3 files changed, 108 insertions, 24 deletions

diff --git a/Documentation/ABI/testing/sysfs-fs-ext4 b/Documentation/ABI/testing/sysfs-fs-ext4
new file mode 100644
index 000000000000..4e79074de282
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-fs-ext4
@@ -0,0 +1,81 @@
+What:           /sys/fs/ext4/<disk>/mb_stats
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                 Controls whether the multiblock allocator should
+                 collect statistics, which are shown during the unmount.
+                 1 means to collect statistics, 0 means not to collect
+                 statistics
+
+What:           /sys/fs/ext4/<disk>/mb_group_prealloc
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                The multiblock allocator will round up allocation
+                requests to a multiple of this tuning parameter if the
+                stripe size is not set in the ext4 superblock
+
+What:           /sys/fs/ext4/<disk>/mb_max_to_scan
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                The maximum number of extents the multiblock allocator
+                will search to find the best extent
+
+What:           /sys/fs/ext4/<disk>/mb_min_to_scan
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                The minimum number of extents the multiblock allocator
+                will search to find the best extent
+
+What:           /sys/fs/ext4/<disk>/mb_order2_req
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                Tuning parameter which controls the minimum size for 
+                requests (as a power of 2) where the buddy cache is
+                used
+
+What:           /sys/fs/ext4/<disk>/mb_stream_req
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                Files which have fewer blocks than this tunable
+                parameter will have their blocks allocated out of a
+                block group specific preallocation pool, so that small
+                files are packed closely together.  Each large file
+                 will have its blocks allocated out of its own unique
+                 preallocation pool.
+
+What:           /sys/fs/ext4/<disk>/inode_readahead
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                Tuning parameter which controls the maximum number of
+                inode table blocks that ext4's inode table readahead
+                algorithm will pre-read into the buffer cache
+
+What:           /sys/fs/ext4/<disk>/delayed_allocation_blocks
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                This file is read-only and shows the number of blocks
+                that are dirty in the page cache, but which do not
+                have their location in the filesystem allocated yet.
+
+What:           /sys/fs/ext4/<disk>/lifetime_write_kbytes
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                This file is read-only and shows the number of kilobytes
+                of data that have been written to this filesystem since it was
+                created.
+
+What:           /sys/fs/ext4/<disk>/session_write_kbytes
+Date:           March 2008
+Contact:        "Theodore Ts'o" <tytso@mit.edu>
+Description:
+                This file is read-only and shows the number of
+                kilobytes of data that have been written to this
+                filesystem since it was mounted.
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index cec829bc7291..97882df04865 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -85,7 +85,7 @@ Note: More extensive information for getting started with ext4 can be
 * extent format more robust in face of on-disk corruption due to magics,
 * internal redundancy in tree
 * improved file allocation (multi-block alloc)
-* fix 32000 subdirectory limit
+* lift 32000 subdirectory limit imposed by i_links_count[1]
 * nsec timestamps for mtime, atime, ctime, create time
 * inode version field on disk (NFSv4, Lustre)
 * reduced e2fsck time via uninit_bg feature
@@ -100,6 +100,9 @@ Note: More extensive information for getting started with ext4 can be
 * efficent new ordered mode in JBD2 and ext4(avoid using buffer head to force
   the ordering)
 
+[1] Filesystems with a block size of 1k may see a limit imposed by the
+directory hash tree having a maximum depth of two.
+
 2.2 Candidate features for future inclusion
 
 * Online defrag (patches available but not well tested)
@@ -180,8 +183,8 @@ commit=nrsec	(*)	Ext4 can be told to sync all its data and metadata
                         performance.
 
 barrier=<0|1(*)>        This enables/disables the use of write barriers in
-                        the jbd code.  barrier=0 disables, barrier=1 enables.
-                        This also requires an IO stack which can support
+barrier(*)              the jbd code.  barrier=0 disables, barrier=1 enables.
+nobarrier               This also requires an IO stack which can support
                         barriers, and if jbd gets an error on a barrier
                         write, it will disable again with a warning.
                         Write barriers enforce proper on-disk ordering
@@ -189,6 +192,9 @@ barrier=<0|1(*)>	This enables/disables the use of write barriers in
                         safe to use, at some performance penalty.  If
                         your disks are battery-backed in one way or another,
                         disabling barriers may safely improve performance.
+                        The mount options "barrier" and "nobarrier" can
+                        also be used to enable or disable barriers, for
+                        consistency with other ext4 mount options.
 
 inode_readahead=n       This tuning parameter controls the maximum
                         number of inode table blocks that ext4's inode
@@ -310,6 +316,24 @@ journal_ioprio=prio	The I/O priority (from 0 to 7, where 0 is the
                         a slightly higher priority than the default I/O
                         priority.
 
+auto_da_alloc(*)        Many broken applications don't use fsync() when 
+noauto_da_alloc         replacing existing files via patterns such as
+                        fd = open("foo.new")/write(fd,..)/close(fd)/
+                        rename("foo.new", "foo"), or worse yet,
+                        fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
+                        If auto_da_alloc is enabled, ext4 will detect
+                        the replace-via-rename and replace-via-truncate
+                        patterns and force that any delayed allocation
+                        blocks are allocated such that at the next
+                        journal commit, in the default data=ordered
+                        mode, the data blocks of the new file are forced
+                        to disk before the rename() operation is
+                        commited.  This provides roughly the same level
+                        of guarantees as ext3, and avoids the
+                        "zero-length" problem that can happen when a
+                        system crashes before the delayed allocation
+                        blocks are forced to disk.
+
 Data Mode
 =========
 There are 3 different data modes:
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 830bad7cce0f..efc4fd9f40ce 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -940,27 +940,6 @@ Table 1-10: Files in /proc/fs/ext4/<devname>
  File            Content                                        
  mb_groups       details of multiblock allocator buddy cache of free blocks
  mb_history      multiblock allocation history
- stats           controls whether the multiblock allocator should start
-                 collecting statistics, which are shown during the unmount
- group_prealloc  the multiblock allocator will round up allocation
-                 requests to a multiple of this tuning parameter if the
-                 stripe size is not set in the ext4 superblock
- max_to_scan     The maximum number of extents the multiblock allocator
-                 will search to find the best extent
- min_to_scan     The minimum number of extents the multiblock allocator
-                 will search to find the best extent
- order2_req      Tuning parameter which controls the minimum size for 
-                 requests (as a power of 2) where the buddy cache is
-                 used
- stream_req      Files which have fewer blocks than this tunable
-                 parameter will have their blocks allocated out of a
-                 block group specific preallocation pool, so that small
-                 files are packed closely together.  Each large file
-                 will have its blocks allocated out of its own unique
-                 preallocation pool.
-inode_readahead  Tuning parameter which controls the maximum number of
-                 inode table blocks that ext4's inode table readahead
-                 algorithm will pre-read into the buffer cache
 ..............................................................................