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Message-Id: <20180219194556.6575-27-willy@infradead.org>
Date: Mon, 19 Feb 2018 11:45:21 -0800
From: Matthew Wilcox <willy@...radead.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <mawilcox@...rosoft.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org
Subject: [PATCH v7 26/61] page cache: Add page_cache_range_empty function
From: Matthew Wilcox <mawilcox@...rosoft.com>
btrfs has its own custom function for determining whether the page cache
has any pages in a particular range. Move this functionality to the
page cache, and call it from btrfs.
Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
fs/btrfs/btrfs_inode.h | 7 ++++-
fs/btrfs/inode.c | 70 -------------------------------------------------
include/linux/pagemap.h | 2 ++
mm/filemap.c | 26 ++++++++++++++++++
4 files changed, 34 insertions(+), 71 deletions(-)
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 63f0ccc92a71..a48bd6e0a0bb 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -365,6 +365,11 @@ static inline void btrfs_print_data_csum_error(struct btrfs_inode *inode,
logical_start, csum, csum_expected, mirror_num);
}
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end);
+static inline bool btrfs_page_exists_in_range(struct inode *inode,
+ loff_t start, loff_t end)
+{
+ return page_cache_range_empty(inode->i_mapping, start >> PAGE_SHIFT,
+ end >> PAGE_SHIFT);
+}
#endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fbb4291fcc57..89ce4d90e7f6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7425,76 +7425,6 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
return ret;
}
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end)
-{
- struct radix_tree_root *root = &inode->i_mapping->pages;
- bool found = false;
- void **pagep = NULL;
- struct page *page = NULL;
- unsigned long start_idx;
- unsigned long end_idx;
-
- start_idx = start >> PAGE_SHIFT;
-
- /*
- * end is the last byte in the last page. end == start is legal
- */
- end_idx = end >> PAGE_SHIFT;
-
- rcu_read_lock();
-
- /* Most of the code in this while loop is lifted from
- * find_get_page. It's been modified to begin searching from a
- * page and return just the first page found in that range. If the
- * found idx is less than or equal to the end idx then we know that
- * a page exists. If no pages are found or if those pages are
- * outside of the range then we're fine (yay!) */
- while (page == NULL &&
- radix_tree_gang_lookup_slot(root, &pagep, NULL, start_idx, 1)) {
- page = radix_tree_deref_slot(pagep);
- if (unlikely(!page))
- break;
-
- if (radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page)) {
- page = NULL;
- continue;
- }
- /*
- * Otherwise, shmem/tmpfs must be storing a swap entry
- * here so return it without attempting to raise page
- * count.
- */
- page = NULL;
- break; /* TODO: Is this relevant for this use case? */
- }
-
- if (!page_cache_get_speculative(page)) {
- page = NULL;
- continue;
- }
-
- /*
- * 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(page);
- page = NULL;
- }
- }
-
- if (page) {
- if (page->index <= end_idx)
- found = true;
- put_page(page);
- }
-
- rcu_read_unlock();
- return found;
-}
-
static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
struct extent_state **cached_state, int writing)
{
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 0db127c3ccac..34d4fa3ad1c5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -245,6 +245,8 @@ pgoff_t page_cache_next_gap(struct address_space *mapping,
pgoff_t index, unsigned long max_scan);
pgoff_t page_cache_prev_gap(struct address_space *mapping,
pgoff_t index, unsigned long max_scan);
+bool page_cache_range_empty(struct address_space *mapping,
+ pgoff_t index, pgoff_t max);
#define FGP_ACCESSED 0x00000001
#define FGP_LOCK 0x00000002
diff --git a/mm/filemap.c b/mm/filemap.c
index ce74aba33c85..778a551f6713 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1397,6 +1397,32 @@ pgoff_t page_cache_prev_gap(struct address_space *mapping,
}
EXPORT_SYMBOL(page_cache_prev_gap);
+bool page_cache_range_empty(struct address_space *mapping, pgoff_t index,
+ pgoff_t max)
+{
+ struct page *page;
+ XA_STATE(xas, &mapping->pages, index);
+
+ rcu_read_lock();
+ do {
+ page = xas_find(&xas, max);
+ if (xas_retry(&xas, page))
+ continue;
+ /* Shadow entries don't count */
+ if (xa_is_value(page))
+ continue;
+ /*
+ * We don't need to try to pin this page; we're about to
+ * release the RCU lock anyway. It is enough to know that
+ * there was a page here recently.
+ */
+ } while (0);
+ rcu_read_unlock();
+
+ return page != NULL;
+}
+EXPORT_SYMBOL_GPL(page_cache_range_empty);
+
/**
* find_get_entry - find and get a page cache entry
* @mapping: the address_space to search
--
2.16.1
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