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fs: introduce iomap infrastructure
Add infrastructure for multipage buffered writes. This is implemented using an main iterator that applies an actor function to a range that can be written. This infrastucture is used to implement a buffered write helper, one to zero file ranges and one to implement the ->page_mkwrite VM operations. All of them borrow a fair amount of code from fs/buffers. for now by using an internal version of __block_write_begin that gets passed an iomap and builds the corresponding buffer head. The file system is gets a set of paired ->iomap_begin and ->iomap_end calls which allow it to map/reserve a range and get a notification once the write code is finished with it. Based on earlier code from Dave Chinner. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig
Dave Chinner
parent
199a31c6d9
commit
ae259a9c85
@ -10,6 +10,9 @@ config DCACHE_WORD_ACCESS
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if BLOCK
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config FS_IOMAP
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bool
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source "fs/ext2/Kconfig"
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source "fs/ext4/Kconfig"
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source "fs/jbd2/Kconfig"
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@ -49,6 +49,7 @@ obj-$(CONFIG_COREDUMP) += coredump.o
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obj-$(CONFIG_SYSCTL) += drop_caches.o
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obj-$(CONFIG_FHANDLE) += fhandle.o
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obj-$(CONFIG_FS_IOMAP) += iomap.o
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obj-y += quota/
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70
fs/buffer.c
70
fs/buffer.c
@ -21,6 +21,7 @@
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#include <linux/kernel.h>
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#include <linux/syscalls.h>
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#include <linux/fs.h>
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#include <linux/iomap.h>
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#include <linux/mm.h>
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#include <linux/percpu.h>
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#include <linux/slab.h>
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@ -1891,8 +1892,62 @@ void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
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}
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EXPORT_SYMBOL(page_zero_new_buffers);
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int __block_write_begin(struct page *page, loff_t pos, unsigned len,
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get_block_t *get_block)
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static void
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iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
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struct iomap *iomap)
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{
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loff_t offset = block << inode->i_blkbits;
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bh->b_bdev = iomap->bdev;
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/*
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* Block points to offset in file we need to map, iomap contains
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* the offset at which the map starts. If the map ends before the
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* current block, then do not map the buffer and let the caller
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* handle it.
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*/
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BUG_ON(offset >= iomap->offset + iomap->length);
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switch (iomap->type) {
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case IOMAP_HOLE:
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/*
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* If the buffer is not up to date or beyond the current EOF,
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* we need to mark it as new to ensure sub-block zeroing is
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* executed if necessary.
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*/
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if (!buffer_uptodate(bh) ||
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(offset >= i_size_read(inode)))
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set_buffer_new(bh);
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break;
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case IOMAP_DELALLOC:
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if (!buffer_uptodate(bh) ||
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(offset >= i_size_read(inode)))
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set_buffer_new(bh);
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set_buffer_uptodate(bh);
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set_buffer_mapped(bh);
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set_buffer_delay(bh);
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break;
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case IOMAP_UNWRITTEN:
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/*
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* For unwritten regions, we always need to ensure that
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* sub-block writes cause the regions in the block we are not
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* writing to are zeroed. Set the buffer as new to ensure this.
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*/
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set_buffer_new(bh);
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set_buffer_unwritten(bh);
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/* FALLTHRU */
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case IOMAP_MAPPED:
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if (offset >= i_size_read(inode))
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set_buffer_new(bh);
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bh->b_blocknr = (iomap->blkno >> (inode->i_blkbits - 9)) +
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((offset - iomap->offset) >> inode->i_blkbits);
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set_buffer_mapped(bh);
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break;
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}
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}
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int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
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get_block_t *get_block, struct iomap *iomap)
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{
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unsigned from = pos & (PAGE_SIZE - 1);
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unsigned to = from + len;
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@ -1928,9 +1983,14 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len,
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clear_buffer_new(bh);
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if (!buffer_mapped(bh)) {
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WARN_ON(bh->b_size != blocksize);
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if (get_block) {
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err = get_block(inode, block, bh, 1);
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if (err)
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break;
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} else {
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iomap_to_bh(inode, block, bh, iomap);
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}
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if (buffer_new(bh)) {
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unmap_underlying_metadata(bh->b_bdev,
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bh->b_blocknr);
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@ -1971,6 +2031,12 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len,
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page_zero_new_buffers(page, from, to);
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return err;
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}
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int __block_write_begin(struct page *page, loff_t pos, unsigned len,
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get_block_t *get_block)
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{
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return __block_write_begin_int(page, pos, len, get_block, NULL);
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}
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EXPORT_SYMBOL(__block_write_begin);
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static int __block_commit_write(struct inode *inode, struct page *page,
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@ -11,6 +11,7 @@
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struct super_block;
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struct file_system_type;
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struct iomap;
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struct linux_binprm;
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struct path;
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struct mount;
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@ -39,6 +40,8 @@ static inline int __sync_blockdev(struct block_device *bdev, int wait)
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* buffer.c
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*/
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extern void guard_bio_eod(int rw, struct bio *bio);
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extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
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get_block_t *get_block, struct iomap *iomap);
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/*
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* char_dev.c
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394
fs/iomap.c
Normal file
394
fs/iomap.c
Normal file
@ -0,0 +1,394 @@
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/*
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* Copyright (C) 2010 Red Hat, Inc.
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* Copyright (c) 2016 Christoph Hellwig.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/module.h>
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#include <linux/compiler.h>
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#include <linux/fs.h>
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#include <linux/iomap.h>
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#include <linux/uaccess.h>
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#include <linux/gfp.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/pagemap.h>
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#include <linux/file.h>
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#include <linux/uio.h>
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#include <linux/backing-dev.h>
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#include <linux/buffer_head.h>
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#include "internal.h"
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typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
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void *data, struct iomap *iomap);
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/*
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* Execute a iomap write on a segment of the mapping that spans a
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* contiguous range of pages that have identical block mapping state.
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*
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* This avoids the need to map pages individually, do individual allocations
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* for each page and most importantly avoid the need for filesystem specific
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* locking per page. Instead, all the operations are amortised over the entire
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* range of pages. It is assumed that the filesystems will lock whatever
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* resources they require in the iomap_begin call, and release them in the
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* iomap_end call.
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*/
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static loff_t
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iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
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struct iomap_ops *ops, void *data, iomap_actor_t actor)
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{
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struct iomap iomap = { 0 };
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loff_t written = 0, ret;
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/*
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* Need to map a range from start position for length bytes. This can
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* span multiple pages - it is only guaranteed to return a range of a
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* single type of pages (e.g. all into a hole, all mapped or all
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* unwritten). Failure at this point has nothing to undo.
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*
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* If allocation is required for this range, reserve the space now so
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* that the allocation is guaranteed to succeed later on. Once we copy
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* the data into the page cache pages, then we cannot fail otherwise we
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* expose transient stale data. If the reserve fails, we can safely
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* back out at this point as there is nothing to undo.
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*/
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ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
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if (ret)
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return ret;
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if (WARN_ON(iomap.offset > pos))
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return -EIO;
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/*
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* Cut down the length to the one actually provided by the filesystem,
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* as it might not be able to give us the whole size that we requested.
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*/
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if (iomap.offset + iomap.length < pos + length)
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length = iomap.offset + iomap.length - pos;
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/*
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* Now that we have guaranteed that the space allocation will succeed.
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* we can do the copy-in page by page without having to worry about
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* failures exposing transient data.
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*/
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written = actor(inode, pos, length, data, &iomap);
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/*
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* Now the data has been copied, commit the range we've copied. This
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* should not fail unless the filesystem has had a fatal error.
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*/
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ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0,
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flags, &iomap);
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return written ? written : ret;
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}
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static void
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iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
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{
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loff_t i_size = i_size_read(inode);
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/*
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* Only truncate newly allocated pages beyoned EOF, even if the
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* write started inside the existing inode size.
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*/
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if (pos + len > i_size)
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truncate_pagecache_range(inode, max(pos, i_size), pos + len);
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}
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static int
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iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
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struct page **pagep, struct iomap *iomap)
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{
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pgoff_t index = pos >> PAGE_SHIFT;
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struct page *page;
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int status = 0;
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BUG_ON(pos + len > iomap->offset + iomap->length);
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page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
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if (!page)
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return -ENOMEM;
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status = __block_write_begin_int(page, pos, len, NULL, iomap);
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if (unlikely(status)) {
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unlock_page(page);
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put_page(page);
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page = NULL;
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iomap_write_failed(inode, pos, len);
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}
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*pagep = page;
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return status;
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}
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static int
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iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
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unsigned copied, struct page *page)
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{
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int ret;
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ret = generic_write_end(NULL, inode->i_mapping, pos, len,
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copied, page, NULL);
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if (ret < len)
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iomap_write_failed(inode, pos, len);
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return ret;
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}
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static loff_t
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iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
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struct iomap *iomap)
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{
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struct iov_iter *i = data;
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long status = 0;
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ssize_t written = 0;
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unsigned int flags = AOP_FLAG_NOFS;
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/*
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* Copies from kernel address space cannot fail (NFSD is a big user).
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*/
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if (!iter_is_iovec(i))
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flags |= AOP_FLAG_UNINTERRUPTIBLE;
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do {
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struct page *page;
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unsigned long offset; /* Offset into pagecache page */
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unsigned long bytes; /* Bytes to write to page */
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size_t copied; /* Bytes copied from user */
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offset = (pos & (PAGE_SIZE - 1));
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bytes = min_t(unsigned long, PAGE_SIZE - offset,
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iov_iter_count(i));
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again:
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if (bytes > length)
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bytes = length;
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/*
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* Bring in the user page that we will copy from _first_.
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* Otherwise there's a nasty deadlock on copying from the
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* same page as we're writing to, without it being marked
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* up-to-date.
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*
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* Not only is this an optimisation, but it is also required
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* to check that the address is actually valid, when atomic
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* usercopies are used, below.
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*/
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if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
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status = -EFAULT;
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break;
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}
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status = iomap_write_begin(inode, pos, bytes, flags, &page,
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iomap);
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if (unlikely(status))
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break;
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if (mapping_writably_mapped(inode->i_mapping))
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flush_dcache_page(page);
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pagefault_disable();
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copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
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pagefault_enable();
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flush_dcache_page(page);
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mark_page_accessed(page);
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status = iomap_write_end(inode, pos, bytes, copied, page);
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if (unlikely(status < 0))
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break;
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copied = status;
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cond_resched();
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iov_iter_advance(i, copied);
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if (unlikely(copied == 0)) {
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/*
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* If we were unable to copy any data at all, we must
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* fall back to a single segment length write.
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*
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* If we didn't fallback here, we could livelock
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* because not all segments in the iov can be copied at
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* once without a pagefault.
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*/
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bytes = min_t(unsigned long, PAGE_SIZE - offset,
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iov_iter_single_seg_count(i));
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goto again;
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}
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pos += copied;
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written += copied;
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length -= copied;
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balance_dirty_pages_ratelimited(inode->i_mapping);
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} while (iov_iter_count(i) && length);
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return written ? written : status;
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}
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ssize_t
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iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
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struct iomap_ops *ops)
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{
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struct inode *inode = iocb->ki_filp->f_mapping->host;
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loff_t pos = iocb->ki_pos, ret = 0, written = 0;
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while (iov_iter_count(iter)) {
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ret = iomap_apply(inode, pos, iov_iter_count(iter),
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IOMAP_WRITE, ops, iter, iomap_write_actor);
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if (ret <= 0)
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break;
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pos += ret;
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written += ret;
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}
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return written ? written : ret;
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}
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EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
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static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
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unsigned bytes, struct iomap *iomap)
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{
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struct page *page;
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int status;
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status = iomap_write_begin(inode, pos, bytes,
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AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
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if (status)
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return status;
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zero_user(page, offset, bytes);
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mark_page_accessed(page);
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return iomap_write_end(inode, pos, bytes, bytes, page);
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}
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static loff_t
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iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
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void *data, struct iomap *iomap)
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{
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bool *did_zero = data;
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loff_t written = 0;
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int status;
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/* already zeroed? we're done. */
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if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
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return count;
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do {
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unsigned offset, bytes;
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offset = pos & (PAGE_SIZE - 1); /* Within page */
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bytes = min_t(unsigned, PAGE_SIZE - offset, count);
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status = iomap_zero(inode, pos, offset, bytes, iomap);
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if (status < 0)
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return status;
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pos += bytes;
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count -= bytes;
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written += bytes;
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if (did_zero)
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*did_zero = true;
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} while (count > 0);
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return written;
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}
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int
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iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
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struct iomap_ops *ops)
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{
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loff_t ret;
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while (len > 0) {
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ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
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ops, did_zero, iomap_zero_range_actor);
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if (ret <= 0)
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return ret;
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pos += ret;
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len -= ret;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(iomap_zero_range);
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int
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iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
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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);
|
||||
@ -3,19 +3,65 @@
|
||||
|
||||
#include <linux/types.h>
|
||||
|
||||
/* types of block ranges for multipage write mappings. */
|
||||
struct inode;
|
||||
struct iov_iter;
|
||||
struct kiocb;
|
||||
struct vm_area_struct;
|
||||
struct vm_fault;
|
||||
|
||||
/*
|
||||
* Types of block ranges for iomap mappings:
|
||||
*/
|
||||
#define IOMAP_HOLE 0x01 /* no blocks allocated, need allocation */
|
||||
#define IOMAP_DELALLOC 0x02 /* delayed allocation blocks */
|
||||
#define IOMAP_MAPPED 0x03 /* blocks allocated @blkno */
|
||||
#define IOMAP_UNWRITTEN 0x04 /* blocks allocated @blkno in unwritten state */
|
||||
|
||||
/*
|
||||
* Magic value for blkno:
|
||||
*/
|
||||
#define IOMAP_NULL_BLOCK -1LL /* blkno is not valid */
|
||||
|
||||
struct iomap {
|
||||
sector_t blkno; /* first sector of mapping */
|
||||
sector_t blkno; /* 1st sector of mapping, 512b units */
|
||||
loff_t offset; /* file offset of mapping, bytes */
|
||||
u64 length; /* length of mapping, bytes */
|
||||
int type; /* type of mapping */
|
||||
struct block_device *bdev; /* block device for I/O */
|
||||
};
|
||||
|
||||
/*
|
||||
* Flags for iomap_begin / iomap_end. No flag implies a read.
|
||||
*/
|
||||
#define IOMAP_WRITE (1 << 0)
|
||||
#define IOMAP_ZERO (1 << 1)
|
||||
|
||||
struct iomap_ops {
|
||||
/*
|
||||
* Return the existing mapping at pos, or reserve space starting at
|
||||
* pos for up to length, as long as we can do it as a single mapping.
|
||||
* The actual length is returned in iomap->length.
|
||||
*/
|
||||
int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
|
||||
unsigned flags, struct iomap *iomap);
|
||||
|
||||
/*
|
||||
* Commit and/or unreserve space previous allocated using iomap_begin.
|
||||
* Written indicates the length of the successful write operation which
|
||||
* needs to be commited, while the rest needs to be unreserved.
|
||||
* Written might be zero if no data was written.
|
||||
*/
|
||||
int (*iomap_end)(struct inode *inode, loff_t pos, loff_t length,
|
||||
ssize_t written, unsigned flags, struct iomap *iomap);
|
||||
};
|
||||
|
||||
ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
|
||||
struct iomap_ops *ops);
|
||||
int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
|
||||
bool *did_zero, struct iomap_ops *ops);
|
||||
int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
|
||||
struct iomap_ops *ops);
|
||||
int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
|
||||
struct iomap_ops *ops);
|
||||
|
||||
#endif /* LINUX_IOMAP_H */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user