diff options
Diffstat (limited to 'fs/iomap.c')
| -rw-r--r-- | fs/iomap.c | 394 |
1 files changed, 394 insertions, 0 deletions
diff --git a/fs/iomap.c b/fs/iomap.c new file mode 100644 index 000000000000..8e2fc17c266f --- /dev/null +++ b/fs/iomap.c @@ -0,0 +1,394 @@ +/* + * Copyright (C) 2010 Red Hat, Inc. + * Copyright (c) 2016 Christoph Hellwig. + * + * 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/module.h> +#include <linux/compiler.h> +#include <linux/fs.h> +#include <linux/iomap.h> +#include <linux/uaccess.h> +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/pagemap.h> +#include <linux/file.h> +#include <linux/uio.h> +#include <linux/backing-dev.h> +#include <linux/buffer_head.h> +#include "internal.h" + +typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len, + void *data, struct iomap *iomap); + +/* + * Execute a iomap write on a segment of the mapping that spans a + * contiguous range of pages that have identical block mapping state. + * + * This avoids the need to map pages individually, do individual allocations + * for each page and most importantly avoid the need for filesystem specific + * locking per page. Instead, all the operations are amortised over the entire + * range of pages. It is assumed that the filesystems will lock whatever + * resources they require in the iomap_begin call, and release them in the + * iomap_end call. + */ +static loff_t +iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, + struct iomap_ops *ops, void *data, iomap_actor_t actor) +{ + struct iomap iomap = { 0 }; + loff_t written = 0, ret; + + /* + * Need to map a range from start position for length bytes. This can + * span multiple pages - it is only guaranteed to return a range of a + * single type of pages (e.g. all into a hole, all mapped or all + * unwritten). Failure at this point has nothing to undo. + * + * If allocation is required for this range, reserve the space now so + * that the allocation is guaranteed to succeed later on. Once we copy + * the data into the page cache pages, then we cannot fail otherwise we + * expose transient stale data. If the reserve fails, we can safely + * back out at this point as there is nothing to undo. + */ + ret = ops->iomap_begin(inode, pos, length, flags, &iomap); + if (ret) + return ret; + if (WARN_ON(iomap.offset > pos)) + return -EIO; + + /* + * Cut down the length to the one actually provided by the filesystem, + * as it might not be able to give us the whole size that we requested. + */ + if (iomap.offset + iomap.length < pos + length) + length = iomap.offset + iomap.length - pos; + + /* + * Now that we have guaranteed that the space allocation will succeed. + * we can do the copy-in page by page without having to worry about + * failures exposing transient data. + */ + written = actor(inode, pos, length, data, &iomap); + + /* + * Now the data has been copied, commit the range we've copied. This + * should not fail unless the filesystem has had a fatal error. + */ + ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0, + flags, &iomap); + + return written ? written : ret; +} + +static void +iomap_write_failed(struct inode *inode, loff_t pos, unsigned len) +{ + loff_t i_size = i_size_read(inode); + + /* + * Only truncate newly allocated pages beyoned EOF, even if the + * write started inside the existing inode size. + */ + if (pos + len > i_size) + truncate_pagecache_range(inode, max(pos, i_size), pos + len); +} + +static int +iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, + struct page **pagep, struct iomap *iomap) +{ + pgoff_t index = pos >> PAGE_SHIFT; + struct page *page; + int status = 0; + + BUG_ON(pos + len > iomap->offset + iomap->length); + + page = grab_cache_page_write_begin(inode->i_mapping, index, flags); + if (!page) + return -ENOMEM; + + status = __block_write_begin_int(page, pos, len, NULL, iomap); + if (unlikely(status)) { + unlock_page(page); + put_page(page); + page = NULL; + + iomap_write_failed(inode, pos, len); + } + + *pagep = page; + return status; +} + +static int +iomap_write_end(struct inode *inode, loff_t pos, unsigned len, + unsigned copied, struct page *page) +{ + int ret; + + ret = generic_write_end(NULL, inode->i_mapping, pos, len, + copied, page, NULL); + if (ret < len) + iomap_write_failed(inode, pos, len); + return ret; +} + +static loff_t +iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data, + struct iomap *iomap) +{ + struct iov_iter *i = data; + long status = 0; + ssize_t written = 0; + unsigned int flags = AOP_FLAG_NOFS; + + /* + * Copies from kernel address space cannot fail (NFSD is a big user). + */ + if (!iter_is_iovec(i)) + flags |= AOP_FLAG_UNINTERRUPTIBLE; + + do { + struct page *page; + unsigned long offset; /* Offset into pagecache page */ + unsigned long bytes; /* Bytes to write to page */ + size_t copied; /* Bytes copied from user */ + + offset = (pos & (PAGE_SIZE - 1)); + bytes = min_t(unsigned long, PAGE_SIZE - offset, + iov_iter_count(i)); +again: + if (bytes > length) + bytes = length; + + /* + * Bring in the user page that we will copy from _first_. + * Otherwise there's a nasty deadlock on copying from the + * same page as we're writing to, without it being marked + * up-to-date. + * + * Not only is this an optimisation, but it is also required + * to check that the address is actually valid, when atomic + * usercopies are used, below. + */ + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { + status = -EFAULT; + break; + } + + status = iomap_write_begin(inode, pos, bytes, flags, &page, + iomap); + if (unlikely(status)) + break; + + if (mapping_writably_mapped(inode->i_mapping)) + flush_dcache_page(page); + + pagefault_disable(); + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); + pagefault_enable(); + + flush_dcache_page(page); + mark_page_accessed(page); + + status = iomap_write_end(inode, pos, bytes, copied, page); + if (unlikely(status < 0)) + break; + copied = status; + + cond_resched(); + + iov_iter_advance(i, copied); + if (unlikely(copied == 0)) { + /* + * If we were unable to copy any data at all, we must + * fall back to a single segment length write. + * + * If we didn't fallback here, we could livelock + * because not all segments in the iov can be copied at + * once without a pagefault. + */ + bytes = min_t(unsigned long, PAGE_SIZE - offset, + iov_iter_single_seg_count(i)); + goto again; + } + pos += copied; + written += copied; + length -= copied; + + balance_dirty_pages_ratelimited(inode->i_mapping); + } while (iov_iter_count(i) && length); + + return written ? written : status; +} + +ssize_t +iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter, + struct iomap_ops *ops) +{ + struct inode *inode = iocb->ki_filp->f_mapping->host; + loff_t pos = iocb->ki_pos, ret = 0, written = 0; + + while (iov_iter_count(iter)) { + ret = iomap_apply(inode, pos, iov_iter_count(iter), + IOMAP_WRITE, ops, iter, iomap_write_actor); + if (ret <= 0) + break; + pos += ret; + written += ret; + } + + return written ? written : ret; +} +EXPORT_SYMBOL_GPL(iomap_file_buffered_write); + +static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset, + unsigned bytes, struct iomap *iomap) +{ + struct page *page; + int status; + + status = iomap_write_begin(inode, pos, bytes, + AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap); + if (status) + return status; + + zero_user(page, offset, bytes); + mark_page_accessed(page); + + return iomap_write_end(inode, pos, bytes, bytes, page); +} + +static loff_t +iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count, + void *data, struct iomap *iomap) +{ + bool *did_zero = data; + loff_t written = 0; + int status; + + /* already zeroed? we're done. */ + if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN) + return count; + + do { + unsigned offset, bytes; + + offset = pos & (PAGE_SIZE - 1); /* Within page */ + bytes = min_t(unsigned, PAGE_SIZE - offset, count); + + status = iomap_zero(inode, pos, offset, bytes, iomap); + if (status < 0) + return status; + + pos += bytes; + count -= bytes; + written += bytes; + if (did_zero) + *did_zero = true; + } while (count > 0); + + return written; +} + +int +iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, + struct iomap_ops *ops) +{ + loff_t ret; + + while (len > 0) { + ret = iomap_apply(inode, pos, len, IOMAP_ZERO, + ops, did_zero, iomap_zero_range_actor); + if (ret <= 0) + return ret; + + pos += ret; + len -= ret; + } + + return 0; +} +EXPORT_SYMBOL_GPL(iomap_zero_range); + +int +iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, + struct iomap_ops *ops) +{ + unsigned blocksize = (1 << inode->i_blkbits); + unsigned off = pos & (blocksize - 1); + + /* Block boundary? Nothing to do */ + if (!off) + return 0; + return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops); +} +EXPORT_SYMBOL_GPL(iomap_truncate_page); + +static loff_t +iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length, + void *data, struct iomap *iomap) +{ + struct page *page = data; + int ret; + + ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length, + NULL, iomap); + if (ret) + return ret; + + block_commit_write(page, 0, length); + return length; +} + +int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, + struct iomap_ops *ops) +{ + struct page *page = vmf->page; + struct inode *inode = file_inode(vma->vm_file); + unsigned long length; + loff_t offset, size; + ssize_t ret; + + lock_page(page); + size = i_size_read(inode); + if ((page->mapping != inode->i_mapping) || + (page_offset(page) > size)) { + /* We overload EFAULT to mean page got truncated */ + ret = -EFAULT; + goto out_unlock; + } + + /* page is wholly or partially inside EOF */ + if (((page->index + 1) << PAGE_SHIFT) > size) + length = size & ~PAGE_MASK; + else + length = PAGE_SIZE; + + offset = page_offset(page); + while (length > 0) { + ret = iomap_apply(inode, offset, length, IOMAP_WRITE, + ops, page, iomap_page_mkwrite_actor); + if (unlikely(ret <= 0)) + goto out_unlock; + offset += ret; + length -= ret; + } + + set_page_dirty(page); + wait_for_stable_page(page); + return 0; +out_unlock: + unlock_page(page); + return ret; +} +EXPORT_SYMBOL_GPL(iomap_page_mkwrite); |