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![Christoph Hellwig](/assets/img/avatar_default.png)
[ Upstream commit 49694d14ff
]
The length variable is rather pointless given that it can be trivially
deduced from offset and size. Also the initial calculation can lead
to KASAN warnings.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Leizhen (ThunderTown) <thunder.leizhen@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
205 lines
4.6 KiB
C
205 lines
4.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2017 Red Hat, Inc.
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* Copyright (c) 2018 Christoph Hellwig.
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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/pagemap.h>
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#include <linux/pagevec.h>
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/*
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* Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
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* Returns true if found and updates @lastoff to the offset in file.
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*/
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static bool
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page_seek_hole_data(struct inode *inode, struct page *page, loff_t *lastoff,
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int whence)
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{
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const struct address_space_operations *ops = inode->i_mapping->a_ops;
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unsigned int bsize = i_blocksize(inode), off;
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bool seek_data = whence == SEEK_DATA;
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loff_t poff = page_offset(page);
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if (WARN_ON_ONCE(*lastoff >= poff + PAGE_SIZE))
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return false;
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if (*lastoff < poff) {
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/*
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* Last offset smaller than the start of the page means we found
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* a hole:
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*/
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if (whence == SEEK_HOLE)
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return true;
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*lastoff = poff;
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}
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/*
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* Just check the page unless we can and should check block ranges:
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*/
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if (bsize == PAGE_SIZE || !ops->is_partially_uptodate)
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return PageUptodate(page) == seek_data;
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lock_page(page);
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if (unlikely(page->mapping != inode->i_mapping))
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goto out_unlock_not_found;
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for (off = 0; off < PAGE_SIZE; off += bsize) {
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if (offset_in_page(*lastoff) >= off + bsize)
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continue;
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if (ops->is_partially_uptodate(page, off, bsize) == seek_data) {
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unlock_page(page);
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return true;
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}
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*lastoff = poff + off + bsize;
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}
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out_unlock_not_found:
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unlock_page(page);
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return false;
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}
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/*
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* Seek for SEEK_DATA / SEEK_HOLE in the page cache.
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*
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* Within unwritten extents, the page cache determines which parts are holes
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* and which are data: uptodate buffer heads count as data; everything else
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* counts as a hole.
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*
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* Returns the resulting offset on successs, and -ENOENT otherwise.
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*/
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static loff_t
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page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
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int whence)
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{
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pgoff_t index = offset >> PAGE_SHIFT;
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pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE);
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loff_t lastoff = offset;
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struct pagevec pvec;
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if (length <= 0)
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return -ENOENT;
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pagevec_init(&pvec);
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do {
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unsigned nr_pages, i;
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nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
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end - 1);
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if (nr_pages == 0)
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break;
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for (i = 0; i < nr_pages; i++) {
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struct page *page = pvec.pages[i];
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if (page_seek_hole_data(inode, page, &lastoff, whence))
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goto check_range;
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lastoff = page_offset(page) + PAGE_SIZE;
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}
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pagevec_release(&pvec);
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} while (index < end);
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/* When no page at lastoff and we are not done, we found a hole. */
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if (whence != SEEK_HOLE)
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goto not_found;
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check_range:
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if (lastoff < offset + length)
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goto out;
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not_found:
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lastoff = -ENOENT;
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out:
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pagevec_release(&pvec);
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return lastoff;
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}
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static loff_t
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iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
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void *data, struct iomap *iomap)
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{
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switch (iomap->type) {
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case IOMAP_UNWRITTEN:
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offset = page_cache_seek_hole_data(inode, offset, length,
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SEEK_HOLE);
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if (offset < 0)
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return length;
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/* fall through */
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case IOMAP_HOLE:
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*(loff_t *)data = offset;
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return 0;
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default:
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return length;
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}
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}
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loff_t
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iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
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{
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loff_t size = i_size_read(inode);
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loff_t ret;
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/* Nothing to be found before or beyond the end of the file. */
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if (offset < 0 || offset >= size)
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return -ENXIO;
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while (offset < size) {
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ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
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ops, &offset, iomap_seek_hole_actor);
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if (ret < 0)
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return ret;
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if (ret == 0)
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break;
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offset += ret;
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}
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return offset;
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}
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EXPORT_SYMBOL_GPL(iomap_seek_hole);
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static loff_t
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iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
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void *data, struct iomap *iomap)
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{
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switch (iomap->type) {
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case IOMAP_HOLE:
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return length;
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case IOMAP_UNWRITTEN:
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offset = page_cache_seek_hole_data(inode, offset, length,
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SEEK_DATA);
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if (offset < 0)
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return length;
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/*FALLTHRU*/
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default:
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*(loff_t *)data = offset;
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return 0;
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}
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}
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loff_t
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iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
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{
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loff_t size = i_size_read(inode);
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loff_t ret;
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/* Nothing to be found before or beyond the end of the file. */
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if (offset < 0 || offset >= size)
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return -ENXIO;
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while (offset < size) {
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ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
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ops, &offset, iomap_seek_data_actor);
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if (ret < 0)
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return ret;
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if (ret == 0)
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return offset;
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offset += ret;
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}
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/* We've reached the end of the file without finding data */
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return -ENXIO;
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}
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EXPORT_SYMBOL_GPL(iomap_seek_data);
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