The patch titled
Subject: zram: check bd_openers instead of bd_holders
has been added to the -mm tree. Its filename is
zram-check-bd_openers-instead-bd_holders.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-check-bd_openers-instead-bd_holders.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-check-bd_openers-instead-bd_holders.patch
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------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: zram: check bd_openers instead of bd_holders
bd_holders is increased only when user open the device file as FMODE_EXCL
so if something opens zram0 as !FMODE_EXCL and request I/O while another
user reset zram0, we can see following warning.
[ 30.683449] zram0: detected capacity change from 0 to 64424509440
[ 33.736869] Buffer I/O error on dev zram0, logical block 180823, lost async page write
[ 33.738814] Buffer I/O error on dev zram0, logical block 180824, lost async page write
[ 33.740654] Buffer I/O error on dev zram0, logical block 180825, lost async page write
[ 33.742551] Buffer I/O error on dev zram0, logical block 180826, lost async page write
[ 33.744153] Buffer I/O error on dev zram0, logical block 180827, lost async page write
[ 33.745807] Buffer I/O error on dev zram0, logical block 180828, lost async page write
[ 33.747419] Buffer I/O error on dev zram0, logical block 180829, lost async page write
[ 33.749060] Buffer I/O error on dev zram0, logical block 180830, lost async page write
[ 33.750687] Buffer I/O error on dev zram0, logical block 180831, lost async page write
[ 33.752286] Buffer I/O error on dev zram0, logical block 180832, lost async page write
[ 33.811590] ------------[ cut here ]------------
[ 33.812038] WARNING: CPU: 11 PID: 1996 at fs/block_dev.c:57 __blkdev_put+0x1d7/0x210()
[ 33.812817] Modules linked in:
[ 33.813142] CPU: 11 PID: 1996 Comm: dd Not tainted 3.19.0-rc6-next-20150202+ #1125
[ 33.813837] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[ 33.814525] ffffffff81801a2d ffff880061e77db8 ffffffff815b848e 0000000000000001
[ 33.815196] 0000000000000000 ffff880061e77df8 ffffffff8104de2a 0000000000000000
[ 33.815867] ffff88005da287f0 ffff88005da28680 ffff88005da28770 ffff88005da28698
[ 33.816536] Call Trace:
[ 33.816817] [<ffffffff815b848e>] dump_stack+0x45/0x57
[ 33.817304] [<ffffffff8104de2a>] warn_slowpath_common+0x8a/0xc0
[ 33.817829] [<ffffffff8104df1a>] warn_slowpath_null+0x1a/0x20
[ 33.818331] [<ffffffff811b60b7>] __blkdev_put+0x1d7/0x210
[ 33.818797] [<ffffffff811b69c0>] blkdev_put+0x50/0x130
[ 33.819244] [<ffffffff811b6b55>] blkdev_close+0x25/0x30
[ 33.819723] [<ffffffff8118079f>] __fput+0xdf/0x1e0
[ 33.820140] [<ffffffff811808ee>] ____fput+0xe/0x10
[ 33.820576] [<ffffffff81068e07>] task_work_run+0xa7/0xe0
[ 33.821151] [<ffffffff81002b89>] do_notify_resume+0x49/0x60
[ 33.821721] [<ffffffff815bf09d>] int_signal+0x12/0x17
[ 33.822228] ---[ end trace 274fbbc5664827d2 ]---
The warning comes from bdev_write_node in blkdev_put path.
tatic void bdev_write_inode(struct inode *inode)
{
spin_lock(&inode->i_lock);
while (inode->i_state & I_DIRTY) {
spin_unlock(&inode->i_lock);
WARN_ON_ONCE(write_inode_now(inode, true)); <========= here.
spin_lock(&inode->i_lock);
}
spin_unlock(&inode->i_lock);
}
The reason is dd process encounters I/O fails due to sudden block device
disappear so in filemap_check_errors in __writeback_single_inode returns
-EIO.
If we check bd_openers instead of bd_holders, we could address the
problem. When I see the brd, it already have used it rather than
bd_holders so although I'm not a expert of block layer, it seems to be
better.
I can make following warning with below simple script. In addition, I
added msleep(2000) below set_capacity(zram->disk, 0) after applying your
patch to make window huge(Kudos to Ganesh!)
script:
echo $((60<<30)) > /sys/block/zram0/disksize
setsid dd if=/dev/zero of=/dev/zram0 &
sleep 1
setsid echo 1 > /sys/block/zram0/reset
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN drivers/block/zram/zram_drv.c~zram-check-bd_openers-instead-bd_holders drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-check-bd_openers-instead-bd_holders
+++ a/drivers/block/zram/zram_drv.c
@@ -810,7 +810,7 @@ static ssize_t reset_store(struct device
mutex_lock(&bdev->bd_mutex);
/* Do not reset an active device! */
- if (bdev->bd_holders) {
+ if (bdev->bd_openers) {
ret = -EBUSY;
goto out;
}
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
mm-set-page-pfmemalloc-in-prep_new_page.patch
mm-page_alloc-reduce-number-of-alloc_pages-functions-parameters.patch
mm-reduce-try_to_compact_pages-parameters.patch
mm-microoptimize-zonelist-operations.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated-fix.patch
mm-when-stealing-freepages-also-take-pages-created-by-splitting-buddy-page.patch
mm-always-steal-split-buddies-in-fallback-allocations.patch
mm-more-aggressive-page-stealing-for-unmovable-allocations.patch
vmstat-do-not-use-deferrable-delayed-work-for-vmstat_update.patch
mm-page_isolation-check-pfn-validity-before-access.patch
mm-support-madvisemadv_free.patch
mm-support-madvisemadv_free-fix.patch
x86-add-pmd_-for-thp.patch
x86-add-pmd_-for-thp-fix.patch
sparc-add-pmd_-for-thp.patch
sparc-add-pmd_-for-thp-fix.patch
powerpc-add-pmd_-for-thp.patch
arm-add-pmd_mkclean-for-thp.patch
arm64-add-pmd_-for-thp.patch
mm-dont-split-thp-page-when-syscall-is-called.patch
mm-dont-split-thp-page-when-syscall-is-called-fix.patch
mm-dont-split-thp-page-when-syscall-is-called-fix-2.patch
zram-clean-up-zram_meta_alloc.patch
zram-free-meta-table-in-zram_meta_free.patch
zram-fix-umount-reset_store-mount-race-condition.patch
zram-rework-reset-and-destroy-path.patch
zram-rework-reset-and-destroy-path-fix.patch
zram-check-bd_openers-instead-bd_holders.patch
mm-zpool-add-name-argument-to-create-zpool.patch
mm-zsmalloc-add-statistics-support.patch
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