[XFS] Fix memory corruption with small buffer reads

[linux-2.6-omap-h63xx.git] / fs / xfs / linux-2.6 / xfs_buf.h

diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h
index b5908a34b15d80916ac7ce307a76f02e319bcf73..f948ec7ba9a4300b2089ff1a4b8b4f3c2dd70ff4 100644 (file)
--- a/fs/xfs/linux-2.6/xfs_buf.h
+++ b/fs/xfs/linux-2.6/xfs_buf.h
@@ -66,6 +66,25 @@ typedef enum {
        _XBF_PAGES = (1 << 18),     /* backed by refcounted pages          */
        _XBF_RUN_QUEUES = (1 << 19),/* run block device task queue         */
        _XBF_DELWRI_Q = (1 << 21),   /* buffer on delwri queue             */
+
+       /*
+        * Special flag for supporting metadata blocks smaller than a FSB.
+        *
+        * In this case we can have multiple xfs_buf_t on a single page and
+        * need to lock out concurrent xfs_buf_t readers as they only
+        * serialise access to the buffer.
+        *
+        * If the FSB size >= PAGE_CACHE_SIZE case, we have no serialisation
+        * between reads of the page. Hence we can have one thread read the
+        * page and modify it, but then race with another thread that thinks
+        * the page is not up-to-date and hence reads it again.
+        *
+        * The result is that the first modifcation to the page is lost.
+        * This sort of AGF/AGI reading race can happen when unlinking inodes
+        * that require truncation and results in the AGI unlinked list
+        * modifications being lost.
+        */
+       _XBF_PAGE_LOCKED = (1 << 22),
 } xfs_buf_flags_t;
 
 typedef enum {
@@ -143,7 +162,6 @@ typedef struct xfs_buf {
        void                    *b_fspriv2;
        void                    *b_fspriv3;
        unsigned short          b_error;        /* error code on I/O */
-       unsigned short          b_locked;       /* page array is locked */
        unsigned int            b_page_count;   /* size of page array */
        unsigned int            b_offset;       /* page offset in first page */
        struct page             **b_pages;      /* array of page pointers */
@@ -388,11 +406,15 @@ static inline int XFS_bwrite(xfs_buf_t *bp)
        return error;
 }
 
-static inline int xfs_bdwrite(void *mp, xfs_buf_t *bp)
+/*
+ * No error can be returned from xfs_buf_iostart for delwri
+ * buffers as they are queued and no I/O is issued.
+ */
+static inline void xfs_bdwrite(void *mp, xfs_buf_t *bp)
 {
        bp->b_strat = xfs_bdstrat_cb;
        bp->b_fspriv3 = mp;
-       return xfs_buf_iostart(bp, XBF_DELWRI | XBF_ASYNC);
+       (void)xfs_buf_iostart(bp, XBF_DELWRI | XBF_ASYNC);
 }
 
 #define XFS_bdstrat(bp) xfs_buf_iorequest(bp)