linux.git/fs/ext4/ialloc.c, branch v2.6.29-rc2

ext4: Remove "extents" mount option

2009-01-06T19:53:16+00:00

This mount option is largely superfluous, and in fact the way it was
implemented was buggy; if a filesystem which did not have the extents
feature flag was mounted -o extents, the filesystem would attempt to
create and use extents-based file even though the extents feature flag
was not eabled.  The simplest thing to do is to nuke the mount option
entirely.  It's not all that useful to force the non-creation of new
extent-based files if the filesystem can support it.

Signed-off-by: "Theodore Ts'o"

ext4: Add markers for better debuggability

2009-01-04T01:03:21+00:00

Signed-off-by: "Theodore Ts'o"

ext4: mark the blocks/inode bitmap beyond end of group as used

2009-01-06T02:46:04+00:00

We need to mark the block/inode bitmap beyond the end of the group
with '1'.

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: "Theodore Ts'o" 
Cc: stable@kernel.org

ext4: Use new buffer_head flag to check uninit group bitmaps initialization

2009-01-06T02:49:55+00:00

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 
Signed-off-by: "Theodore Ts'o" 
Cc: stable@kernel.org

ext4: Fix the race between read_inode_bitmap() and ext4_new_inode()

2009-01-06T02:38:14+00:00

We need to make sure we update the inode bitmap and clear
EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held, since
ext4_read_inode_bitmap() looks at EXT4_BG_INODE_UNINIT to decide
whether to initialize the inode bitmap each time it is called.
(introduced by commit c806e68f.)

ext4_read_inode_bitmap does:

spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));
if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
	ext4_init_inode_bitmap(sb, bh, block_group, desc);

and ext4_new_inode does
if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group),
                   ino, inode_bitmap_bh->b_data))
		   ......
		   ...
spin_lock(sb_bgl_lock(sbi, group));

gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
i.e., on allocation we update the bitmap then we take the sb_bgl_lock
and clear the EXT4_BG_INODE_UNINIT flag. What can happen is a
parallel ext4_read_inode_bitmap can zero out the bitmap in between
the above ext4_set_bit_atomic and spin_lock(sb_bg_lock..)

The race results in below user visible errors
EXT4-fs error (device sdb1): ext4_free_inode: bit already cleared for inode 168449
EXT4-fs warning (device sdb1): ext4_unlink: Deleting nonexistent file ...
EXT4-fs warning (device sdb1): ext4_rmdir: empty directory has too many links ...
# ls -al /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71
ls: /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71: Stale NFS file handle

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: "Theodore Ts'o" 
Cc: stable@kernel.org

ext4: code cleanup

2009-01-04T03:33:39+00:00

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 
Signed-off-by: "Theodore Ts'o"

ext4: Use high 16 bits of the block group descriptor's free counts fields

2009-01-06T03:20:24+00:00

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 
Signed-off-by: "Theodore Ts'o"

ext4: Make ext4_group_t be an unsigned int

2009-01-06T03:18:16+00:00

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"

ext4: remove extraneous newlines from calls to ext4_error() and ext4_warning()

2009-01-06T03:17:35+00:00

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 
Signed-off-by: "Theodore Ts'o"

ext4: Allow ext4 to run without a journal

2009-01-07T05:06:22+00:00

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 
Signed-off-by: "Theodore Ts'o"