Currently, XFS uses BH_PrivateStart for flagging unwritten extent state in a bufferhead. Recently, i found the long standing mmap/unwritten extent conversion bug, and it was to do with partial page invalidation not clearing the unwritten flag from bufferheads attached to the page but beyond EOF. See here for a full explaination: http://oss.sgi.com/archives/xfs/2006-12/msg00196.html The solution I have checked into the XFS dev tree involves duplicating code from block_invalidatepage to clear the unwritten flag from the bufferhead(s), and then calling block_invalidatepage() to do the rest. Christoph suggested that this would be better solved by pushing the unwritten flag into the common buffer head flags and just adding the call to discard_buffer(): http://oss.sgi.com/archives/xfs/2006-12/msg00239.html The following patch makes BH_Unwritten a first class citizen. Patch against 2.6.20-rc3. Signed-Off-By: Dave Chinner <dgc@xxxxxxx> --- fs/buffer.c | 1 + fs/xfs/linux-2.6/xfs_linux.h | 10 ---------- include/linux/buffer_head.h | 2 ++ 3 files changed, 3 insertions(+), 10 deletions(-) Index: linux/fs/buffer.c =================================================================== --- linux.orig/fs/buffer.c 2007-01-08 17:19:49.039465038 +1100 +++ linux/fs/buffer.c 2007-01-08 17:20:43.547898480 +1100 @@ -1439,6 +1439,7 @@ static void discard_buffer(struct buffer clear_buffer_req(bh); clear_buffer_new(bh); clear_buffer_delay(bh); + clear_buffer_unwritten(bh); unlock_buffer(bh); } Index: linux/fs/xfs/linux-2.6/xfs_linux.h =================================================================== --- linux.orig/fs/xfs/linux-2.6/xfs_linux.h 2007-01-08 17:19:32.703335135 +1100 +++ linux/fs/xfs/linux-2.6/xfs_linux.h 2007-01-08 17:19:36.271363508 +1100 @@ -109,16 +109,6 @@ #undef HAVE_PERCPU_SB /* per cpu superblock counters are a 2.6 feature */ #endif -/* - * State flag for unwritten extent buffers. - * - * We need to be able to distinguish between these and delayed - * allocate buffers within XFS. The generic IO path code does - * not need to distinguish - we use the BH_Delay flag for both - * delalloc and these ondisk-uninitialised buffers. - */ -BUFFER_FNS(PrivateStart, unwritten); - #define restricted_chown xfs_params.restrict_chown.val #define irix_sgid_inherit xfs_params.sgid_inherit.val #define irix_symlink_mode xfs_params.symlink_mode.val Index: linux/include/linux/buffer_head.h =================================================================== --- linux.orig/include/linux/buffer_head.h 2007-01-08 17:17:15.118241081 +1100 +++ linux/include/linux/buffer_head.h 2007-01-08 17:18:25.714802453 +1100 @@ -34,6 +34,7 @@ enum bh_state_bits { BH_Write_EIO, /* I/O error on write */ BH_Ordered, /* ordered write */ BH_Eopnotsupp, /* operation not supported (barrier) */ + BH_Unwritten, /* Buffer is allocated on disk but not written */ BH_PrivateStart,/* not a state bit, but the first bit available * for private allocation by other entities @@ -126,6 +127,7 @@ BUFFER_FNS(Boundary, boundary) BUFFER_FNS(Write_EIO, write_io_error) BUFFER_FNS(Ordered, ordered) BUFFER_FNS(Eopnotsupp, eopnotsupp) +BUFFER_FNS(Unwritten, unwritten) #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) #define touch_buffer(bh) mark_page_accessed(bh->b_page) - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
