tree 01bcc80ee26a9cc25df9b9a215081943f3fcbd6c
parent d794bf8e0936dce45104565cd48c571061f4c1e3
author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> 1234626178 -0500
committer Theodore Ts'o <tytso@mit.edu> 1234626178 -0500

ext4: Implement range_cyclic in ext4_da_writepages instead of write_cache_pages

With delayed allocation we lock the page in write_cache_pages() and
try to build an in memory extent of contiguous blocks.  This is needed
so that we can get large contiguous blocks request.  If range_cyclic
mode is enabled, write_cache_pages() will loop back to the 0 index if
no I/O has been done yet, and try to start writing from the beginning
of the range.  That causes an attempt to take the page lock of lower
index page while holding the page lock of higher index page, which can
cause a dead lock with another writeback thread.

The solution is to implement the range_cyclic behavior in
ext4_da_writepages() instead.

http://bugzilla.kernel.org/show_bug.cgi?id=12579

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>