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-rw-r--r--fs/dax.c534
1 files changed, 534 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c
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+++ b/fs/dax.c
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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/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);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.