[ 3.5.y.z extended stable ] Patch "block: fix ext_devt_idr handling" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    block: fix ext_devt_idr handling

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5ee3fa6d9e4d5bdde191e3651257f13383e1a99b Mon Sep 17 00:00:00 2001
From: Tomas Henzl <thenzl at redhat.com>
Date: Wed, 27 Feb 2013 17:03:32 -0800
Subject: [PATCH] block: fix ext_devt_idr handling

commit 7b74e912785a11572da43292786ed07ada7e3e0c upstream.

While adding and removing a lot of disks disks and partitions this
sometimes shows up:

  WARNING: at fs/sysfs/dir.c:512 sysfs_add_one+0xc9/0x130() (Not tainted)
  Hardware name:
  sysfs: cannot create duplicate filename '/dev/block/259:751'
  Modules linked in: raid1 autofs4 bnx2fc cnic uio fcoe libfcoe libfc 8021q scsi_transport_fc scsi_tgt garp stp llc sunrpc cpufreq_ondemand powernow_k8 freq_table mperf ipv6 dm_mirror dm_region_hash dm_log power_meter microcode dcdbas serio_raw amd64_edac_mod edac_core edac_mce_amd i2c_piix4 i2c_core k10temp bnx2 sg ixgbe dca mdio ext4 mbcache jbd2 dm_round_robin sr_mod cdrom sd_mod crc_t10dif ata_generic pata_acpi pata_atiixp ahci mptsas mptscsih mptbase scsi_transport_sas dm_multipath dm_mod [last unloaded: scsi_wait_scan]
  Pid: 44103, comm: async/16 Not tainted 2.6.32-195.el6.x86_64 #1
  Call Trace:
    warn_slowpath_common+0x87/0xc0
    warn_slowpath_fmt+0x46/0x50
    sysfs_add_one+0xc9/0x130
    sysfs_do_create_link+0x12b/0x170
    sysfs_create_link+0x13/0x20
    device_add+0x317/0x650
    idr_get_new+0x13/0x50
    add_partition+0x21c/0x390
    rescan_partitions+0x32b/0x470
    sd_open+0x81/0x1f0 [sd_mod]
    __blkdev_get+0x1b6/0x3c0
    blkdev_get+0x10/0x20
    register_disk+0x155/0x170
    add_disk+0xa6/0x160
    sd_probe_async+0x13b/0x210 [sd_mod]
    add_wait_queue+0x46/0x60
    async_thread+0x102/0x250
    default_wake_function+0x0/0x20
    async_thread+0x0/0x250
    kthread+0x96/0xa0
    child_rip+0xa/0x20
    kthread+0x0/0xa0
    child_rip+0x0/0x20

This most likely happens because dev_t is freed while the number is
still used and idr_get_new() is not protected on every use.  The fix
adds a mutex where it wasn't before and moves the dev_t free function so
it is called after device del.

Signed-off-by: Tomas Henzl <thenzl at redhat.com>
Cc: Jens Axboe <axboe at kernel.dk>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ luis: adjust context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 block/genhd.c             | 6 +++++-
 block/partition-generic.c | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 9cf5583..9433636 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -420,14 +420,18 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
 	do {
 		if (!idr_pre_get(&ext_devt_idr, GFP_KERNEL))
 			return -ENOMEM;
+		mutex_lock(&ext_devt_mutex);
 		rc = idr_get_new(&ext_devt_idr, part, &idx);
+		mutex_unlock(&ext_devt_mutex);
 	} while (rc == -EAGAIN);

 	if (rc)
 		return rc;

 	if (idx > MAX_EXT_DEVT) {
+		mutex_lock(&ext_devt_mutex);
 		idr_remove(&ext_devt_idr, idx);
+		mutex_unlock(&ext_devt_mutex);
 		return -EBUSY;
 	}

@@ -644,7 +648,6 @@ void del_gendisk(struct gendisk *disk)
 	disk_part_iter_exit(&piter);

 	invalidate_partition(disk, 0);
-	blk_free_devt(disk_to_dev(disk)->devt);
 	set_capacity(disk, 0);
 	disk->flags &= ~GENHD_FL_UP;

@@ -662,6 +665,7 @@ void del_gendisk(struct gendisk *disk)
 	if (!sysfs_deprecated)
 		sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
 	device_del(disk_to_dev(disk));
+	blk_free_devt(disk_to_dev(disk)->devt);
 }
 EXPORT_SYMBOL(del_gendisk);

diff --git a/block/partition-generic.c b/block/partition-generic.c
index 6df5d69..7b8b8d1 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -249,11 +249,11 @@ void delete_partition(struct gendisk *disk, int partno)
 	if (!part)
 		return;

-	blk_free_devt(part_devt(part));
 	rcu_assign_pointer(ptbl->part[partno], NULL);
 	rcu_assign_pointer(ptbl->last_lookup, NULL);
 	kobject_put(part->holder_dir);
 	device_del(part_to_dev(part));
+	blk_free_devt(part_devt(part));

 	hd_struct_put(part);
 }
--
1.8.1.2