tree 34b841b58e19de0bd43d8780e8635c25ef6eb37b
parent 972fbf779832e5ad15effa7712789aeff9224c37
author Mingming Cao <cmm@us.ibm.com> 1224386876 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1224517957 -0700

ext3: fix ext3 block reservation early ENOSPC issue

We could run into ENOSPC error on ext3, even when there is free blocks on
the filesystem.

The problem is triggered in the case the goal block group has 0 free
blocks , and the rest block groups are skipped due to the check of
"free_blocks < windowsz/2".  Current code could fall back to non
reservation allocation to prevent early ENOSPC after examing all the block
groups with reservation on , but this code was bypassed if the reservation
window is turned off already, which is true in this case.

This patch fixed two issues:
1) We don't need to turn off block reservation if the goal block group has
0 free blocks left and continue search for the rest of block groups.

Current code the intention is to turn off the block reservation if the
goal allocation group has a few (some) free blocks left (not enough for
make the desired reservation window),to try to allocation in the goal
block group, to get better locality.  But if the goal blocks have 0 free
blocks, it should leave the block reservation on, and continues search for
the next block groups,rather than turn off block reservation completely.

2) we don't need to check the window size if the block reservation is off.

The problem was originally found and fixed in ext4.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>