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ocfs2: record UNWRITTEN extents when populate write desc
To support direct io in ocfs2_write_begin_nolock & ocfs2_write_end_nolock. There is still one issue in the direct write procedure. phase 1: alloc extent with UNWRITTEN flag phase 2: submit direct data to disk, add zero page to page cache phase 3: clear UNWRITTEN flag when data has been written to disk When there are 2 direct write A(0~3KB),B(4~7KB) writing to the same cluster 0~7KB (cluster size 8KB). Write request A arrive phase 2 first, it will zero the region (4~7KB). Before request A enter to phase 3, request B arrive phase 2, it will zero region (0~3KB). This is just like request B steps request A. To resolve this issue, we should let request B knows this cluster is already under zero, to prevent it from steps the previous write request. This patch will add function ocfs2_unwritten_check() to do this job. It will record all clusters that are under direct write(it will be recorded in the 'ip_unwritten_list' member of inode info), and prevent the later direct write writing to the same cluster to do the zero work again. Signed-off-by: Ryan Ding <[email protected]> Reviewed-by: Junxiao Bi <[email protected]> Cc: Joseph Qi <[email protected]> Cc: Mark Fasheh <[email protected]> Cc: Joel Becker <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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