Orange Pi5 kernel

// 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 <trace/hooks/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);
 
gfp_t readahead_gfp_mask(struct address_space *x)
{
<------>gfp_t mask = mapping_gfp_mask(x) | __GFP_NORETRY | __GFP_NOWARN;
 
<------>trace_android_rvh_set_readahead_gfp_mask(&mask);
<------>return mask;
}
EXPORT_SYMBOL_GPL(readahead_gfp_mask);
 
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);
 
<------>trace_android_vh_ra_tuning_max_page(ractl, &max_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))
<------><------>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);
}