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-rw-r--r--Documentation/filesystems/ext4.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 34ea4f1fa6e..f7cbf574a87 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -494,6 +494,17 @@ Files in /sys/fs/ext4/<devname>
session_write_kbytes This file is read-only and shows the number of
kilobytes of data that have been written to this
filesystem since it was mounted.
+
+ reserved_clusters This is RW file and contains number of reserved
+ clusters in the file system which will be used
+ in the specific situations to avoid costly
+ zeroout, unexpected ENOSPC, or possible data
+ loss. The default is 2% or 4096 clusters,
+ whichever is smaller and this can be changed
+ however it can never exceed number of clusters
+ in the file system. If there is not enough space
+ for the reserved space when mounting the file
+ mount will _not_ fail.
..............................................................................
Ioctls
@@ -587,6 +598,16 @@ Table of Ext4 specific ioctls
bitmaps and inode table, the userspace tool thus
just passes the new number of blocks.
+EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes
+ (like i_blocks, i_size, i_flags, ...) from
+ the specified inode with inode
+ EXT4_BOOT_LOADER_INO (#5). This is typically
+ used to store a boot loader in a secure part of
+ the filesystem, where it can't be changed by a
+ normal user by accident.
+ The data blocks of the previous boot loader
+ will be associated with the given inode.
+
..............................................................................
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