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- /*
- * 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);
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