linux-stable.git/drivers/block/zram, branch v3.16

zram: avoid lockdep splat by revalidate_disk

2014-07-23T22:10:54+00:00

Sasha reported lockdep warning [1] introduced by [2].

It could be fixed by doing disk revalidation out of the init_lock.  It's
okay because disk capacity change is protected by init_lock so that
revalidate_disk always sees up-to-date value so there is no race.

[1] https://lkml.org/lkml/2014/7/3/735
[2] zram: revalidate disk after capacity change

Fixes 2e32baea46ce ("zram: revalidate disk after capacity change").

Signed-off-by: Minchan Kim 
Reported-by: Sasha Levin 
Cc: "Alexander E. Patrakov" 
Cc: Nitin Gupta 
Cc: Jerome Marchand 
Cc: Sergey Senozhatsky 
CC: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: revalidate disk after capacity change

2014-07-03T16:21:53+00:00

Alexander reported mkswap on /dev/zram0 is failed if other process is
opening the block device file.

Step is as follows,

0. Reset the unused zram device.
1. Use a program that opens /dev/zram0 with O_RDWR and sleeps
   until killed.
2. While that program sleeps, echo the correct value to
   /sys/block/zram0/disksize.
3. Verify (e.g. in /proc/partitions) that the disk size is applied
   correctly. It is.
4. While that program still sleeps, attempt to mkswap /dev/zram0.
   This fails: mkswap: error: swap area needs to be at least 40 KiB

When I investigated, the size get by ioctl(fd, BLKGETSIZE64, xxx) on
mkswap to get a size of blockdev was zero although zram0 has right size by
2.

The reason is zram didn't revalidate disk after changing capacity so that
size of blockdev's inode is not uptodate until all of file is close.

This patch should fix the BUG.

Signed-off-by: Minchan Kim 
Reported-by: Alexander E. Patrakov 
Tested-by: Alexander E. Patrakov 
Reviewed-by: Sergey Senozhatsky 
Cc: Nitin Gupta 
Acked-by: Jerome Marchand 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: correct offset usage in zram_bio_discard

2014-06-04T23:54:13+00:00

We want to skip the physical block(PAGE_SIZE) which is partially covered
by the discard bio, so we check the remaining size and subtract it if
there is a need to goto the next physical block.

The current offset usage in zram_bio_discard is incorrect, it will cause
its upper filesystem breakdown.  Consider the following scenario:

On some architecture or config, PAGE_SIZE is 64K for example, filesystem
is set up on zram disk without PAGE_SIZE aligned, a discard bio leads to a
offset = 4K and size=72K, normally, it should not really discard any
physical block as it partially cover two physical blocks.  However, with
the current offset usage, it will discard the second physical block and
free its memory, which will cause filesystem breakdown.

This patch corrects the offset usage in zram_bio_discard.

Signed-off-by: Weijie Yang 
Cc: Minchan Kim 
Cc: Nitin Gupta 
Acked-by: Joonsoo Kim 
Cc: Sergey Senozhatsky 
Cc: Bob Liu 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: support REQ_DISCARD

2014-04-07T23:36:02+00:00

zram is ram based block device and can be used by backend of filesystem.
When filesystem deletes a file, it normally doesn't do anything on data
block of that file.  It just marks on metadata of that file.  This
behavior has no problem on disk based block device, but has problems on
ram based block device, since we can't free memory used for data block.
To overcome this disadvantage, there is REQ_DISCARD functionality.  If
block device support REQ_DISCARD and filesystem is mounted with discard
option, filesystem sends REQ_DISCARD to block device whenever some data
blocks are discarded.  All we have to do is to handle this request.

This patch implements to flag up QUEUE_FLAG_DISCARD and handle this
REQ_DISCARD request.  With it, we can free memory used by zram if it isn't
used.

[akpm@linux-foundation.org: tweak comments]
Signed-off-by: Joonsoo Kim 
Cc: Minchan Kim 
Cc: Nitin Gupta 
Cc: Sergey Senozhatsky 
Cc: Jerome Marchand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: use scnprintf() in attrs show() methods

2014-04-07T23:36:02+00:00

sysfs.txt documentation lists the following requirements:

 - The buffer will always be PAGE_SIZE bytes in length. On i386, this
   is 4096.

 - show() methods should return the number of bytes printed into the
   buffer. This is the return value of scnprintf().

 - show() should always use scnprintf().

Use scnprintf() in show() functions.

Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Jerome Marchand 
Cc: Nitin Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: propagate error to user

2014-04-07T23:36:02+00:00

When we initialized zcomp with single, we couldn't change
max_comp_streams without zram reset but current interface doesn't show
any error to user and even it changes max_comp_streams's value without
any effect so it would make user very confusing.

This patch prevents max_comp_streams's change when zcomp was initialized
as single zcomp and emit the error to user(ex, echo).

[akpm@linux-foundation.org: don't return with the lock held, per Sergey]
[fengguang.wu@intel.com: fix coccinelle warnings]
Signed-off-by: Minchan Kim 
Cc: Nitin Gupta 
Cc: Jerome Marchand 
Acked-by: Sergey Senozhatsky 
Signed-off-by: Fengguang Wu 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: return error-valued pointer from zcomp_create()

2014-04-07T23:36:02+00:00

Instead of returning just NULL, return ERR_PTR from zcomp_create() if
compressing backend creation has failed.  ERR_PTR(-EINVAL) for unsupported
compression algorithm request, ERR_PTR(-ENOMEM) for allocation (zcomp or
compression stream) error.

Perform IS_ERR() check of returned from zcomp_create() value in
disksize_store() and set return code to PTR_ERR().

Change suggested by Jerome Marchand.

[akpm@linux-foundation.org: clean up error recovery flow]
Signed-off-by: Sergey Senozhatsky 
Reported-by: Jerome Marchand 
Cc: Minchan Kim 
Cc: Nitin Gupta 
Cc: Arnd Bergmann 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: move comp allocation out of init_lock

2014-04-07T23:36:02+00:00

While fixing lockdep spew of ->init_lock reported by Sasha Levin [1],
Minchan Kim noted [2] that it's better to move compression backend
allocation (using GPF_KERNEL) out of the ->init_lock lock, same way as
with zram_meta_alloc(), in order to prevent the same lockdep spew.

[1] https://lkml.org/lkml/2014/2/27/337
[2] https://lkml.org/lkml/2014/3/3/32

Signed-off-by: Sergey Senozhatsky 
Reported-by: Minchan Kim 
Acked-by: Minchan Kim 
Cc: Sasha Levin 
Acked-by: Jerome Marchand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: add lz4 algorithm backend

2014-04-07T23:36:01+00:00

Introduce LZ4 compression backend and make it available for selection.
LZ4 support is optional and requires user to set ZRAM_LZ4_COMPRESS config
option.  The default compression backend is LZO.

TEST

(x86_64, core i5, 2 cores + 2 hyperthreading, zram disk size 1G,
ext4 file system, 3 compression streams)

iozone -t 3 -R -r 16K -s 60M -I +Z

       Test           LZO           LZ4
----------------------------------------------
  Initial write   1642744.62    1317005.09
        Rewrite   2498980.88    1800645.16
           Read   3957026.38    5877043.75
        Re-read   3950997.38    5861847.00
   Reverse Read   2937114.56    5047384.00
    Stride read   2948163.19    4929587.38
    Random read   3292692.69    4880793.62
 Mixed workload   1545602.62    3502940.38
   Random write   2448039.75    1758786.25
         Pwrite   1670051.03    1338329.69
          Pread   2530682.00    5097177.62
         Fwrite   3232085.62    3275942.56
          Fread   6306880.25    6645271.12

So on my system LZ4 is slower in write-only tests, while it performs
better in read-only and mixed (reads + writes) tests.

Official LZ4 benchmarks available here http://code.google.com/p/lz4/
(linux kernel uses revision r90).

Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Jerome Marchand 
Cc: Nitin Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

zram: make compression algorithm selection possible

2014-04-07T23:36:01+00:00

Add and document `comp_algorithm' device attribute.  This attribute allows
to show supported compression and currently selected compression
algorithms:

	cat /sys/block/zram0/comp_algorithm
	[lzo] lz4

and change selected compression algorithm:
	echo lzo > /sys/block/zram0/comp_algorithm

Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Jerome Marchand 
Cc: Nitin Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds