_atomic(bdev, &dax); goto fallback; } if (!pfn_t_devmap(dax.pfn)) { dax_unmap_atomic(bdev, &dax); dax_pmd_dbg(&bh, address, "pfn not in memmap"); goto fallback; } dax_unmap_atomic(bdev, &dax); /* * For PTE faults we insert a radix tree entry for reads, and * leave it clean. Then on the first write we dirty the radix * tree entry via the dax_pfn_mkwrite() path. This sequence * allows the dax_pfn_mkwrite() call to be simpler and avoid a * call into get_block() to translate the pgoff to a sector in * order to be able to create a new radix tree entry. * * The PMD path doesn't have an equivalent to * dax_pfn_mkwrite(), though, so for a read followed by a * write we traverse all the way through __dax_pmd_fault() * twice. This means we can just skip inserting a radix tree * entry completely on the initial read and just wait until * the write to insert a dirty entry. */ if (write) { error = dax_radix_entry(mapping, pgoff, dax.sector, true, true); if (error) { dax_pmd_dbg(&bh, address, "PMD radix insertion failed"); goto fallback; } } dev_dbg(part_to_dev(bdev->bd_part), "%s: %s addr: %lx pfn: %lx sect: %llx\n", __func__, current->comm, address, pfn_t_to_pfn(dax.pfn), (unsigned long long) dax.sector); result |= vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write); } out: i_mmap_unlock_read(mapping); return result; fallback: count_vm_event(THP_FAULT_FALLBACK); result = VM_FAULT_FALLBACK; goto out; } EXPORT_SYMBOL_GPL(__dax_pmd_fault); /** * dax_pmd_fault - handle a PMD 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 * pmd_fault handler for DAX files. */ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags, get_block_t get_block) { int result; struct super_block *sb = file_inode(vma->vm_file)->i_sb; if (flags & FAULT_FLAG_WRITE) { sb_start_pagefault(sb); file_update_time(vma->vm_file); } result = __dax_pmd_fault(vma, address, pmd, flags, get_block); if (flags & FAULT_FLAG_WRITE) sb_end_pagefault(sb); return result; } EXPORT_SYMBOL_GPL(dax_pmd_fault); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ /** * 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 file *file = vma->vm_file; int error; /* * We pass NO_SECTOR to dax_radix_entry() because we expect that a * RADIX_DAX_PTE entry already exists in the radix tree from a * previous call to __dax_fault(). We just want to look up that PTE * entry using vmf->pgoff and make sure the dirty tag is set. This * saves us from having to make a call to get_block() here to look * up the sector. */ error = dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false, true); if (error == -ENOMEM) return VM_FAULT_OOM; if (error) return VM_FAULT_SIGBUS; 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_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_SHIFT; unsigned offset = from & (PAGE_SIZE-1); int err; /* Block boundary? Nothing to do */ if (!length) return 0; BUG_ON((offset + length) > PAGE_SIZE); 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) return err; if (buffer_written(&bh)) { struct block_device *bdev = bh.b_bdev; struct blk_dax_ctl dax = { .sector = to_sector(&bh, inode), .size = PAGE_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; } 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_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_ALIGN(from) - from; return dax_zero_page_range(inode, from, length, get_block); } EXPORT_SYMBOL_GPL(dax_truncate_page);