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page cache: Convert find_get_entry to XArray

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Slightly shorter and simpler code.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-05-16 16:12:50 -04:00
parent 5c024e6a4e
commit 4c7472c0df
1 changed files with 28 additions and 35 deletions
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63
mm/filemap.c
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@ -1382,47 +1382,40 @@ EXPORT_SYMBOL(page_cache_prev_miss);
*/
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
{
void **pagep;
XA_STATE(xas, &mapping->i_pages, offset);
struct page *head, *page;
rcu_read_lock();
repeat:
page = NULL;
pagep = radix_tree_lookup_slot(&mapping->i_pages, offset);
if (pagep) {
page = radix_tree_deref_slot(pagep);
if (unlikely(!page))
goto out;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page))
goto repeat;
/*
* A shadow entry of a recently evicted page,
* or a swap entry from shmem/tmpfs. Return
* it without attempting to raise page count.
*/
goto out;
}
xas_reset(&xas);
page = xas_load(&xas);
if (xas_retry(&xas, page))
goto repeat;
/*
* A shadow entry of a recently evicted page, or a swap entry from
* shmem/tmpfs. Return it without attempting to raise page count.
*/
if (!page || xa_is_value(page))
goto out;
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/*
* Has the page moved?
* This is part of the lockless pagecache protocol. See
* include/linux/pagemap.h for details.
*/
if (unlikely(page != *pagep)) {
put_page(head);
goto repeat;
}
/*
* Has the page moved?
* This is part of the lockless pagecache protocol. See
* include/linux/pagemap.h for details.
*/
if (unlikely(page != xas_reload(&xas))) {
put_page(head);
goto repeat;
}
out:
rcu_read_unlock();
@ -1453,7 +1446,7 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
repeat:
page = find_get_entry(mapping, offset);
if (page && !radix_tree_exception(page)) {
if (page && !xa_is_value(page)) {
lock_page(page);
/* Has the page been truncated? */
if (unlikely(page_mapping(page) != mapping)) {