Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 641 insertions, 0 deletions

diff --git a/mm/readahead.c b/mm/readahead.c
new file mode 100644
index 000000000..d30bcf4bc
--- /dev/null
+++ b/mm/readahead.c
@@ -0,0 +1,641 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * mm/readahead.c - address_space-level file readahead.
+ *
+ * Copyright (C) 2002, Linus Torvalds
+ *
+ * 09Apr2002	Andrew Morton
+ *		Initial version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/dax.h>
+#include <linux/gfp.h>
+#include <linux/export.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/pagevec.h>
+#include <linux/pagemap.h>
+#include <linux/syscalls.h>
+#include <linux/file.h>
+#include <linux/mm_inline.h>
+#include <linux/blk-cgroup.h>
+#include <linux/fadvise.h>
+#include <linux/sched/mm.h>
+
+#include "internal.h"
+
+/*
+ * Initialise a struct file's readahead state.  Assumes that the caller has
+ * memset *ra to zero.
+ */
+void
+file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
+{
+	ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
+	ra->prev_pos = -1;
+}
+EXPORT_SYMBOL_GPL(file_ra_state_init);
+
+/*
+ * see if a page needs releasing upon read_cache_pages() failure
+ * - the caller of read_cache_pages() may have set PG_private or PG_fscache
+ *   before calling, such as the NFS fs marking pages that are cached locally
+ *   on disk, thus we need to give the fs a chance to clean up in the event of
+ *   an error
+ */
+static void read_cache_pages_invalidate_page(struct address_space *mapping,
+					     struct page *page)
+{
+	if (page_has_private(page)) {
+		if (!trylock_page(page))
+			BUG();
+		page->mapping = mapping;
+		do_invalidatepage(page, 0, PAGE_SIZE);
+		page->mapping = NULL;
+		unlock_page(page);
+	}
+	put_page(page);
+}
+
+/*
+ * release a list of pages, invalidating them first if need be
+ */
+static void read_cache_pages_invalidate_pages(struct address_space *mapping,
+					      struct list_head *pages)
+{
+	struct page *victim;
+
+	while (!list_empty(pages)) {
+		victim = lru_to_page(pages);
+		list_del(&victim->lru);
+		read_cache_pages_invalidate_page(mapping, victim);
+	}
+}
+
+/**
+ * read_cache_pages - populate an address space with some pages & start reads against them
+ * @mapping: the address_space
+ * @pages: The address of a list_head which contains the target pages.  These
+ *   pages have their ->index populated and are otherwise uninitialised.
+ * @filler: callback routine for filling a single page.
+ * @data: private data for the callback routine.
+ *
+ * Hides the details of the LRU cache etc from the filesystems.
+ *
+ * Returns: %0 on success, error return by @filler otherwise
+ */
+int read_cache_pages(struct address_space *mapping, struct list_head *pages,
+			int (*filler)(void *, struct page *), void *data)
+{
+	struct page *page;
+	int ret = 0;
+
+	while (!list_empty(pages)) {
+		page = lru_to_page(pages);
+		list_del(&page->lru);
+		if (add_to_page_cache_lru(page, mapping, page->index,
+				readahead_gfp_mask(mapping))) {
+			read_cache_pages_invalidate_page(mapping, page);
+			continue;
+		}
+		put_page(page);
+
+		ret = filler(data, page);
+		if (unlikely(ret)) {
+			read_cache_pages_invalidate_pages(mapping, pages);
+			break;
+		}
+		task_io_account_read(PAGE_SIZE);
+	}
+	return ret;
+}
+
+EXPORT_SYMBOL(read_cache_pages);
+
+static void read_pages(struct readahead_control *rac, struct list_head *pages,
+		bool skip_page)
+{
+	const struct address_space_operations *aops = rac->mapping->a_ops;
+	struct page *page;
+	struct blk_plug plug;
+
+	if (!readahead_count(rac))
+		goto out;
+
+	blk_start_plug(&plug);
+
+	if (aops->readahead) {
+		aops->readahead(rac);
+		/* Clean up the remaining pages */
+		while ((page = readahead_page(rac))) {
+			unlock_page(page);
+			put_page(page);
+		}
+	} else if (aops->readpages) {
+		aops->readpages(rac->file, rac->mapping, pages,
+				readahead_count(rac));
+		/* Clean up the remaining pages */
+		put_pages_list(pages);
+		rac->_index += rac->_nr_pages;
+		rac->_nr_pages = 0;
+	} else {
+		while ((page = readahead_page(rac))) {
+			aops->readpage(rac->file, page);
+			put_page(page);
+		}
+	}
+
+	blk_finish_plug(&plug);
+
+	BUG_ON(!list_empty(pages));
+	BUG_ON(readahead_count(rac));
+
+out:
+	if (skip_page)
+		rac->_index++;
+}
+
+/**
+ * page_cache_ra_unbounded - Start unchecked readahead.
+ * @ractl: Readahead control.
+ * @nr_to_read: The number of pages to read.
+ * @lookahead_size: Where to start the next readahead.
+ *
+ * This function is for filesystems to call when they want to start
+ * readahead beyond a file's stated i_size.  This is almost certainly
+ * not the function you want to call.  Use page_cache_async_readahead()
+ * or page_cache_sync_readahead() instead.
+ *
+ * Context: File is referenced by caller.  Mutexes may be held by caller.
+ * May sleep, but will not reenter filesystem to reclaim memory.
+ */
+void page_cache_ra_unbounded(struct readahead_control *ractl,
+		unsigned long nr_to_read, unsigned long lookahead_size)
+{
+	struct address_space *mapping = ractl->mapping;
+	unsigned long index = readahead_index(ractl);
+	LIST_HEAD(page_pool);
+	gfp_t gfp_mask = readahead_gfp_mask(mapping);
+	unsigned long i;
+
+	/*
+	 * Partway through the readahead operation, we will have added
+	 * locked pages to the page cache, but will not yet have submitted
+	 * them for I/O.  Adding another page may need to allocate memory,
+	 * which can trigger memory reclaim.  Telling the VM we're in
+	 * the middle of a filesystem operation will cause it to not
+	 * touch file-backed pages, preventing a deadlock.  Most (all?)
+	 * filesystems already specify __GFP_NOFS in their mapping's
+	 * gfp_mask, but let's be explicit here.
+	 */
+	unsigned int nofs = memalloc_nofs_save();
+
+	/*
+	 * Preallocate as many pages as we will need.
+	 */
+	for (i = 0; i < nr_to_read; i++) {
+		struct page *page = xa_load(&mapping->i_pages, index + i);
+
+		BUG_ON(index + i != ractl->_index + ractl->_nr_pages);
+
+		if (page && !xa_is_value(page)) {
+			/*
+			 * Page already present?  Kick off the current batch
+			 * of contiguous pages before continuing with the
+			 * next batch.  This page may be the one we would
+			 * have intended to mark as Readahead, but we don't
+			 * have a stable reference to this page, and it's
+			 * not worth getting one just for that.
+			 */
+			read_pages(ractl, &page_pool, true);
+			continue;
+		}
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			break;
+		if (mapping->a_ops->readpages) {
+			page->index = index + i;
+			list_add(&page->lru, &page_pool);
+		} else if (add_to_page_cache_lru(page, mapping, index + i,
+					gfp_mask) < 0) {
+			put_page(page);
+			read_pages(ractl, &page_pool, true);
+			continue;
+		}
+		if (i == nr_to_read - lookahead_size)
+			SetPageReadahead(page);
+		ractl->_nr_pages++;
+	}
+
+	/*
+	 * Now start the IO.  We ignore I/O errors - if the page is not
+	 * uptodate then the caller will launch readpage again, and
+	 * will then handle the error.
+	 */
+	read_pages(ractl, &page_pool, false);
+	memalloc_nofs_restore(nofs);
+}
+EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
+
+/*
+ * do_page_cache_ra() actually reads a chunk of disk.  It allocates
+ * the pages first, then submits them for I/O. This avoids the very bad
+ * behaviour which would occur if page allocations are causing VM writeback.
+ * We really don't want to intermingle reads and writes like that.
+ */
+void do_page_cache_ra(struct readahead_control *ractl,
+		unsigned long nr_to_read, unsigned long lookahead_size)
+{
+	struct inode *inode = ractl->mapping->host;
+	unsigned long index = readahead_index(ractl);
+	loff_t isize = i_size_read(inode);
+	pgoff_t end_index;	/* The last page we want to read */
+
+	if (isize == 0)
+		return;
+
+	end_index = (isize - 1) >> PAGE_SHIFT;
+	if (index > end_index)
+		return;
+	/* Don't read past the page containing the last byte of the file */
+	if (nr_to_read > end_index - index)
+		nr_to_read = end_index - index + 1;
+
+	page_cache_ra_unbounded(ractl, nr_to_read, lookahead_size);
+}
+
+/*
+ * Chunk the readahead into 2 megabyte units, so that we don't pin too much
+ * memory at once.
+ */
+void force_page_cache_ra(struct readahead_control *ractl,
+		struct file_ra_state *ra, unsigned long nr_to_read)
+{
+	struct address_space *mapping = ractl->mapping;
+	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
+	unsigned long max_pages, index;
+
+	if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages &&
+			!mapping->a_ops->readahead))
+		return;
+
+	/*
+	 * If the request exceeds the readahead window, allow the read to
+	 * be up to the optimal hardware IO size
+	 */
+	index = readahead_index(ractl);
+	max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
+	nr_to_read = min_t(unsigned long, nr_to_read, max_pages);
+	while (nr_to_read) {
+		unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE;
+
+		if (this_chunk > nr_to_read)
+			this_chunk = nr_to_read;
+		ractl->_index = index;
+		do_page_cache_ra(ractl, this_chunk, 0);
+
+		index += this_chunk;
+		nr_to_read -= this_chunk;
+	}
+}
+
+/*
+ * Set the initial window size, round to next power of 2 and square
+ * for small size, x 4 for medium, and x 2 for large
+ * for 128k (32 page) max ra
+ * 1-8 page = 32k initial, > 8 page = 128k initial
+ */
+static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
+{
+	unsigned long newsize = roundup_pow_of_two(size);
+
+	if (newsize <= max / 32)
+		newsize = newsize * 4;
+	else if (newsize <= max / 4)
+		newsize = newsize * 2;
+	else
+		newsize = max;
+
+	return newsize;
+}
+
+/*
+ *  Get the previous window size, ramp it up, and
+ *  return it as the new window size.
+ */
+static unsigned long get_next_ra_size(struct file_ra_state *ra,
+				      unsigned long max)
+{
+	unsigned long cur = ra->size;
+
+	if (cur < max / 16)
+		return 4 * cur;
+	if (cur <= max / 2)
+		return 2 * cur;
+	return max;
+}
+
+/*
+ * On-demand readahead design.
+ *
+ * The fields in struct file_ra_state represent the most-recently-executed
+ * readahead attempt:
+ *
+ *                        |<----- async_size ---------|
+ *     |------------------- size -------------------->|
+ *     |==================#===========================|
+ *     ^start             ^page marked with PG_readahead
+ *
+ * To overlap application thinking time and disk I/O time, we do
+ * `readahead pipelining': Do not wait until the application consumed all
+ * readahead pages and stalled on the missing page at readahead_index;
+ * Instead, submit an asynchronous readahead I/O as soon as there are
+ * only async_size pages left in the readahead window. Normally async_size
+ * will be equal to size, for maximum pipelining.
+ *
+ * In interleaved sequential reads, concurrent streams on the same fd can
+ * be invalidating each other's readahead state. So we flag the new readahead
+ * page at (start+size-async_size) with PG_readahead, and use it as readahead
+ * indicator. The flag won't be set on already cached pages, to avoid the
+ * readahead-for-nothing fuss, saving pointless page cache lookups.
+ *
+ * prev_pos tracks the last visited byte in the _previous_ read request.
+ * It should be maintained by the caller, and will be used for detecting
+ * small random reads. Note that the readahead algorithm checks loosely
+ * for sequential patterns. Hence interleaved reads might be served as
+ * sequential ones.
+ *
+ * There is a special-case: if the first page which the application tries to
+ * read happens to be the first page of the file, it is assumed that a linear
+ * read is about to happen and the window is immediately set to the initial size
+ * based on I/O request size and the max_readahead.
+ *
+ * The code ramps up the readahead size aggressively at first, but slow down as
+ * it approaches max_readhead.
+ */
+
+/*
+ * Count contiguously cached pages from @index-1 to @index-@max,
+ * this count is a conservative estimation of
+ * 	- length of the sequential read sequence, or
+ * 	- thrashing threshold in memory tight systems
+ */
+static pgoff_t count_history_pages(struct address_space *mapping,
+				   pgoff_t index, unsigned long max)
+{
+	pgoff_t head;
+
+	rcu_read_lock();
+	head = page_cache_prev_miss(mapping, index - 1, max);
+	rcu_read_unlock();
+
+	return index - 1 - head;
+}
+
+/*
+ * page cache context based read-ahead
+ */
+static int try_context_readahead(struct address_space *mapping,
+				 struct file_ra_state *ra,
+				 pgoff_t index,
+				 unsigned long req_size,
+				 unsigned long max)
+{
+	pgoff_t size;
+
+	size = count_history_pages(mapping, index, max);
+
+	/*
+	 * not enough history pages:
+	 * it could be a random read
+	 */
+	if (size <= req_size)
+		return 0;
+
+	/*
+	 * starts from beginning of file:
+	 * it is a strong indication of long-run stream (or whole-file-read)
+	 */
+	if (size >= index)
+		size *= 2;
+
+	ra->start = index;
+	ra->size = min(size + req_size, max);
+	ra->async_size = 1;
+
+	return 1;
+}
+
+/*
+ * A minimal readahead algorithm for trivial sequential/random reads.
+ */
+static void ondemand_readahead(struct readahead_control *ractl,
+		struct file_ra_state *ra, bool hit_readahead_marker,
+		unsigned long req_size)
+{
+	struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
+	unsigned long max_pages = ra->ra_pages;
+	unsigned long add_pages;
+	unsigned long index = readahead_index(ractl);
+	pgoff_t prev_index;
+
+	/*
+	 * If the request exceeds the readahead window, allow the read to
+	 * be up to the optimal hardware IO size
+	 */
+	if (req_size > max_pages && bdi->io_pages > max_pages)
+		max_pages = min(req_size, bdi->io_pages);
+
+	/*
+	 * start of file
+	 */
+	if (!index)
+		goto initial_readahead;
+
+	/*
+	 * It's the expected callback index, assume sequential access.
+	 * Ramp up sizes, and push forward the readahead window.
+	 */
+	if ((index == (ra->start + ra->size - ra->async_size) ||
+	     index == (ra->start + ra->size))) {
+		ra->start += ra->size;
+		ra->size = get_next_ra_size(ra, max_pages);
+		ra->async_size = ra->size;
+		goto readit;
+	}
+
+	/*
+	 * Hit a marked page without valid readahead state.
+	 * E.g. interleaved reads.
+	 * Query the pagecache for async_size, which normally equals to
+	 * readahead size. Ramp it up and use it as the new readahead size.
+	 */
+	if (hit_readahead_marker) {
+		pgoff_t start;
+
+		rcu_read_lock();
+		start = page_cache_next_miss(ractl->mapping, index + 1,
+				max_pages);
+		rcu_read_unlock();
+
+		if (!start || start - index > max_pages)
+			return;
+
+		ra->start = start;
+		ra->size = start - index;	/* old async_size */
+		ra->size += req_size;
+		ra->size = get_next_ra_size(ra, max_pages);
+		ra->async_size = ra->size;
+		goto readit;
+	}
+
+	/*
+	 * oversize read
+	 */
+	if (req_size > max_pages)
+		goto initial_readahead;
+
+	/*
+	 * sequential cache miss
+	 * trivial case: (index - prev_index) == 1
+	 * unaligned reads: (index - prev_index) == 0
+	 */
+	prev_index = (unsigned long long)ra->prev_pos >> PAGE_SHIFT;
+	if (index - prev_index <= 1UL)
+		goto initial_readahead;
+
+	/*
+	 * Query the page cache and look for the traces(cached history pages)
+	 * that a sequential stream would leave behind.
+	 */
+	if (try_context_readahead(ractl->mapping, ra, index, req_size,
+			max_pages))
+		goto readit;
+
+	/*
+	 * standalone, small random read
+	 * Read as is, and do not pollute the readahead state.
+	 */
+	do_page_cache_ra(ractl, req_size, 0);
+	return;
+
+initial_readahead:
+	ra->start = index;
+	ra->size = get_init_ra_size(req_size, max_pages);
+	ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;
+
+readit:
+	/*
+	 * Will this read hit the readahead marker made by itself?
+	 * If so, trigger the readahead marker hit now, and merge
+	 * the resulted next readahead window into the current one.
+	 * Take care of maximum IO pages as above.
+	 */
+	if (index == ra->start && ra->size == ra->async_size) {
+		add_pages = get_next_ra_size(ra, max_pages);
+		if (ra->size + add_pages <= max_pages) {
+			ra->async_size = add_pages;
+			ra->size += add_pages;
+		} else {
+			ra->size = max_pages;
+			ra->async_size = max_pages >> 1;
+		}
+	}
+
+	ractl->_index = ra->start;
+	do_page_cache_ra(ractl, ra->size, ra->async_size);
+}
+
+void page_cache_sync_ra(struct readahead_control *ractl,
+		struct file_ra_state *ra, unsigned long req_count)
+{
+	bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
+
+	/*
+	 * Even if read-ahead is disabled, issue this request as read-ahead
+	 * as we'll need it to satisfy the requested range. The forced
+	 * read-ahead will do the right thing and limit the read to just the
+	 * requested range, which we'll set to 1 page for this case.
+	 */
+	if (!ra->ra_pages || blk_cgroup_congested()) {
+		if (!ractl->file)
+			return;
+		req_count = 1;
+		do_forced_ra = true;
+	}
+
+	/* be dumb */
+	if (do_forced_ra) {
+		force_page_cache_ra(ractl, ra, req_count);
+		return;
+	}
+
+	/* do read-ahead */
+	ondemand_readahead(ractl, ra, false, req_count);
+}
+EXPORT_SYMBOL_GPL(page_cache_sync_ra);
+
+void page_cache_async_ra(struct readahead_control *ractl,
+		struct file_ra_state *ra, struct page *page,
+		unsigned long req_count)
+{
+	/* no read-ahead */
+	if (!ra->ra_pages)
+		return;
+
+	/*
+	 * Same bit is used for PG_readahead and PG_reclaim.
+	 */
+	if (PageWriteback(page))
+		return;
+
+	ClearPageReadahead(page);
+
+	/*
+	 * Defer asynchronous read-ahead on IO congestion.
+	 */
+	if (inode_read_congested(ractl->mapping->host))
+		return;
+
+	if (blk_cgroup_congested())
+		return;
+
+	/* do read-ahead */
+	ondemand_readahead(ractl, ra, true, req_count);
+}
+EXPORT_SYMBOL_GPL(page_cache_async_ra);
+
+ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
+{
+	ssize_t ret;
+	struct fd f;
+
+	ret = -EBADF;
+	f = fdget(fd);
+	if (!f.file || !(f.file->f_mode & FMODE_READ))
+		goto out;
+
+	/*
+	 * The readahead() syscall is intended to run only on files
+	 * that can execute readahead. If readahead is not possible
+	 * on this file, then we must return -EINVAL.
+	 */
+	ret = -EINVAL;
+	if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
+	    (!S_ISREG(file_inode(f.file)->i_mode) &&
+	    !S_ISBLK(file_inode(f.file)->i_mode)))
+		goto out;
+
+	ret = vfs_fadvise(f.file, offset, count, POSIX_FADV_WILLNEED);
+out:
+	fdput(f);
+	return ret;
+}
+
+SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
+{
+	return ksys_readahead(fd, offset, count);
+}