Commit graph

126 commits

Author SHA1 Message Date
Eric W. Biederman
08cefc7ab8 userns: Convert ext4 to user kuid/kgid where appropriate
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-05-15 14:59:27 -07:00
Heiko Carstens
d4dc462f55 ext4: fix balloc.c printk-format-warning
Get rid of this one:

fs/ext4/balloc.c: In function 'ext4_wait_block_bitmap':
fs/ext4/balloc.c:405:3: warning: format '%llu' expects argument of
  type 'long long unsigned int', but argument 6 has type 'sector_t' [-Wformat]

Happens because sector_t is u64 (unsigned long long) or unsigned long
dependent on CONFIG_64BIT.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-02-20 17:57:24 -05:00
Theodore Ts'o
813e57276f ext4: fix race when setting bitmap_uptodate flag
In ext4_read_{inode,block}_bitmap() we were setting bitmap_uptodate()
before submitting the buffer for read.  The is bad, since we check
bitmap_uptodate() without locking the buffer, and so if another
process is racing with us, it's possible that they will think the
bitmap is uptodate even though the read has not completed yet,
resulting in inodes and blocks potentially getting allocated more than
once if we get really unlucky.

Addresses-Google-Bug: 2828254

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-02-20 17:52:46 -05:00
Eric Sandeen
5f163cc759 ext4: make more symbols static
A couple more functions can reasonably be made static if desired.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-01-04 22:33:28 -05:00
Yongqiang Yang
6e58ad69ef ext4: fix up a undefined error in ext4_free_blocks in debugging code
sbi is not defined, so let ext4_free_blocks use EXT4_SB(sb) instead
when EXT4FS_DEBUG is defined.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
2011-11-21 12:09:19 -05:00
Theodore Ts'o
df55c99dc8 ext4: rename ext4_has_free_blocks() to ext4_has_free_clusters()
Rename the function so it is more clear what is going on.  Also rename
the various variables so it's clearer what's happening.

Also fix a missing blocks to cluster conversion when reading the
number of reserved blocks for root.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:16:51 -04:00
Theodore Ts'o
e7d5f3156e ext4: rename ext4_claim_free_blocks() to ext4_claim_free_clusters()
This function really claims a number of free clusters, not blocks, so
rename it so it's clearer what's going on.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:14:51 -04:00
Theodore Ts'o
cff1dfd767 ext4: rename ext4_free_blocks_after_init() to ext4_free_clusters_after_init()
This function really returns the number of clusters after initializing
an uninitalized block bitmap has been initialized.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:12:51 -04:00
Theodore Ts'o
5dee54372c ext4: rename ext4_count_free_blocks() to ext4_count_free_clusters()
This function really counts the free clusters reported in the block
group descriptors, so rename it to reduce confusion.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:10:51 -04:00
Theodore Ts'o
021b65bb1e ext4: Rename ext4_free_blks_{count,set}() to refer to clusters
The field bg_free_blocks_count_{lo,high} in the block group
descriptor has been repurposed to hold the number of free clusters for
bigalloc functions.  So rename the functions so it makes it easier to
read and audit the block allocation and block freeing code.

Note: at this point in bigalloc development we doesn't support
online resize, so this also makes it really obvious all of the places
we need to fix up to add support for online resize.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:08:51 -04:00
Aditya Kali
7b415bf60f ext4: Fix bigalloc quota accounting and i_blocks value
With bigalloc changes, the i_blocks value was not correctly set (it was still
set to number of blocks being used, but in case of bigalloc, we want i_blocks
to represent the number of clusters being used). Since the quota subsystem sets
the i_blocks value, this patch fixes the quota accounting and makes sure that
the i_blocks value is set correctly.

Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 19:04:51 -04:00
Theodore Ts'o
5704265188 ext4: convert s_{dirty,free}blocks_counter to s_{dirty,free}clusters_counter
Convert the percpu counters s_dirtyblocks_counter and
s_freeblocks_counter in struct ext4_super_info to be
s_dirtyclusters_counter and s_freeclusters_counter.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 18:56:51 -04:00
Theodore Ts'o
3212a80a58 ext4: convert block group-relative offsets to use clusters
Certain parts of the ext4 code base, primarily in mballoc.c, use a
block group number and offset from the beginning of the block group.
This offset is invariably used to index into the allocation bitmap, so
change the offset to be denominated in units of clusters.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 18:46:51 -04:00
Theodore Ts'o
d5b8f31007 ext4: bigalloc changes to block bitmap initialization functions
Add bigalloc support to ext4_init_block_bitmap() and
ext4_free_blocks_after_init().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 18:44:51 -04:00
Theodore Ts'o
fd034a84e1 ext4: split out ext4_free_blocks_after_init()
The function ext4_free_blocks_after_init() used to be a #define of
ext4_init_block_bitmap().  This actually made it difficult to
understand how the function worked, and made it hard make changes to
support clusters.  So as an initial cleanup, I've separated out the
functionality of initializing block bitmap from calculating the number
of free blocks in the new block group.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 18:42:51 -04:00
Theodore Ts'o
49f7f9af4b ext4: factor out block group accounting into functions
This makes it easier to understand how ext4_init_block_bitmap() works,
and it will assist when we split out ext4_free_blocks_after_init() in
the next commit.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-09-09 18:40:51 -04:00
Eric Sandeen
f86186b44b ext4: refactor duplicated block placement code
I found that ext4_ext_find_goal() and ext4_find_near()
share the same code for returning a coloured start block
based on i_block_group.

We can refactor this into a common function so that they
don't diverge in the future.

Thanks to adilger for suggesting the new function name.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-06-28 10:01:31 -04:00
Allison Henderson
55f020db66 ext4: add flag to ext4_has_free_blocks
This patch adds an allocation request flag to the ext4_has_free_blocks
function which enables the use of reserved blocks.  This will allow a
punch hole to proceed even if the disk is full.  Punching a hole may
require additional blocks to first split the extents.

Because ext4_has_free_blocks is a low level function, the flag needs
to be passed down through several functions listed below:

ext4_ext_insert_extent
ext4_ext_create_new_leaf
ext4_ext_grow_indepth
ext4_ext_split
ext4_ext_new_meta_block
ext4_mb_new_blocks
ext4_claim_free_blocks
ext4_has_free_blocks

[ext4 punch hole patch series 1/5 v7]

Signed-off-by: Allison Henderson <achender@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Mingming Cao <cmm@us.ibm.com>
2011-05-25 07:41:26 -04:00
Amir Goldstein
2846e82004 ext4: move ext4_add_groupblocks() to mballoc.c
In preparation for the next patch, the function ext4_add_groupblocks()
is moved to mballoc.c, where it could use some static functions.

Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-05-09 10:46:41 -04:00
Shaohua Li
dc2070a241 ext4: remove dead code in ext4_has_free_blocks()
percpu_counter_sum_positive() never returns a negative value.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-05-01 18:11:18 -04:00
Lucas De Marchi
25985edced Fix common misspellings
Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-03-31 11:26:23 -03:00
Jiaying Zhang
0562e0bad4 ext4: add more tracepoints and use dev_t in the trace buffer
- Add more ext4 tracepoints.
- Change ext4 tracepoints to use dev_t field with MAJOR/MINOR macros
so that we can save 4 bytes in the ring buffer on some platforms.
- Add sync_mode to ext4_da_writepages, ext4_da_write_pages, and
ext4_da_writepages_result tracepoints. Also remove for_reclaim
field from ext4_da_writepages since it is usually not very useful.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-03-21 21:38:05 -04:00
Theodore Ts'o
f232109773 ext4: replace i_delalloc_reserved_flag with EXT4_STATE_DELALLOC_RESERVED
Remove the short element i_delalloc_reserved_flag from the
ext4_inode_info structure and replace it a new bit in i_state_flags.
Since we have an ext4_inode_info for every ext4 inode cached in the
inode cache, any savings we can produce here is a very good thing from
a memory utilization perspective.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-01-10 12:12:36 -05:00
Theodore Ts'o
61d08673de ext4: rename mark_bitmap_end() to ext4_mark_bitmap_end()
Fix a namespace leak from fs/ext4

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:15 -04:00
Theodore Ts'o
1f109d5a17 ext4: make various ext4 functions be static
These functions have no need to be exported beyond file context.

No functions needed to be moved for this commit; just some function
declarations changed to be static and removed from header files.

(A similar patch was submitted by Eric Sandeen, but I wanted to handle
code movement in separate patches to make sure code changes didn't
accidentally get dropped.)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o
a0375156ca ext4: Clean up s_dirt handling
We don't need to set s_dirt in most of the ext4 code when journaling
is enabled.  In ext3/4 some of the summary statistics for # of free
inodes, blocks, and directories are calculated from the per-block
group statistics when the file system is mounted or unmounted.  As a
result the superblock doesn't have to be updated, either via the
journal or by setting s_dirt.  There are a few exceptions, most
notably when resizing the file system, where the superblock needs to
be modified --- and in that case it should be done as a journalled
operation if possible, and s_dirt set only in no-journal mode.

This patch will optimize out some unneeded disk writes when using ext4
with a journal.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-06-11 23:14:04 -04:00
Eric Sandeen
72b8ab9dde ext4: don't use quota reservation for speculative metadata
Because we can badly over-reserve metadata when we
calculate worst-case, it complicates things for quota, since
we must reserve and then claim later, retry on EDQUOT, etc.
Quota is also a generally smaller pool than fs free blocks,
so this over-reservation hurts more, and more often.

I'm of the opinion that it's not the worst thing to allow
metadata to push a user slightly over quota.  This simplifies
the code and avoids the false quota rejections that result
from worst-case speculation.

This patch stops the speculative quota-charging for
worst-case metadata requirements, and just charges quota
when the blocks are allocated at writeout.  It also is
able to remove the try-again loop on EDQUOT.

This patch has been tested indirectly by running the xfstests
suite with a hack to mount & enable quota prior to the test.

I also did a more specific test of fragmenting freespace
and then doing a large delalloc write under quota; quota
stopped me at the right amount of file IO, and then the
writeout generated enough metadata (due to the fragmentation)
that it put me slightly over quota, as expected.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-05-16 11:00:00 -04:00
Akinobu Mita
731eb1a03a ext4: consolidate in_range() definitions
There are duplicate macro definitions of in_range() in mballoc.h and
balloc.c.  This consolidates these two definitions into ext4.h, and
changes extents.c to use in_range() as well.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@sun.com>
2010-03-03 23:55:01 -05:00
Akinobu Mita
5661bd6861 ext4: cleanup to use ext4_group_first_block_no()
This is a cleanup and simplification patch which takes some open-coded
calculations to calculate the first block number of a group and
converts them to use the (already defined) ext4_group_first_block_no()
function.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@sun.com>
2010-03-03 23:53:39 -05:00
Eric Sandeen
12062dddda ext4: move __func__ into a macro for ext4_warning, ext4_error
Just a pet peeve of mine; we had a mishash of calls with either __func__
or "function_name" and the latter tends to get out of sync.

I think it's easier to just hide the __func__ in a macro, and it'll
be consistent from then on.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-02-15 14:19:27 -05:00
Theodore Ts'o
4433871130 ext4: fold ext4_free_blocks() and ext4_mb_free_blocks()
ext4_mb_free_blocks() is only called by ext4_free_blocks(), and the
latter function doesn't really do much.  So merge the two functions
together, such that ext4_free_blocks() is now found in
fs/ext4/mballoc.c.  This saves about 200 bytes of compiled text space.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-11-22 07:44:56 -05:00
Theodore Ts'o
8dadb198cb ext4: fix uninit block bitmap initialization when s_meta_first_bg is non-zero
The number of old-style block group descriptor blocks is
s_meta_first_bg when the meta_bg feature flag is set.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
2009-11-23 07:24:38 -05:00
Eric Sandeen
0373130d5b ext4: open-code ext4_mb_update_group_info
ext4_mb_update_group_info is only called in one place, and it's
extremely simple.  There's no reason to have it in a separate function
in a separate file as far as I can tell, it just obfuscates what's
really going on.

Perhaps it was intended to keep the grp->bb_* manipulation local to
mballoc.c but we're already accessing other grp-> fields in balloc.c
directly so this seems ok.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-08-17 23:51:29 -04:00
Aneesh Kumar K.V
955ce5f5be ext4: Convert ext4_lock_group to use sb_bgl_lock
We have sb_bgl_lock() and ext4_group_info.bb_state
bit spinlock to protech group information. The later is only
used within mballoc code. Consolidate them to use sb_bgl_lock().
This makes the mballoc.c code much simpler and also avoid
confusion with two locks protecting same info.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-05-02 20:35:09 -04:00
Theodore Ts'o
bb23c20a85 ext4: Move fs/ext4/group.h into ext4.h
Move the function prototypes in group.h into ext4.h so they are all
defined in one place.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-05-01 19:44:44 -04:00
Theodore Ts'o
8df9675f8b ext4: Avoid races caused by on-line resizing and SMP memory reordering
Ext4's on-line resizing adds a new block group and then, only at the
last step adjusts s_groups_count.  However, it's possible on SMP
systems that another CPU could see the updated the s_group_count and
not see the newly initialized data structures for the just-added block
group.  For this reason, it's important to insert a SMP read barrier
after reading s_groups_count and before reading any (for example) the
new block group descriptors allowed by the increased value of
s_groups_count.

Unfortunately, we rather blatently violate this locking protocol
documented in fs/ext4/resize.c.  Fortunately, (1) on-line resizes
happen relatively rarely, and (2) it seems rare that the filesystem
code will immediately try to use just-added block group before any
memory ordering issues resolve themselves.  So apparently problems
here are relatively hard to hit, since ext3 has been vulnerable to the
same issue for years with no one apparently complaining.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-05-01 08:50:38 -04:00
Theodore Ts'o
9f24e4208f ext4: Use atomic_t's in struct flex_groups
Reduce pressure on the sb_bgl_lock family of locks by using atomic_t's
to track the number of free blocks and inodes in each flex_group.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-03-04 19:09:10 -05:00
Theodore Ts'o
e187c6588d ext4: remove call to ext4_group_desc() in ext4_group_used_meta_blocks()
The static function ext4_group_used_meta_blocks() only has one caller,
who already has access to the block group's group descriptor.  So it's
better to have ext4_init_block_bitmap() pass the group descriptor to
ext4_group_used_meta_blocks(), so it doesn't need to call
ext4_group_desc().  Previously this function did not check if
ext4_group_desc() returned NULL due to an error, potentially causing a
kernel OOPS report.  This avoids the issue entirely.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-02-06 16:23:37 -05:00
Jan Kara
a269eb1829 ext4: Use lowercase names of quota functions
Use lowercase names of quota functions instead of old uppercase ones.

Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mingming Cao <cmm@us.ibm.com>
CC: linux-ext4@vger.kernel.org
2009-03-26 02:18:36 +01:00
Eric Sandeen
8f64b32eb7 ext4: don't call jbd2_journal_force_commit_nested without journal
Running without a journal, I oopsed when I ran out of space,
because we called jbd2_journal_force_commit_nested() from
ext4_should_retry_alloc() without a journal.

This should take care of it, I think.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-02-26 00:57:35 -05:00
Thadeu Lima de Souza Cascardo
9fd9784c91 ext4: Fix building with EXT4FS_DEBUG
When bg_free_blocks_count was renamed to bg_free_blocks_count_lo in
560671a0, its uses under EXT4FS_DEBUG were not changed to the helper
ext4_free_blks_count.

Another commit, 498e5f24, also did not change everything needed under
EXT4FS_DEBUG, thus making it spill some warnings related to printing
format.

This commit fixes both issues and makes ext4 build again when
EXT4FS_DEBUG is enabled.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-26 19:26:26 -05:00
Aneesh Kumar K.V
2ccb5fb9f1 ext4: Use new buffer_head flag to check uninit group bitmaps initialization
For uninit block group, the on-disk bitmap is not initialized. That
implies we cannot depend on the uptodate flag on the bitmap
buffer_head to find bitmap validity.  Use a new buffer_head flag which
would be set after we properly initialize the bitmap.  This also
prevents (re-)initializing the uninit group bitmap every time we call 
ext4_read_block_bitmap().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
2009-01-05 21:49:55 -05:00
Aneesh Kumar K.V
3300beda52 ext4: code cleanup
Rename some variables.  We also unlock locks in the reverse order we
acquired as a part of cleanup.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-03 22:33:39 -05:00
Aneesh Kumar K.V
560671a0d3 ext4: Use high 16 bits of the block group descriptor's free counts fields
Rename the lower bits with suffix _lo and add helper
to access the values. Also rename bg_itable_unused_hi
to bg_pad as in e2fsprogs.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-05 22:20:24 -05:00
Aneesh Kumar K.V
920313a726 ext4: Use EXT4_GROUP_INFO_NEED_INIT_BIT during resize
The new groups added during resize are flagged as
need_init group. Make sure we properly initialize these
groups. When we have block size < page size and we are adding
new groups the page may still be marked uptodate even though
we haven't initialized the group. While forcing the init
of buddy cache we need to make sure other groups part of the
same page of buddy cache is not using the cache.
group_info->alloc_sem is added to ensure the same.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
cc: stable@kernel.org
2009-01-05 21:36:19 -05:00
Aneesh Kumar K.V
e21675d4b6 ext4: Add blocks added during resize to bitmap
With this change new blocks added during resize
are marked as free in the block bitmap and the
group is flagged with EXT4_GROUP_INFO_NEED_INIT_BIT
flag.  This makes sure when mballoc tries to allocate
blocks from the new group we would reload the
buddy information using the bitmap present in the disk.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
2009-01-05 21:36:02 -05:00
Theodore Ts'o
498e5f2415 ext4: Change unsigned long to unsigned int
Convert the unsigned longs that are most responsible for bloating the
stack usage on 64-bit systems.

Nearly all places in the ext3/4 code which uses "unsigned long" is
probably a bug, since on 32-bit systems a ulong a 32-bits, which means
we are wasting stack space on 64-bit systems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2008-11-05 00:14:04 -05:00
Theodore Ts'o
a9df9a4910 ext4: Make ext4_group_t be an unsigned int
Nearly all places in the ext3/4 code which uses "unsigned long" is
probably a bug, since on 32-bit systems a ulong a 32-bits, which means
we are wasting stack space on 64-bit systems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-05 22:18:16 -05:00
Theodore Ts'o
fde4d95ad8 ext4: remove extraneous newlines from calls to ext4_error() and ext4_warning()
This removes annoying blank syslog entries emitted by ext4_error() or
ext4_warning(), since these functions add their own newline.

Signed-off-by: Nick Warne <nick@ukfsn.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-05 22:17:35 -05:00
Frank Mayhar
0390131ba8 ext4: Allow ext4 to run without a journal
A few weeks ago I posted a patch for discussion that allowed ext4 to run
without a journal.  Since that time I've integrated the excellent
comments from Andreas and fixed several serious bugs.  We're currently
running with this patch and generating some performance numbers against
both ext2 (with backported reservations code) and ext4 with and without
a journal.  It just so happens that running without a journal is
slightly faster for most everything.

We did
	iozone -T -t 4 s 2g -r 256k -T -I -i0 -i1 -i2

which creates 4 threads, each of which create and do reads and writes on
a 2G file, with a buffer size of 256K, using O_DIRECT for all file opens
to bypass the page cache.  Results:

                     ext2        ext4, default   ext4, no journal
  initial writes   13.0 MB/s        15.4 MB/s          15.7 MB/s
  rewrites         13.1 MB/s        15.6 MB/s          15.9 MB/s
  reads            15.2 MB/s        16.9 MB/s          17.2 MB/s
  re-reads         15.3 MB/s        16.9 MB/s          17.2 MB/s
  random readers    5.6 MB/s         5.6 MB/s           5.7 MB/s
  random writers    5.1 MB/s         5.3 MB/s           5.4 MB/s 

So it seems that, so far, this was a useful exercise.

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-07 00:06:22 -05:00