diff options
Diffstat (limited to 'fs/dax.c')
| -rw-r--r-- | fs/dax.c | 787 |
1 files changed, 787 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c new file mode 100644 index 000000000000..43671b68220e --- /dev/null +++ b/fs/dax.c @@ -0,0 +1,787 @@ +/* + * 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/dax.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/pmem.h> +#include <linux/sched.h> +#include <linux/uio.h> +#include <linux/vmstat.h> + +/* + * 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) +{ + struct block_device *bdev = inode->i_sb->s_bdev; + sector_t sector = block << (inode->i_blkbits - 9); + + might_sleep(); + do { + void __pmem *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; + clear_pmem(addr, pgsz); + addr += pgsz; + size -= pgsz; + count -= pgsz; + BUG_ON(pgsz & 511); + sector += pgsz / 512; + cond_resched(); + } + } while (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) +{ + 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 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) + 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; + 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); + need_wmb = true; + } + addr += first; + size = retval - first; + } + max = min(pos + size, end); + } + + if (iov_iter_rw(iter) == WRITE) { + len = copy_from_iter_pmem(addr, max - pos, iter); + need_wmb = true; + } else if (!hole) + len = copy_to_iter((void __force *)addr, max - pos, + iter); + else + len = iov_iter_zero(max - pos, iter); + + if (!len) { + retval = -EFAULT; + break; + } + + pos += len; + addr += len; + } + + if (need_wmb) + wmb_pmem(); + + 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 */ + 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) + mutex_unlock(&inode->i_mutex); + + if ((retval > 0) && end_io) + end_io(iocb, pos, retval, bh.b_private); + + 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); + 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 __pmem *vfrom; + void *vto; + + if (dax_get_addr(bh, &vfrom, blkbits) < 0) + return -EIO; + vto = kmap_atomic(to); + copy_user_page(vto, (void __force *)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 __pmem *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_pmem(addr, PAGE_SIZE); + wmb_pmem(); + } + + error = vm_insert_mixed(vma, vaddr, 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 + * @complete_unwritten: The filesystem method used to convert unwritten blocks + * to written so the data written to them is exposed. This is required for + * required by write faults for filesystems that will return unwritten + * extent mappings from @get_block, but it is optional for reads as + * dax_insert_mapping() will always zero unwritten blocks. If the fs does + * not support unwritten extents, the it should pass NULL. + * + * 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, 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)) { + if (complete_unwritten) + complete_unwritten(&bh, !error); + else + WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE)); + } + + 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; +} +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, 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 = __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); + +#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) + +int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, unsigned int flags, 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 buffer_head bh; + unsigned blkbits = inode->i_blkbits; + unsigned long pmd_addr = address & PMD_MASK; + bool write = flags & FAULT_FLAG_WRITE; + long length; + void __pmem *kaddr; + pgoff_t size, pgoff; + sector_t block, sector; + unsigned long pfn; + int result = 0; + + /* dax pmd mappings are broken wrt gup and fork */ + 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)) + return VM_FAULT_FALLBACK; + /* If the PMD would extend outside the VMA */ + if (pmd_addr < vma->vm_start) + return VM_FAULT_FALLBACK; + if ((pmd_addr + PMD_SIZE) > vma->vm_end) + 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) + return VM_FAULT_FALLBACK; + + memset(&bh, 0, sizeof(bh)); + block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); + + bh.b_size = PMD_SIZE; + length = get_block(inode, block, &bh, write); + if (length) + return VM_FAULT_SIGBUS; + i_mmap_lock_read(mapping); + + /* + * 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) + goto fallback; + + /* + * If we allocated new storage, make sure no process has any + * zero pages covering this hole + */ + if (buffer_new(&bh)) { + i_mmap_unlock_read(mapping); + unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0); + 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) + 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)) + goto fallback; + + ptl = pmd_lock(vma->vm_mm, pmd); + if (!pmd_none(*pmd)) { + spin_unlock(ptl); + goto fallback; + } + + 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 { + sector = bh.b_blocknr << (blkbits - 9); + length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, + bh.b_size); + if (length < 0) { + result = VM_FAULT_SIGBUS; + goto out; + } + if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) + goto fallback; + + /* + * TODO: teach vmf_insert_pfn_pmd() to support + * 'pte_special' for pmds + */ + if (pfn_valid(pfn)) + goto fallback; + + if (buffer_unwritten(&bh) || buffer_new(&bh)) { + int i; + for (i = 0; i < PTRS_PER_PMD; i++) + clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE); + wmb_pmem(); + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + result |= VM_FAULT_MAJOR; + } + + result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write); + } + + out: + i_mmap_unlock_read(mapping); + + if (buffer_unwritten(&bh)) + complete_unwritten(&bh, !(result & VM_FAULT_ERROR)); + + 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, + dax_iodone_t complete_unwritten) +{ + 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, + complete_unwritten); + 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 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 __pmem *addr; + err = dax_get_addr(&bh, &addr, inode->i_blkbits); + if (err < 0) + return err; + clear_pmem(addr + offset, length); + wmb_pmem(); + } + + 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); |