Red Hat Bugzilla – Bug 236277
direct I/O locking confused dlm
Last modified: 2009-09-03 12:51:20 EDT
Description of problem:
We were running a simultaneous streaming direct I/O test case on two nodes, kool
and salem. The dd ran on salem, but kool didn't make any progress. After
killing the dd on salem, the dd on kool remained stuck. Here is the relevant
output from debugfs.
Kool (node 4):
Resource ffff81005faec0c0 Name (len=24) " 2 40a"
Local Copy, Master is node 5
01550021 PR (CW) Master: 02dc0022
Salem (node 5):
Resource ffff81006628ac80 Name (len=24) " 2 40a"
02dc0022 NL (CW) Remote: 4 01550021
1. create file which is 1/2 of memory.
dd if=/dev/urandom bs=1024k count=1024 of=largefile
2. on both nodes, read the file until the I/O speed stabalizes.
for i in `seq 10`; do dd if=largefile of=/dev/null bs=4k; done
3. on both nodes, read the file with direct I/O
for i in `seq 10`; do dd if=largefile of=/dev/null bs=4k iflag=direct; done
Version-Release number of selected component (if applicable):
2.6.21-rc6 + gfs from CVS HEAD
Steps to Reproduce:
*** This bug has been marked as a duplicate of 234086 ***