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mm: add find_get_entries_tag()

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Add find_get_entries_tag() to the family of functions that include
find_get_entries(), find_get_pages() and find_get_pages_tag().  This is
needed for DAX dirty page handling because we need a list of both page
offsets and radix tree entries ('indices' and 'entries' in this
function) that are marked with the PAGECACHE_TAG_TOWRITE tag.

Signed-off-by: Ross Zwisler <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jeff Layton <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Dave Hansen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Ross Zwisler 2016-01-22 15:10:44 -08:00 • committed by Linus Torvalds
commit 7e7f774984
2 changed files with 71 additions and 0 deletions
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68
mm/filemap.c
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@ -1499,6 +1499,74 @@ repeat:
}
EXPORT_SYMBOL(find_get_pages_tag);
/**
* find_get_entries_tag - find and return entries that match @tag
* @mapping: the address_space to search
* @start: the starting page cache index
* @tag: the tag index
* @nr_entries: the maximum number of entries
* @entries: where the resulting entries are placed
* @indices: the cache indices corresponding to the entries in @entries
*
* Like find_get_entries, except we only return entries which are tagged with
* @tag.
*/
unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
int tag, unsigned int nr_entries,
struct page **entries, pgoff_t *indices)
{
void **slot;
unsigned int ret = 0;
struct radix_tree_iter iter;
if (!nr_entries)
return 0;
rcu_read_lock();
restart:
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, start, tag) {
struct page *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
/*
* Transient condition which can only trigger
* when entry at index 0 moves out of or back
* to root: none yet gotten, safe to restart.
*/
goto restart;
}
/*
* A shadow entry of a recently evicted page, a swap
* entry from shmem/tmpfs or a DAX entry. Return it
* without attempting to raise page count.
*/
goto export;
}
if (!page_cache_get_speculative(page))
goto repeat;
/* Has the page moved? */
if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
export:
indices[ret] = iter.index;
entries[ret] = page;
if (++ret == nr_entries)
break;
}
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(find_get_entries_tag);
/*
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
* a _large_ part of the i/o request. Imagine the worst scenario: