From 570236dd55e79e8886b45f19cef59ec3fa9d53f6 Mon Sep 17 00:00:00 2001 From: Andrew Deason Date: Tue, 22 Jun 2010 14:36:42 -0500 Subject: [PATCH] ubik: Fix buffers for reading-during-writes If we are reading while a write transaction is in progress, we can encounter a buffer that is dirty if we're on the same site as the writer. Ignore these buffers for readers, since they contain uncommitted changes. Then, when the writer commits, invalidate the resultant duplicate buffer, if one exists. Change-Id: I67e0205362d4c08ea9a8c12104fea8bfe8cbf798 Reviewed-on: http://gerrit.openafs.org/2231 Reviewed-by: Derrick Brashear Tested-by: Derrick Brashear --- src/ubik/disk.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/src/ubik/disk.c b/src/ubik/disk.c index 00ba518ed..611402866 100644 --- a/src/ubik/disk.c +++ b/src/ubik/disk.c @@ -326,6 +326,12 @@ MatchBuffer(struct buffer *buf, int page, afs_int32 fid, if (buf->file != fid) { return 0; } + if (atrans->type == UBIK_READTRANS && buf->dirty) { + /* if 'buf' is dirty, it has uncommitted changes; we do not want to + * see uncommitted changes if we are a read transaction, so skip over + * it. */ + return 0; + } if (buf->dbase != atrans->dbase) { return 0; } @@ -624,6 +630,27 @@ DAbort(struct ubik_trans *atrans) return 0; } +/** + * Invalidate any buffers that are duplicates of abuf. Duplicate buffers + * can appear if a read transaction reads a page that is dirty, then that + * dirty page is synced. The read transaction will skip over the dirty page, + * and create a new buffer, and when the dirty page is synced, it will be + * identical (except for contents) to the read-transaction buffer. + */ +static void +DedupBuffer(struct buffer *abuf) +{ + struct buffer *tb; + for (tb = phTable[pHash(abuf->page)]; tb; tb = tb->hashNext) { + if (tb->page == abuf->page && tb != abuf && tb->file == abuf->file + && tb->dbase == abuf->dbase) { + + tb->file = BADFID; + Dlru(tb); + } + } +} + /*! * \attention DSync() must only be called after DFlush(), due to its interpretation of dirty flag. */ @@ -644,8 +671,10 @@ DSync(struct ubik_trans *atrans) if (tb->dirty == 1) { if (file == BADFID) file = tb->file; - if (file != BADFID && tb->file == file) + if (file != BADFID && tb->file == file) { tb->dirty = 0; + DedupBuffer(tb); + } } } if (file == BADFID) -- 2.39.5