xfs: kill XBF_DONTBLOCK

Just about all callers of xfs_buf_read() and xfs_buf_get() use XBF_DONTBLOCK.
This is used to make memory allocation use GFP_NOFS rather than GFP_KERNEL to
avoid recursion through memory reclaim back into the filesystem.

All the blocking get calls in growfs occur inside a transaction, even though
they are no part of the transaction, so all allocation will be GFP_NOFS due to
the task flag PF_TRANS being set. The blocking read calls occur during log
recovery, so they will probably be unaffected by converting to GFP_NOFS
allocations.

Hence make XBF_DONTBLOCK behaviour always occur for buffers and kill the flag.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 8f99c77..6c18745 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -82,7 +82,7 @@
 		byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 
 		bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt),
-				  XBF_MAPPED | XBF_DONT_BLOCK);
+				  XBF_MAPPED);
 		if (!bp)
 			return XFS_ERROR(ENOMEM);
 		error = bp->b_error;
@@ -1966,7 +1966,7 @@
 
 	bp = xfs_buf_get_uncached(XFS_IS_REALTIME_INODE(ip) ?
 					mp->m_rtdev_targp : mp->m_ddev_targp,
-				BTOBB(mp->m_sb.sb_blocksize), XBF_DONT_BLOCK);
+				  BTOBB(mp->m_sb.sb_blocksize), 0);
 	if (!bp)
 		return XFS_ERROR(ENOMEM);