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[PATCH 6/9] xfs: switch to NOFS allocation under i_lock in xfs_buf_assoc

To: xfs@xxxxxxxxxxx
Subject: [PATCH 6/9] xfs: switch to NOFS allocation under i_lock in xfs_buf_associate_memory
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Sat, 18 Jul 2009 18:14:58 -0400
Cc: sage@xxxxxxxxxxxx
References: <20090718221452.594956000@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: quilt/0.47-1
xfs_buf_associate_memory is used for setting up the spare buffer for the
log wrap case in xlog_sync which can happen under i_lock when called from
xfs_fsync. The i_lock mutex is taken in reclaim context so all allocations
under it must avoid recursions into the filesystem.  There are a couple
more uses of xfs_buf_associate_memory in the log recovery code that are
also affected by this, but I'd rather keep the code simple than passing on
a gfp_mask argument.  Longer term we should just stop requiring the memoery
allocation in xlog_sync by some smaller rework of the buffer layer.

Reported by the new reclaim context tracing in lockdep.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Index: linux-2.6/fs/xfs/linux-2.6/xfs_buf.c
--- linux-2.6.orig/fs/xfs/linux-2.6/xfs_buf.c   2009-07-18 18:26:07.359681952 
+++ linux-2.6/fs/xfs/linux-2.6/xfs_buf.c        2009-07-18 18:26:53.531658254 
@@ -770,7 +770,7 @@ xfs_buf_associate_memory(
        bp->b_pages = NULL;
        bp->b_addr = mem;
-       rval = _xfs_buf_get_pages(bp, page_count, 0);
+       rval = _xfs_buf_get_pages(bp, page_count, XBF_DONT_BLOCK);
        if (rval)
                return rval;

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