lkml.org 
[lkml]   [2008]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectPossible race between direct IO and JBD?
From
Date
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



\
 
 \ /
  Last update: 2008-04-26 01:41    [from the cache]
©2003-2011 Jasper Spaans