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authorLinus Torvalds <torvalds@linux-foundation.org>2009-04-01 10:57:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-01 10:57:49 -0700
commit395d73413c5656c6d7706ae91dcb441f9b7e3074 (patch)
tree7fadabe996f70d7918583fa2312d4fad19397fcb /Documentation/filesystems
parentc226fd659fa7b6a7b038df5ae6856a68514bacde (diff)
parent06705bff9114531a997a7d0c2520bea0f2927410 (diff)
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Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (33 commits) ext4: Regularize mount options ext4: fix locking typo in mballoc which could cause soft lockup hangs ext4: fix typo which causes a memory leak on error path jbd2: Update locking coments ext4: Rename pa_linear to pa_type ext4: add checks of block references for non-extent inodes ext4: Check for an valid i_mode when reading the inode from disk ext4: Use WRITE_SYNC for commits which are caused by fsync() ext4: Add auto_da_alloc mount option ext4: Use struct flex_groups to calculate get_orlov_stats() ext4: Use atomic_t's in struct flex_groups ext4: remove /proc tuning knobs ext4: Add sysfs support ext4: Track lifetime disk writes ext4: Fix discard of inode prealloc space with delayed allocation. ext4: Automatically allocate delay allocated blocks on rename ext4: Automatically allocate delay allocated blocks on close ext4: add EXT4_IOC_ALLOC_DA_BLKS ioctl ext4: Simplify delalloc code by removing mpage_da_writepages() ext4: Save stack space by removing fake buffer heads ...
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/ext4.txt30
-rw-r--r--Documentation/filesystems/proc.txt21
2 files changed, 27 insertions, 24 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index cec829b..97882df 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 830bad7..efc4fd9 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
..............................................................................