From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- fs/mpage.c | 670 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 670 insertions(+) create mode 100644 fs/mpage.c (limited to 'fs/mpage.c') diff --git a/fs/mpage.c b/fs/mpage.c new file mode 100644 index 000000000..0f8ae954a --- /dev/null +++ b/fs/mpage.c @@ -0,0 +1,670 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fs/mpage.c + * + * Copyright (C) 2002, Linus Torvalds. + * + * Contains functions related to preparing and submitting BIOs which contain + * multiple pagecache pages. + * + * 15May2002 Andrew Morton + * Initial version + * 27Jun2002 axboe@suse.de + * use bio_add_page() to build bio's just the right size + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "internal.h" + +/* + * I/O completion handler for multipage BIOs. + * + * The mpage code never puts partial pages into a BIO (except for end-of-file). + * If a page does not map to a contiguous run of blocks then it simply falls + * back to block_read_full_folio(). + * + * Why is this? If a page's completion depends on a number of different BIOs + * which can complete in any order (or at the same time) then determining the + * status of that page is hard. See end_buffer_async_read() for the details. + * There is no point in duplicating all that complexity. + */ +static void mpage_end_io(struct bio *bio) +{ + struct bio_vec *bv; + struct bvec_iter_all iter_all; + + bio_for_each_segment_all(bv, bio, iter_all) { + struct page *page = bv->bv_page; + page_endio(page, bio_op(bio), + blk_status_to_errno(bio->bi_status)); + } + + bio_put(bio); +} + +static struct bio *mpage_bio_submit(struct bio *bio) +{ + bio->bi_end_io = mpage_end_io; + guard_bio_eod(bio); + submit_bio(bio); + return NULL; +} + +/* + * support function for mpage_readahead. The fs supplied get_block might + * return an up to date buffer. This is used to map that buffer into + * the page, which allows read_folio to avoid triggering a duplicate call + * to get_block. + * + * The idea is to avoid adding buffers to pages that don't already have + * them. So when the buffer is up to date and the page size == block size, + * this marks the page up to date instead of adding new buffers. + */ +static void map_buffer_to_folio(struct folio *folio, struct buffer_head *bh, + int page_block) +{ + struct inode *inode = folio->mapping->host; + struct buffer_head *page_bh, *head; + int block = 0; + + head = folio_buffers(folio); + if (!head) { + /* + * don't make any buffers if there is only one buffer on + * the folio and the folio just needs to be set up to date + */ + if (inode->i_blkbits == PAGE_SHIFT && + buffer_uptodate(bh)) { + folio_mark_uptodate(folio); + return; + } + create_empty_buffers(&folio->page, i_blocksize(inode), 0); + head = folio_buffers(folio); + } + + page_bh = head; + do { + if (block == page_block) { + page_bh->b_state = bh->b_state; + page_bh->b_bdev = bh->b_bdev; + page_bh->b_blocknr = bh->b_blocknr; + break; + } + page_bh = page_bh->b_this_page; + block++; + } while (page_bh != head); +} + +struct mpage_readpage_args { + struct bio *bio; + struct folio *folio; + unsigned int nr_pages; + bool is_readahead; + sector_t last_block_in_bio; + struct buffer_head map_bh; + unsigned long first_logical_block; + get_block_t *get_block; +}; + +/* + * This is the worker routine which does all the work of mapping the disk + * blocks and constructs largest possible bios, submits them for IO if the + * blocks are not contiguous on the disk. + * + * We pass a buffer_head back and forth and use its buffer_mapped() flag to + * represent the validity of its disk mapping and to decide when to do the next + * get_block() call. + */ +static struct bio *do_mpage_readpage(struct mpage_readpage_args *args) +{ + struct folio *folio = args->folio; + struct inode *inode = folio->mapping->host; + const unsigned blkbits = inode->i_blkbits; + const unsigned blocks_per_page = PAGE_SIZE >> blkbits; + const unsigned blocksize = 1 << blkbits; + struct buffer_head *map_bh = &args->map_bh; + sector_t block_in_file; + sector_t last_block; + sector_t last_block_in_file; + sector_t blocks[MAX_BUF_PER_PAGE]; + unsigned page_block; + unsigned first_hole = blocks_per_page; + struct block_device *bdev = NULL; + int length; + int fully_mapped = 1; + blk_opf_t opf = REQ_OP_READ; + unsigned nblocks; + unsigned relative_block; + gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL); + + /* MAX_BUF_PER_PAGE, for example */ + VM_BUG_ON_FOLIO(folio_test_large(folio), folio); + + if (args->is_readahead) { + opf |= REQ_RAHEAD; + gfp |= __GFP_NORETRY | __GFP_NOWARN; + } + + if (folio_buffers(folio)) + goto confused; + + block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits); + last_block = block_in_file + args->nr_pages * blocks_per_page; + last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; + if (last_block > last_block_in_file) + last_block = last_block_in_file; + page_block = 0; + + /* + * Map blocks using the result from the previous get_blocks call first. + */ + nblocks = map_bh->b_size >> blkbits; + if (buffer_mapped(map_bh) && + block_in_file > args->first_logical_block && + block_in_file < (args->first_logical_block + nblocks)) { + unsigned map_offset = block_in_file - args->first_logical_block; + unsigned last = nblocks - map_offset; + + for (relative_block = 0; ; relative_block++) { + if (relative_block == last) { + clear_buffer_mapped(map_bh); + break; + } + if (page_block == blocks_per_page) + break; + blocks[page_block] = map_bh->b_blocknr + map_offset + + relative_block; + page_block++; + block_in_file++; + } + bdev = map_bh->b_bdev; + } + + /* + * Then do more get_blocks calls until we are done with this folio. + */ + map_bh->b_page = &folio->page; + while (page_block < blocks_per_page) { + map_bh->b_state = 0; + map_bh->b_size = 0; + + if (block_in_file < last_block) { + map_bh->b_size = (last_block-block_in_file) << blkbits; + if (args->get_block(inode, block_in_file, map_bh, 0)) + goto confused; + args->first_logical_block = block_in_file; + } + + if (!buffer_mapped(map_bh)) { + fully_mapped = 0; + if (first_hole == blocks_per_page) + first_hole = page_block; + page_block++; + block_in_file++; + continue; + } + + /* some filesystems will copy data into the page during + * the get_block call, in which case we don't want to + * read it again. map_buffer_to_folio copies the data + * we just collected from get_block into the folio's buffers + * so read_folio doesn't have to repeat the get_block call + */ + if (buffer_uptodate(map_bh)) { + map_buffer_to_folio(folio, map_bh, page_block); + goto confused; + } + + if (first_hole != blocks_per_page) + goto confused; /* hole -> non-hole */ + + /* Contiguous blocks? */ + if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) + goto confused; + nblocks = map_bh->b_size >> blkbits; + for (relative_block = 0; ; relative_block++) { + if (relative_block == nblocks) { + clear_buffer_mapped(map_bh); + break; + } else if (page_block == blocks_per_page) + break; + blocks[page_block] = map_bh->b_blocknr+relative_block; + page_block++; + block_in_file++; + } + bdev = map_bh->b_bdev; + } + + if (first_hole != blocks_per_page) { + folio_zero_segment(folio, first_hole << blkbits, PAGE_SIZE); + if (first_hole == 0) { + folio_mark_uptodate(folio); + folio_unlock(folio); + goto out; + } + } else if (fully_mapped) { + folio_set_mappedtodisk(folio); + } + + /* + * This folio will go to BIO. Do we need to send this BIO off first? + */ + if (args->bio && (args->last_block_in_bio != blocks[0] - 1)) + args->bio = mpage_bio_submit(args->bio); + +alloc_new: + if (args->bio == NULL) { + if (first_hole == blocks_per_page) { + if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9), + &folio->page)) + goto out; + } + args->bio = bio_alloc(bdev, bio_max_segs(args->nr_pages), opf, + gfp); + if (args->bio == NULL) + goto confused; + args->bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); + } + + length = first_hole << blkbits; + if (!bio_add_folio(args->bio, folio, length, 0)) { + args->bio = mpage_bio_submit(args->bio); + goto alloc_new; + } + + relative_block = block_in_file - args->first_logical_block; + nblocks = map_bh->b_size >> blkbits; + if ((buffer_boundary(map_bh) && relative_block == nblocks) || + (first_hole != blocks_per_page)) + args->bio = mpage_bio_submit(args->bio); + else + args->last_block_in_bio = blocks[blocks_per_page - 1]; +out: + return args->bio; + +confused: + if (args->bio) + args->bio = mpage_bio_submit(args->bio); + if (!folio_test_uptodate(folio)) + block_read_full_folio(folio, args->get_block); + else + folio_unlock(folio); + goto out; +} + +/** + * mpage_readahead - start reads against pages + * @rac: Describes which pages to read. + * @get_block: The filesystem's block mapper function. + * + * This function walks the pages and the blocks within each page, building and + * emitting large BIOs. + * + * If anything unusual happens, such as: + * + * - encountering a page which has buffers + * - encountering a page which has a non-hole after a hole + * - encountering a page with non-contiguous blocks + * + * then this code just gives up and calls the buffer_head-based read function. + * It does handle a page which has holes at the end - that is a common case: + * the end-of-file on blocksize < PAGE_SIZE setups. + * + * BH_Boundary explanation: + * + * There is a problem. The mpage read code assembles several pages, gets all + * their disk mappings, and then submits them all. That's fine, but obtaining + * the disk mappings may require I/O. Reads of indirect blocks, for example. + * + * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be + * submitted in the following order: + * + * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 + * + * because the indirect block has to be read to get the mappings of blocks + * 13,14,15,16. Obviously, this impacts performance. + * + * So what we do it to allow the filesystem's get_block() function to set + * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block + * after this one will require I/O against a block which is probably close to + * this one. So you should push what I/O you have currently accumulated. + * + * This all causes the disk requests to be issued in the correct order. + */ +void mpage_readahead(struct readahead_control *rac, get_block_t get_block) +{ + struct folio *folio; + struct mpage_readpage_args args = { + .get_block = get_block, + .is_readahead = true, + }; + + while ((folio = readahead_folio(rac))) { + prefetchw(&folio->flags); + args.folio = folio; + args.nr_pages = readahead_count(rac); + args.bio = do_mpage_readpage(&args); + } + if (args.bio) + mpage_bio_submit(args.bio); +} +EXPORT_SYMBOL(mpage_readahead); + +/* + * This isn't called much at all + */ +int mpage_read_folio(struct folio *folio, get_block_t get_block) +{ + struct mpage_readpage_args args = { + .folio = folio, + .nr_pages = 1, + .get_block = get_block, + }; + + args.bio = do_mpage_readpage(&args); + if (args.bio) + mpage_bio_submit(args.bio); + return 0; +} +EXPORT_SYMBOL(mpage_read_folio); + +/* + * Writing is not so simple. + * + * If the page has buffers then they will be used for obtaining the disk + * mapping. We only support pages which are fully mapped-and-dirty, with a + * special case for pages which are unmapped at the end: end-of-file. + * + * If the page has no buffers (preferred) then the page is mapped here. + * + * If all blocks are found to be contiguous then the page can go into the + * BIO. Otherwise fall back to the mapping's writepage(). + * + * FIXME: This code wants an estimate of how many pages are still to be + * written, so it can intelligently allocate a suitably-sized BIO. For now, + * just allocate full-size (16-page) BIOs. + */ + +struct mpage_data { + struct bio *bio; + sector_t last_block_in_bio; + get_block_t *get_block; +}; + +/* + * We have our BIO, so we can now mark the buffers clean. Make + * sure to only clean buffers which we know we'll be writing. + */ +static void clean_buffers(struct page *page, unsigned first_unmapped) +{ + unsigned buffer_counter = 0; + struct buffer_head *bh, *head; + if (!page_has_buffers(page)) + return; + head = page_buffers(page); + bh = head; + + do { + if (buffer_counter++ == first_unmapped) + break; + clear_buffer_dirty(bh); + bh = bh->b_this_page; + } while (bh != head); + + /* + * we cannot drop the bh if the page is not uptodate or a concurrent + * read_folio would fail to serialize with the bh and it would read from + * disk before we reach the platter. + */ + if (buffer_heads_over_limit && PageUptodate(page)) + try_to_free_buffers(page_folio(page)); +} + +/* + * For situations where we want to clean all buffers attached to a page. + * We don't need to calculate how many buffers are attached to the page, + * we just need to specify a number larger than the maximum number of buffers. + */ +void clean_page_buffers(struct page *page) +{ + clean_buffers(page, ~0U); +} + +static int __mpage_writepage(struct page *page, struct writeback_control *wbc, + void *data) +{ + struct mpage_data *mpd = data; + struct bio *bio = mpd->bio; + struct address_space *mapping = page->mapping; + struct inode *inode = page->mapping->host; + const unsigned blkbits = inode->i_blkbits; + unsigned long end_index; + const unsigned blocks_per_page = PAGE_SIZE >> blkbits; + sector_t last_block; + sector_t block_in_file; + sector_t blocks[MAX_BUF_PER_PAGE]; + unsigned page_block; + unsigned first_unmapped = blocks_per_page; + struct block_device *bdev = NULL; + int boundary = 0; + sector_t boundary_block = 0; + struct block_device *boundary_bdev = NULL; + int length; + struct buffer_head map_bh; + loff_t i_size = i_size_read(inode); + int ret = 0; + + if (page_has_buffers(page)) { + struct buffer_head *head = page_buffers(page); + struct buffer_head *bh = head; + + /* If they're all mapped and dirty, do it */ + page_block = 0; + do { + BUG_ON(buffer_locked(bh)); + if (!buffer_mapped(bh)) { + /* + * unmapped dirty buffers are created by + * block_dirty_folio -> mmapped data + */ + if (buffer_dirty(bh)) + goto confused; + if (first_unmapped == blocks_per_page) + first_unmapped = page_block; + continue; + } + + if (first_unmapped != blocks_per_page) + goto confused; /* hole -> non-hole */ + + if (!buffer_dirty(bh) || !buffer_uptodate(bh)) + goto confused; + if (page_block) { + if (bh->b_blocknr != blocks[page_block-1] + 1) + goto confused; + } + blocks[page_block++] = bh->b_blocknr; + boundary = buffer_boundary(bh); + if (boundary) { + boundary_block = bh->b_blocknr; + boundary_bdev = bh->b_bdev; + } + bdev = bh->b_bdev; + } while ((bh = bh->b_this_page) != head); + + if (first_unmapped) + goto page_is_mapped; + + /* + * Page has buffers, but they are all unmapped. The page was + * created by pagein or read over a hole which was handled by + * block_read_full_folio(). If this address_space is also + * using mpage_readahead then this can rarely happen. + */ + goto confused; + } + + /* + * The page has no buffers: map it to disk + */ + BUG_ON(!PageUptodate(page)); + block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits); + last_block = (i_size - 1) >> blkbits; + map_bh.b_page = page; + for (page_block = 0; page_block < blocks_per_page; ) { + + map_bh.b_state = 0; + map_bh.b_size = 1 << blkbits; + if (mpd->get_block(inode, block_in_file, &map_bh, 1)) + goto confused; + if (buffer_new(&map_bh)) + clean_bdev_bh_alias(&map_bh); + if (buffer_boundary(&map_bh)) { + boundary_block = map_bh.b_blocknr; + boundary_bdev = map_bh.b_bdev; + } + if (page_block) { + if (map_bh.b_blocknr != blocks[page_block-1] + 1) + goto confused; + } + blocks[page_block++] = map_bh.b_blocknr; + boundary = buffer_boundary(&map_bh); + bdev = map_bh.b_bdev; + if (block_in_file == last_block) + break; + block_in_file++; + } + BUG_ON(page_block == 0); + + first_unmapped = page_block; + +page_is_mapped: + end_index = i_size >> PAGE_SHIFT; + if (page->index >= end_index) { + /* + * The page straddles i_size. It must be zeroed out on each + * and every writepage invocation because it may be mmapped. + * "A file is mapped in multiples of the page size. For a file + * that is not a multiple of the page size, the remaining memory + * is zeroed when mapped, and writes to that region are not + * written out to the file." + */ + unsigned offset = i_size & (PAGE_SIZE - 1); + + if (page->index > end_index || !offset) + goto confused; + zero_user_segment(page, offset, PAGE_SIZE); + } + + /* + * This page will go to BIO. Do we need to send this BIO off first? + */ + if (bio && mpd->last_block_in_bio != blocks[0] - 1) + bio = mpage_bio_submit(bio); + +alloc_new: + if (bio == NULL) { + if (first_unmapped == blocks_per_page) { + if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9), + page, wbc)) + goto out; + } + bio = bio_alloc(bdev, BIO_MAX_VECS, + REQ_OP_WRITE | wbc_to_write_flags(wbc), + GFP_NOFS); + bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); + wbc_init_bio(wbc, bio); + } + + /* + * Must try to add the page before marking the buffer clean or + * the confused fail path above (OOM) will be very confused when + * it finds all bh marked clean (i.e. it will not write anything) + */ + wbc_account_cgroup_owner(wbc, page, PAGE_SIZE); + length = first_unmapped << blkbits; + if (bio_add_page(bio, page, length, 0) < length) { + bio = mpage_bio_submit(bio); + goto alloc_new; + } + + clean_buffers(page, first_unmapped); + + BUG_ON(PageWriteback(page)); + set_page_writeback(page); + unlock_page(page); + if (boundary || (first_unmapped != blocks_per_page)) { + bio = mpage_bio_submit(bio); + if (boundary_block) { + write_boundary_block(boundary_bdev, + boundary_block, 1 << blkbits); + } + } else { + mpd->last_block_in_bio = blocks[blocks_per_page - 1]; + } + goto out; + +confused: + if (bio) + bio = mpage_bio_submit(bio); + + /* + * The caller has a ref on the inode, so *mapping is stable + */ + ret = block_write_full_page(page, mpd->get_block, wbc); + mapping_set_error(mapping, ret); +out: + mpd->bio = bio; + return ret; +} + +/** + * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them + * @mapping: address space structure to write + * @wbc: subtract the number of written pages from *@wbc->nr_to_write + * @get_block: the filesystem's block mapper function. + * + * This is a library function, which implements the writepages() + * address_space_operation. + * + * If a page is already under I/O, generic_writepages() skips it, even + * if it's dirty. This is desirable behaviour for memory-cleaning writeback, + * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() + * and msync() need to guarantee that all the data which was dirty at the time + * the call was made get new I/O started against them. If wbc->sync_mode is + * WB_SYNC_ALL then we were called for data integrity and we must wait for + * existing IO to complete. + */ +int +mpage_writepages(struct address_space *mapping, + struct writeback_control *wbc, get_block_t get_block) +{ + struct mpage_data mpd = { + .get_block = get_block, + }; + struct blk_plug plug; + int ret; + + blk_start_plug(&plug); + ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); + if (mpd.bio) + mpage_bio_submit(mpd.bio); + blk_finish_plug(&plug); + return ret; +} +EXPORT_SYMBOL(mpage_writepages); -- cgit v1.2.3