From 292378edcb408c652e841fdc867fc14f8b4995fa Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Mon, 26 Sep 2016 08:21:28 +1000 Subject: xfs: remote attribute blocks aren't really userdata When adding a new remote attribute, we write the attribute to the new extent before the allocation transaction is committed. This means we cannot reuse busy extents as that violates crash consistency semantics. Hence we currently treat remote attribute extent allocation like userdata because it has the same overwrite ordering constraints as userdata. Unfortunately, this also allows the allocator to incorrectly apply extent size hints to the remote attribute extent allocation. This results in interesting failures, such as transaction block reservation overruns and in-memory inode attribute fork corruption. To fix this, we need to separate the busy extent reuse configuration from the userdata configuration. This changes the definition of XFS_BMAPI_METADATA slightly - it now means that allocation is metadata and reuse of busy extents is acceptible due to the metadata ordering semantics of the journal. If this flag is not set, it means the allocation is that has unordered data writeback, and hence busy extent reuse is not allowed. It no longer implies the allocation is for user data, just that the data write will not be strictly ordered. This matches the semantics for both user data and remote attribute block allocation. As such, This patch changes the "userdata" field to a "datatype" field, and adds a "no busy reuse" flag to the field. When we detect an unordered data extent allocation, we immediately set the no reuse flag. We then set the "user data" flags based on the inode fork we are allocating the extent to. Hence we only set userdata flags on data fork allocations now and consider attribute fork remote extents to be an unordered metadata extent. The result is that remote attribute extents now have the expected allocation semantics, and the data fork allocation behaviour is completely unchanged. It should be noted that there may be other ways to fix this (e.g. use ordered metadata buffers for the remote attribute extent data write) but they are more invasive and difficult to validate both from a design and implementation POV. Hence this patch takes the simple, obvious route to fixing the problem... Reported-and-tested-by: Ross Zwisler Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Dave Chinner --- fs/xfs/libxfs/xfs_bmap.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/xfs/libxfs/xfs_bmap.h') diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h index 254034f96941..05576b7263f6 100644 --- a/fs/xfs/libxfs/xfs_bmap.h +++ b/fs/xfs/libxfs/xfs_bmap.h @@ -54,7 +54,7 @@ struct xfs_bmalloca { bool wasdel; /* replacing a delayed allocation */ bool aeof; /* allocated space at eof */ bool conv; /* overwriting unwritten extents */ - char userdata;/* userdata mask */ + int datatype;/* data type being allocated */ int flags; }; -- cgit v1.2.3