Messages in this thread | | | Subject | Possible race between direct IO and JBD? | From | Mingming Cao <> | Date | Fri, 25 Apr 2008 16:38:23 -0700 |
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Hi,
While looking at a bug related to direct IO returns to EIO, after looking at the code, I found there is a window that try_to_free_buffers() from direct IO could race with JBD, which holds the reference to the data buffers before journal_commit_transaction() ensures the data buffers has reached to the disk.
A little more detail: to prepare for direct IO, generic_file_direct_IO() calls invalidate_inode_pages2_range() to invalidate the pages in the cache before performaning direct IO. invalidate_inode_pages2_range() tries to free the buffers via try_to free_buffers(), but sometimes it can't, due to the buffers is possible still on some transaction's t_sync_datalist or t_locked_list waiting for journal_commit_transaction() to process it.
Currently Direct IO simply returns EIO if try_to_free_buffers() finds the buffer is busy, as it has no clue that JBD is referencing it.
Is this a known issue and expected behavior? Any thoughts?
Mingming
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