[PATCH] add AOP_TRUNCATED_PAGE, prepend AOP_ to WRITEPAGE_ACTIVATE
readpage(), prepare_write(), and commit_write() callers are updated to
understand the special return code AOP_TRUNCATED_PAGE in the style of
writepage() and WRITEPAGE_ACTIVATE. AOP_TRUNCATED_PAGE tells the caller that
the callee has unlocked the page and that the operation should be tried again
with a new page. OCFS2 uses this to detect and work around a lock inversion in
its aop methods. There should be no change in behaviour for methods that don't
return AOP_TRUNCATED_PAGE.
WRITEPAGE_ACTIVATE is also prepended with AOP_ for consistency and they are
made enums so that kerneldoc can be used to document their semantics.
Signed-off-by: Zach Brown <zach.brown@oracle.com>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 96c664a..a452b13 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -213,7 +213,7 @@
struct address_space_operations *aops = mapping->a_ops;
pgoff_t index;
unsigned offset, bv_offs;
- int len, ret = 0;
+ int len, ret;
down(&mapping->host->i_sem);
index = pos >> PAGE_CACHE_SHIFT;
@@ -232,9 +232,15 @@
page = grab_cache_page(mapping, index);
if (unlikely(!page))
goto fail;
- if (unlikely(aops->prepare_write(file, page, offset,
- offset + size)))
+ ret = aops->prepare_write(file, page, offset,
+ offset + size);
+ if (unlikely(ret)) {
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ continue;
+ }
goto unlock;
+ }
transfer_result = lo_do_transfer(lo, WRITE, page, offset,
bvec->bv_page, bv_offs, size, IV);
if (unlikely(transfer_result)) {
@@ -251,9 +257,15 @@
kunmap_atomic(kaddr, KM_USER0);
}
flush_dcache_page(page);
- if (unlikely(aops->commit_write(file, page, offset,
- offset + size)))
+ ret = aops->commit_write(file, page, offset,
+ offset + size);
+ if (unlikely(ret)) {
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ continue;
+ }
goto unlock;
+ }
if (unlikely(transfer_result))
goto unlock;
bv_offs += size;
@@ -264,6 +276,7 @@
unlock_page(page);
page_cache_release(page);
}
+ ret = 0;
out:
up(&mapping->host->i_sem);
return ret;