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| author | Theodore Ts'o <tytso@mit.edu> | 2012-08-17 17:48:17 +0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2012-08-17 17:48:17 +0400 |
| commit | df981d03eeff7971ac7e6ff37000bfa702327ef1 (patch) | |
| tree | 4e944139b9e45c4af910c517b57f2d9bc7c81a1a /Documentation/filesystems | |
| parent | 01fc48e8929e45e67527200017cff4e74e4ba054 (diff) | |
| download | linux-df981d03eeff7971ac7e6ff37000bfa702327ef1.tar.xz | |
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>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 1b7f9acbcbbe..104322bf378c 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -375,6 +375,16 @@ dioread_nolock locking. If the dioread_nolock option is specified Because of the restrictions this options comprises it is off by default (e.g. dioread_lock). +max_dir_size_kb=n This limits the size of directories so that any + attempt to expand them beyond the specified + limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained + environments, where a very large directory can + cause severe performance problems or even + provoke the Out Of Memory killer. (For example, + if there is only 512mb memory available, a 176mb + directory may seriously cramp the system's style.) + i_version Enable 64-bit inode version support. This option is off by default. |