cregit-Linux how code gets into the kernel

Release 4.8 mm/readahead.c

Directory: mm
 * 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 "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; }


andrew mortonandrew morton2468.57%125.00%
miquel van smoorenburgmiquel van smoorenburg617.14%125.00%
christoph hellwigchristoph hellwig411.43%125.00%
wu fengguangwu fengguang12.86%125.00%

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); }


david howellsdavid howells6495.52%250.00%
kirill a. shutemovkirill a. shutemov22.99%125.00%
lukas czernerlukas czerner11.49%125.00%

/* * 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); } }


david howellsdavid howells5298.11%150.00%
geliang tanggeliang tang11.89%150.00%

/** * 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. */
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; }


wu fengguangwu fengguang5943.70%215.38%
andrew mortonandrew morton5137.78%430.77%
david howellsdavid howells118.15%215.38%
nick pigginnick piggin75.19%17.69%
michal hockomichal hocko42.96%215.38%
kirill a. shutemovkirill a. shutemov21.48%17.69%
geliang tanggeliang tang10.74%17.69%

static int read_pages(struct address_space *mapping, struct file *filp, struct list_head *pages, unsigned int nr_pages, gfp_t gfp) { struct blk_plug plug; unsigned page_idx; int ret; blk_start_plug(&plug); if (mapping->a_ops->readpages) { ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages); /* Clean up the remaining pages */ put_pages_list(pages); goto out; } for (page_idx = 0; page_idx < nr_pages; page_idx++) { struct page *page = lru_to_page(pages); list_del(&page->lru); if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) mapping->a_ops->readpage(filp, page); put_page(page); } ret = 0; out: blk_finish_plug(&plug); return ret; }


wu fengguangwu fengguang8553.12%218.18%
andrew mortonandrew morton3823.75%327.27%
jens axboejens axboe1610.00%19.09%
steven prattsteven pratt138.12%19.09%
michal hockomichal hocko53.12%19.09%
geliang tanggeliang tang10.62%19.09%
kirill a. shutemovkirill a. shutemov10.62%19.09%
nick pigginnick piggin10.62%19.09%

/* * __do_page_cache_readahead() actually reads a chunk of disk. It allocates all * the pages first, then submits them all 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. * * Returns the number of pages requested, or the maximum amount of I/O allowed. */
int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, pgoff_t offset, unsigned long nr_to_read, unsigned long lookahead_size) { struct inode *inode = mapping->host; struct page *page; unsigned long end_index; /* The last page we want to read */ LIST_HEAD(page_pool); int page_idx; int ret = 0; loff_t isize = i_size_read(inode); gfp_t gfp_mask = readahead_gfp_mask(mapping); if (isize == 0) goto out; end_index = ((isize - 1) >> PAGE_SHIFT); /* * Preallocate as many pages as we will need. */ for (page_idx = 0; page_idx < nr_to_read; page_idx++) { pgoff_t page_offset = offset + page_idx; if (page_offset > end_index) break; rcu_read_lock(); page = radix_tree_lookup(&mapping->page_tree, page_offset); rcu_read_unlock(); if (page && !radix_tree_exceptional_entry(page)) continue; page = __page_cache_alloc(gfp_mask); if (!page) break; page->index = page_offset; list_add(&page->lru, &page_pool); if (page_idx == nr_to_read - lookahead_size) SetPageReadahead(page); ret++; } /* * 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. */ if (ret) read_pages(mapping, filp, &page_pool, ret, gfp_mask); BUG_ON(!list_empty(&page_pool)); out: return ret; }


wu fengguangwu fengguang14762.82%18.33%
oleg nesterovoleg nesterov2410.26%325.00%
andrew mortonandrew morton198.12%216.67%
ram pairam pai187.69%18.33%
michal hockomichal hocko125.13%18.33%
johannes weinerjohannes weiner62.56%18.33%
nick pigginnick piggin62.56%18.33%
fabian frederickfabian frederick10.43%18.33%
kirill a. shutemovkirill a. shutemov10.43%18.33%

/* * Chunk the readahead into 2 megabyte units, so that we don't pin too much * memory at once. */
int force_page_cache_readahead(struct address_space *mapping, struct file *filp, pgoff_t offset, unsigned long nr_to_read) { if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) return -EINVAL; nr_to_read = min(nr_to_read, inode_to_bdi(mapping->host)->ra_pages); while (nr_to_read) { int err; unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE; if (this_chunk > nr_to_read) this_chunk = nr_to_read; err = __do_page_cache_readahead(mapping, filp, offset, this_chunk, 0); if (err < 0) return err; offset += this_chunk; nr_to_read -= this_chunk; } return 0; }


wu fengguangwu fengguang5441.86%16.25%
andrew mortonandrew morton2116.28%531.25%
steven prattsteven pratt2015.50%16.25%
roman gushchinroman gushchin107.75%16.25%
david howellsdavid howells75.43%16.25%
fengguang wufengguang wu64.65%16.25%
ram pairam pai43.10%212.50%
mark rutlandmark rutland32.33%16.25%
oleg nesterovoleg nesterov32.33%212.50%
kirill a. shutemovkirill a. shutemov10.78%16.25%

/* * 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; }


wu fengguangwu fengguang61100.00%1100.00%

/* * 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; unsigned long newsize; if (cur < max / 16) newsize = 4 * cur; else newsize = 2 * cur; return min(newsize, max); }


wu fengguangwu fengguang57100.00%3100.00%

/* * 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 @offset-1 to @offset-@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 offset, unsigned long max) { pgoff_t head; rcu_read_lock(); head = page_cache_prev_hole(mapping, offset - 1, max); rcu_read_unlock(); return offset - 1 - head; }


fengguang wufengguang wu4697.87%150.00%
johannes weinerjohannes weiner12.13%150.00%

/* * page cache context based read-ahead */
static int try_context_readahead(struct address_space *mapping, struct file_ra_state *ra, pgoff_t offset, unsigned long req_size, unsigned long max) { pgoff_t size; size = count_history_pages(mapping, offset, 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 >= offset) size *= 2; ra->start = offset; ra->size = min(size + req_size, max); ra->async_size = 1; return 1; }


fengguang wufengguang wu90100.00%2100.00%

/* * A minimal readahead algorithm for trivial sequential/random reads. */
static unsigned long ondemand_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, bool hit_readahead_marker, pgoff_t offset, unsigned long req_size) { unsigned long max = ra->ra_pages; pgoff_t prev_offset; /* * start of file */ if (!offset) goto initial_readahead; /* * It's the expected callback offset, assume sequential access. * Ramp up sizes, and push forward the readahead window. */ if ((offset == (ra->start + ra->size - ra->async_size) || offset == (ra->start + ra->size))) { ra->start += ra->size; ra->size = get_next_ra_size(ra, max); 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_hole(mapping, offset + 1, max); rcu_read_unlock(); if (!start || start - offset > max) return 0; ra->start = start; ra->size = start - offset; /* old async_size */ ra->size += req_size; ra->size = get_next_ra_size(ra, max); ra->async_size = ra->size; goto readit; } /* * oversize read */ if (req_size > max) goto initial_readahead; /* * sequential cache miss * trivial case: (offset - prev_offset) == 1 * unaligned reads: (offset - prev_offset) == 0 */ prev_offset = (unsigned long long)ra->prev_pos >> PAGE_SHIFT; if (offset - prev_offset <= 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(mapping, ra, offset, req_size, max)) goto readit; /* * standalone, small random read * Read as is, and do not pollute the readahead state. */ return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); initial_readahead: ra->start = offset; ra->size = get_init_ra_size(req_size, max); 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. */ if (offset == ra->start && ra->size == ra->async_size) { ra->async_size = get_next_ra_size(ra, max); ra->size += ra->async_size; } return ra_submit(ra, mapping, filp); }


wu fengguangwu fengguang22361.77%531.25%
fengguang wufengguang wu11431.58%637.50%
damien ramondadamien ramonda164.43%16.25%
nick pigginnick piggin41.11%16.25%
rusty russellrusty russell20.55%16.25%
kirill a. shutemovkirill a. shutemov10.28%16.25%
johannes weinerjohannes weiner10.28%16.25%

/** * page_cache_sync_readahead - generic file readahead * @mapping: address_space which holds the pagecache and I/O vectors * @ra: file_ra_state which holds the readahead state * @filp: passed on to ->readpage() and ->readpages() * @offset: start offset into @mapping, in pagecache page-sized units * @req_size: hint: total size of the read which the caller is performing in * pagecache pages * * page_cache_sync_readahead() should be called when a cache miss happened: * it will submit the read. The readahead logic may decide to piggyback more * pages onto the read request if access patterns suggest it will improve * performance. */
void page_cache_sync_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, pgoff_t offset, unsigned long req_size) { /* no read-ahead */ if (!ra->ra_pages) return; /* be dumb */ if (filp && (filp->f_mode & FMODE_RANDOM)) { force_page_cache_readahead(mapping, filp, offset, req_size); return; } /* do read-ahead */ ondemand_readahead(mapping, ra, filp, false, offset, req_size); }


rusty russellrusty russell5063.29%125.00%
fengguang wufengguang wu2734.18%250.00%
wu fengguangwu fengguang22.53%125.00%

EXPORT_SYMBOL_GPL(page_cache_sync_readahead); /** * page_cache_async_readahead - file readahead for marked pages * @mapping: address_space which holds the pagecache and I/O vectors * @ra: file_ra_state which holds the readahead state * @filp: passed on to ->readpage() and ->readpages() * @page: the page at @offset which has the PG_readahead flag set * @offset: start offset into @mapping, in pagecache page-sized units * @req_size: hint: total size of the read which the caller is performing in * pagecache pages * * page_cache_async_readahead() should be called when a page is used which * has the PG_readahead flag; this is a marker to suggest that the application * has used up enough of the readahead window that we should start pulling in * more pages. */
void page_cache_async_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, struct page *page, pgoff_t offset, unsigned long req_size) { /* 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(mapping->host)) return; /* do read-ahead */ ondemand_readahead(mapping, ra, filp, true, offset, req_size); }


wu fengguangwu fengguang6984.15%240.00%
rusty russellrusty russell910.98%120.00%
christoph hellwigchristoph hellwig33.66%120.00%
tejun heotejun heo11.22%120.00%

static ssize_t do_readahead(struct address_space *mapping, struct file *filp, pgoff_t index, unsigned long nr) { if (!mapping || !mapping->a_ops) return -EINVAL; /* * Readahead doesn't make sense for DAX inodes, but we don't want it * to report a failure either. Instead, we just return success and * don't do any work. */ if (dax_mapping(mapping)) return 0; return force_page_cache_readahead(mapping, filp, index, nr); }


americo wangamerico wang4880.00%133.33%
ross zwislerross zwisler1118.33%133.33%
mark rutlandmark rutland11.67%133.33%

SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) { ssize_t ret; struct fd f; ret = -EBADF; f = fdget(fd); if (f.file) { if (f.file->f_mode & FMODE_READ) { struct address_space *mapping = f.file->f_mapping; pgoff_t start = offset >> PAGE_SHIFT; pgoff_t end = (offset + count - 1) >> PAGE_SHIFT; unsigned long len = end - start + 1; ret = do_readahead(mapping, f.file, start, len); } fdput(f); } return ret; }

Overall Contributors

wu fengguangwu fengguang77341.90%79.33%
fengguang wufengguang wu28615.50%1114.67%
andrew mortonandrew morton1699.16%1621.33%
americo wangamerico wang1427.70%11.33%
david howellsdavid howells1367.37%34.00%
rusty russellrusty russell683.69%11.33%
steven prattsteven pratt331.79%11.33%
al viroal viro311.68%34.00%
oleg nesterovoleg nesterov271.46%34.00%
ram pairam pai221.19%22.67%
michal hockomichal hocko211.14%22.67%
jens axboejens axboe191.03%22.67%
nick pigginnick piggin180.98%34.00%
damien ramondadamien ramonda160.87%11.33%
ross zwislerross zwisler140.76%11.33%
kirill a. shutemovkirill a. shutemov100.54%11.33%
roman gushchinroman gushchin100.54%11.33%
johannes weinerjohannes weiner80.43%22.67%
christoph hellwigchristoph hellwig70.38%11.33%
miquel van smoorenburgmiquel van smoorenburg60.33%11.33%
geliang tanggeliang tang60.33%22.67%
steven whitehousesteven whitehouse50.27%11.33%
mark rutlandmark rutland40.22%11.33%
tejun heotejun heo40.22%22.67%
fabian frederickfabian frederick40.22%11.33%
arnaldo carvalho de meloarnaldo carvalho de melo20.11%11.33%
lukas czernerlukas czerner10.05%11.33%
paul gortmakerpaul gortmaker10.05%11.33%
huang shijiehuang shijie10.05%11.33%
francois camifrancois cami10.05%11.33%
Directory: mm
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.