*
* Copyright (C) 2002, Linus Torvalds
*
- * 09Apr2002 akpm@zip.com.au
+ * 09Apr2002 Andrew Morton
* Initial version.
*/
#include <linux/backing-dev.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/pagevec.h>
-
-void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
-{
-}
-EXPORT_SYMBOL(default_unplug_io_fn);
-
-/*
- * Convienent macros for min/max read-ahead pages.
- * Note that MAX_RA_PAGES is rounded down, while MIN_RA_PAGES is rounded up.
- * The latter is necessary for systems with large page size(i.e. 64k).
- */
-#define MAX_RA_PAGES (VM_MAX_READAHEAD*1024 / PAGE_CACHE_SIZE)
-#define MIN_RA_PAGES DIV_ROUND_UP(VM_MIN_READAHEAD*1024, PAGE_CACHE_SIZE)
-
-struct backing_dev_info default_backing_dev_info = {
- .ra_pages = MAX_RA_PAGES,
- .state = 0,
- .capabilities = BDI_CAP_MAP_COPY,
- .unplug_io_fn = default_unplug_io_fn,
-};
-EXPORT_SYMBOL_GPL(default_backing_dev_info);
+#include <linux/pagemap.h>
/*
* Initialise a struct file's readahead state. Assumes that the caller has
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
{
ra->ra_pages = mapping->backing_dev_info->ra_pages;
- ra->prev_index = -1;
+ ra->prev_pos = -1;
}
EXPORT_SYMBOL_GPL(file_ra_state_init);
int (*filler)(void *, struct page *), void *data)
{
struct page *page;
- struct pagevec lru_pvec;
int ret = 0;
- pagevec_init(&lru_pvec, 0);
-
while (!list_empty(pages)) {
page = list_to_page(pages);
list_del(&page->lru);
- if (add_to_page_cache(page, mapping, page->index, GFP_KERNEL)) {
+ if (add_to_page_cache_lru(page, mapping,
+ page->index, GFP_KERNEL)) {
page_cache_release(page);
continue;
}
+ page_cache_release(page);
+
ret = filler(data, page);
- if (!pagevec_add(&lru_pvec, page))
- __pagevec_lru_add(&lru_pvec);
- if (ret) {
+ if (unlikely(ret)) {
put_pages_list(pages);
break;
}
task_io_account_read(PAGE_CACHE_SIZE);
}
- pagevec_lru_add(&lru_pvec);
return ret;
}
struct list_head *pages, unsigned nr_pages)
{
unsigned page_idx;
- struct pagevec lru_pvec;
int ret;
if (mapping->a_ops->readpages) {
goto out;
}
- pagevec_init(&lru_pvec, 0);
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
struct page *page = list_to_page(pages);
list_del(&page->lru);
- if (!add_to_page_cache(page, mapping,
+ if (!add_to_page_cache_lru(page, mapping,
page->index, GFP_KERNEL)) {
mapping->a_ops->readpage(filp, page);
- if (!pagevec_add(&lru_pvec, page))
- __pagevec_lru_add(&lru_pvec);
- } else
- page_cache_release(page);
+ }
+ page_cache_release(page);
}
- pagevec_lru_add(&lru_pvec);
ret = 0;
out:
return ret;
/*
* Preallocate as many pages as we will need.
*/
- read_lock_irq(&mapping->tree_lock);
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)
continue;
- read_unlock_irq(&mapping->tree_lock);
page = page_cache_alloc_cold(mapping);
- read_lock_irq(&mapping->tree_lock);
if (!page)
break;
page->index = page_offset;
SetPageReadahead(page);
ret++;
}
- read_unlock_irq(&mapping->tree_lock);
/*
* Now start the IO. We ignore I/O errors - if the page is not
*/
unsigned long max_sane_readahead(unsigned long nr)
{
- return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE)
+ return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE_FILE)
+ node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2);
}
/*
* Submit IO for the read-ahead request in file_ra_state.
*/
-unsigned long ra_submit(struct file_ra_state *ra,
+static unsigned long ra_submit(struct file_ra_state *ra,
struct address_space *mapping, struct file *filp)
{
- unsigned long ra_size;
- unsigned long la_size;
int actual;
- ra_size = ra_readahead_size(ra);
- la_size = ra_lookahead_size(ra);
actual = __do_page_cache_readahead(mapping, filp,
- ra->ra_index, ra_size, la_size);
+ ra->start, ra->size, ra->async_size);
return actual;
}
-EXPORT_SYMBOL_GPL(ra_submit);
/*
* Set the initial window size, round to next power of 2 and square
static unsigned long get_next_ra_size(struct file_ra_state *ra,
unsigned long max)
{
- unsigned long cur = ra->readahead_index - ra->ra_index;
+ unsigned long cur = ra->size;
unsigned long newsize;
if (cur < max / 16)
* The fields in struct file_ra_state represent the most-recently-executed
* readahead attempt:
*
- * |-------- last readahead window -------->|
- * |-- application walking here -->|
- * ======#============|==================#=====================|
- * ^la_index ^ra_index ^lookahead_index ^readahead_index
- *
- * [ra_index, readahead_index) represents the last readahead window.
- *
- * [la_index, lookahead_index] is where the application would be walking(in
- * the common case of cache-cold sequential reads): the last window was
- * established when the application was at la_index, and the next window will
- * be bring in when the application reaches lookahead_index.
+ * |<----- 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 early as the application
- * reads on the page at lookahead_index. Normally lookahead_index will be
- * equal to ra_index, for maximum pipelining.
+ * 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 lookahead_index with PG_readahead, and use it as 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_index tracks the last visited page in the _previous_ read request.
+ * 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
bool hit_readahead_marker, pgoff_t offset,
unsigned long req_size)
{
- unsigned long max; /* max readahead pages */
- pgoff_t ra_index; /* readahead index */
- unsigned long ra_size; /* readahead size */
- unsigned long la_size; /* lookahead size */
- int sequential;
-
- max = ra->ra_pages;
- sequential = (offset - ra->prev_index <= 1UL) || (req_size > max);
+ int max = ra->ra_pages; /* max readahead pages */
+ pgoff_t prev_offset;
+ int sequential;
/*
- * Lookahead/readahead hit, assume sequential access.
+ * It's the expected callback offset, assume sequential access.
* Ramp up sizes, and push forward the readahead window.
*/
- if (offset && (offset == ra->lookahead_index ||
- offset == ra->readahead_index)) {
- ra_index = ra->readahead_index;
- ra_size = get_next_ra_size(ra, max);
- la_size = ra_size;
- goto fill_ra;
+ if (offset && (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;
}
+ prev_offset = ra->prev_pos >> PAGE_CACHE_SHIFT;
+ sequential = offset - prev_offset <= 1UL || req_size > max;
+
/*
* Standalone, small read.
* Read as is, and do not pollute the readahead state.
}
/*
+ * 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 = radix_tree_next_hole(&mapping->page_tree, offset,max+1);
+ rcu_read_unlock();
+
+ if (!start || start - offset > max)
+ return 0;
+
+ ra->start = start;
+ ra->size = start - offset; /* old async_size */
+ ra->size = get_next_ra_size(ra, max);
+ ra->async_size = ra->size;
+ goto readit;
+ }
+
+ /*
* It may be one of
* - first read on start of file
* - sequential cache miss
* - oversize random read
* Start readahead for it.
*/
- ra_index = offset;
- ra_size = get_init_ra_size(req_size, max);
- la_size = ra_size > req_size ? ra_size - req_size : ra_size;
-
- /*
- * Hit on a lookahead page without valid readahead state.
- * E.g. interleaved reads.
- * Not knowing its readahead pos/size, bet on the minimal possible one.
- */
- if (hit_readahead_marker) {
- ra_index++;
- ra_size = min(4 * ra_size, max);
- }
-
-fill_ra:
- ra_set_index(ra, offset, ra_index);
- ra_set_size(ra, ra_size, la_size);
+ 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:
return ra_submit(ra, mapping, filp);
}
* pagecache pages
*
* page_cache_async_ondemand() should be called when a page is used which
- * has the PG_readahead flag: this is a marker to suggest that the application
+ * 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. */
+ * more pages.
+ */
void
page_cache_async_readahead(struct address_space *mapping,
struct file_ra_state *ra, struct file *filp,
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff