Hi
I have reworte the function truncate_inode_pages. The version
in vanilla pre9-3 does busy waiting in the partial page, with
this version the locking for the partial page and from the
rest of the pages is the same. This make that we have less
special cases. For the rest of pages the function works the
same. The only difference is that version is cleaner IMHO.
Or there are some corner case that I have failed to see?
Comments?
Later, Juan.
I have CC: the linux-fsdevel people, they are the users of
that function, could somebody give me some feedback against
the change?
diff -urN --exclude-from=/home/lfcia/quintela/work/kernel/exclude work/mm/filemap.c
testing/mm/filemap.c
--- work/mm/filemap.c Fri May 12 23:46:46 2000
+++ testing/mm/filemap.c Sun May 14 22:08:45 2000
@@ -146,9 +146,39 @@
spin_unlock(&pagecache_lock);
}
-/*
+static inline void truncate_partial_page(struct page *page, unsigned partial)
+{
+ memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);
+
+ if (page->buffers)
+ block_flushpage(page, partial);
+
+}
+
+static inline void truncate_complete_page(struct page *page)
+{
+ if (!page->buffers || block_flushpage(page, 0))
+ lru_cache_del(page);
+
+ /*
+ * We remove the page from the page cache _after_ we have
+ * destroyed all buffer-cache references to it. Otherwise some
+ * other process might think this inode page is not in the
+ * page cache and creates a buffer-cache alias to it causing
+ * all sorts of fun problems ...
+ */
+ remove_inode_page(page);
+ page_cache_release(page);
+}
+
+/**
+ * truncate_inode_pages - truncate *all* the pages from an offset
+ * @mapping: mapping to truncate
+ * @lstart: offset from with to truncate
+ *
* Truncate the page cache at a set offset, removing the pages
* that are beyond that offset (and zeroing out partial pages).
+ * If any page is locked we wait for it to become unlocked.
*/
void truncate_inode_pages(struct address_space * mapping, loff_t lstart)
{
@@ -168,11 +198,10 @@
page = list_entry(curr, struct page, list);
curr = curr->next;
-
offset = page->index;
- /* page wholly truncated - free it */
- if (offset >= start) {
+ /* Is one of the pages to truncate? */
+ if ((offset >= start) || (partial && (offset + 1) == start)) {
if (TryLockPage(page)) {
page_cache_get(page);
spin_unlock(&pagecache_lock);
@@ -183,22 +212,14 @@
page_cache_get(page);
spin_unlock(&pagecache_lock);
- if (!page->buffers || block_flushpage(page, 0))
- lru_cache_del(page);
-
- /*
- * We remove the page from the page cache
- * _after_ we have destroyed all buffer-cache
- * references to it. Otherwise some other process
- * might think this inode page is not in the
- * page cache and creates a buffer-cache alias
- * to it causing all sorts of fun problems ...
- */
- remove_inode_page(page);
+ if (partial && (offset + 1) == start) {
+ truncate_partial_page(page, partial);
+ partial = 0;
+ } else
+ truncate_complete_page(page);
UnlockPage(page);
page_cache_release(page);
- page_cache_release(page);
/*
* We have done things without the pagecache lock,
@@ -209,37 +230,6 @@
*/
goto repeat;
}
- /*
- * there is only one partial page possible.
- */
- if (!partial)
- continue;
-
- /* and it's the one preceeding the first wholly truncated page */
- if ((offset + 1) != start)
- continue;
-
- /* partial truncate, clear end of page */
- if (TryLockPage(page)) {
- spin_unlock(&pagecache_lock);
- goto repeat;
- }
- page_cache_get(page);
- spin_unlock(&pagecache_lock);
-
- memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);
- if (page->buffers)
- block_flushpage(page, partial);
-
- partial = 0;
-
- /*
- * we have dropped the spinlock so we have to
- * restart.
- */
- UnlockPage(page);
- page_cache_release(page);
- goto repeat;
}
spin_unlock(&pagecache_lock);
}
--
In theory, practice and theory are the same, but in practice they
are different -- Larry McVoy
