From df981d03eeff7971ac7e6ff37000bfa702327ef1 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Fri, 17 Aug 2012 09:48:17 -0400
Subject: ext4: add max_dir_size_kb mount option
Very large directories can cause significant performance problems, or
perhaps even invoke the OOM killer, if the process is running in a
highly constrained memory environment (whether it is VM's with a small
amount of memory or in a small memory cgroup).
So it is useful, in cloud server/data center environments, to be able
to set a filesystem-wide cap on the maximum size of a directory, to
ensure that directories never get larger than a sane size. We do this
via a new mount option, max_dir_size_kb. If there is an attempt to
grow the directory larger than max_dir_size_kb, the system call will
return ENOSPC instead.
Google-Bug-Id: 6863013
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/ext4.h | 1 +
1 file changed, 1 insertion(+)
(limited to 'fs/ext4/ext4.h')
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index c3411d4ce2da..7c0841ecde6c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1243,6 +1243,7 @@ struct ext4_sb_info {
unsigned int s_mb_order2_reqs;
unsigned int s_mb_group_prealloc;
unsigned int s_max_writeback_mb_bump;
+ unsigned int s_max_dir_size_kb;
/* where last allocation was done - for stream allocation */
unsigned long s_mb_last_group;
unsigned long s_mb_last_start;
--
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