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authorIngo Molnar <mingo@elte.hu>2008-06-23 11:53:03 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-23 11:53:03 +0200
commit009b9fc98ddd83f9139fdabb12c0d7a8535d5421 (patch)
treef7d3e182407d2ebe50a9b8db6361ac910027a1cf /fs/xfs/linux-2.6/xfs_buf.h
parent3711ccb07b7f0a13f4f1aa16a8fdca9c930f21ca (diff)
parent481c5346d0981940ee63037eb53e4e37b0735c10 (diff)
Merge branch 'linus' into x86/threadinfotip-x86-threadinfo-2008-06-23_09.53_Mon
Diffstat (limited to 'fs/xfs/linux-2.6/xfs_buf.h')
-rw-r--r--fs/xfs/linux-2.6/xfs_buf.h19
1 files changed, 19 insertions, 0 deletions
diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h
index 841d7883528d..f948ec7ba9a4 100644
--- 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 {