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authorZach Brown <zach.brown@oracle.com>2005-12-15 14:28:17 -0800
committerJoel Becker <joel.becker@oracle.com>2006-01-03 11:45:42 -0800
commit994fc28c7b1e697ac56befe4aecabf23f0689f46 (patch)
treeda36d162e9bd077e9b5be385b28e2db90475c263 /include/linux/fs.h
parent7063fbf2261194f72ee75afca67b3b38b554b5fa (diff)
[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>
Diffstat (limited to 'include/linux/fs.h')
-rw-r--r--include/linux/fs.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cc35b6ac778d..ed9a41a71e8b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -302,6 +302,37 @@ struct iattr {
*/
#include <linux/quota.h>
+/**
+ * enum positive_aop_returns - aop return codes with specific semantics
+ *
+ * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
+ * completed, that the page is still locked, and
+ * should be considered active. The VM uses this hint
+ * to return the page to the active list -- it won't
+ * be a candidate for writeback again in the near
+ * future. Other callers must be careful to unlock
+ * the page if they get this return. Returned by
+ * writepage();
+ *
+ * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
+ * unlocked it and the page might have been truncated.
+ * The caller should back up to acquiring a new page and
+ * trying again. The aop will be taking reasonable
+ * precautions not to livelock. If the caller held a page
+ * reference, it should drop it before retrying. Returned
+ * by readpage(), prepare_write(), and commit_write().
+ *
+ * address_space_operation functions return these large constants to indicate
+ * special semantics to the caller. These are much larger than the bytes in a
+ * page to allow for functions that return the number of bytes operated on in a
+ * given page.
+ */
+
+enum positive_aop_returns {
+ AOP_WRITEPAGE_ACTIVATE = 0x80000,
+ AOP_TRUNCATED_PAGE = 0x80001,
+};
+
/*
* oh the beauties of C type declarations.
*/