ext4: make the zero-out chunk size tunable

Currently in ext4 the length of zero-out chunk is set to 7 file system
blocks.  But if an inode has uninitailized extents from using
fallocate to preallocate space, and the workload issues many random
writes, this can cause a fragmented extent tree that will
unnecessarily grow the extent tree.

So create a new sysfs tunable, extent_max_zeroout_kb, which controls
the maximum size where blocks will be zeroed out instead of creating a
new uninitialized extent.  The default of this has been sent to 32kb.

CC: Zach Brown <[email protected]>
CC: Andreas Dilger <[email protected]>
Signed-off-by: Zheng Liu <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>

0 files changed, 0 insertions, 0 deletions