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    SubjectRe: 2.6.27-rc5-mm1: rmmod ide-cd_mod: tried to init an initialized object, something is seriously wrong.
    Date
    Hi,

    > > > > > > > > > Again 100% reproducible rmmod ide-cd_mod problem. Kernel is tainted because
    > > > > > > > > > of earlier sysfs acpi problems similar (probably identical) to those reported
    > > > > > > > > > by Li Zefan here http://marc.info/?l=linux-kernel&m=121921059026064&w=2
    > > > > > > > > >
    > > > > > > > > > Steps to reproduce: unload ide-cd_mod
    > > > > > > > > >
    > > > > > > > > > kobject (dd9e4a7c): tried to init an initialized object, something is seriously wrong.
    > > > > > > > > > Pid: 4734, comm: modprobe Tainted: G W 2.6.27-rc5-mm1 #1
    > > > > > > > > > [<c01ec982>] kobject_init+0xc4/0xc9
    > > > > > > > > > [<c02cb84a>] ? _spin_unlock+0x27/0x3f
    > > > > > > > > > [<c01aff2e>] ? sysfs_find_dirent+0x21/0x2b
    > > > > > > > > > [<c01aff7e>] ? __sysfs_add_one+0x46/0x6d
    > > > > > > > > > [<c01affb4>] ? sysfs_add_one+0xf/0x44
    > > > > > > > > > [<c01b0036>] ? sysfs_addrm_start+0x4d/0x90
    > > > > > > > > > [<c01b0f31>] ? sysfs_do_create_link+0x9a/0x14c
    > > > > > > > > > [<c01ec9c5>] kobject_init_and_add+0x14/0x30
    > > > > > > > > > [<c01b1009>] ? sysfs_create_link+0x12/0x19
    > > > > > > > > > [<c01e8bad>] blk_register_filter+0x3b/0x46
    > > > > > > > > > [<ded9e40a>] ide_cd_probe+0x253/0x5a8 [ide_cd_mod]
    > > > > > > > > > [<c01b0000>] ? sysfs_addrm_start+0x17/0x90
    > > > > > > > > > [<c01b0f31>] ? sysfs_do_create_link+0x9a/0x14c
    > > > > > > > > > [<c01b004e>] ? sysfs_addrm_start+0x65/0x90
    > > > > > > > > > [<c025145f>] generic_ide_probe+0x1f/0x21
    > > > > > > > > > [<c024c002>] driver_probe_device+0x77/0x15b
    > > > > > > > > > [<c02cb91b>] ? _spin_unlock_irqrestore+0x39/0x60
    > > > > > > > > > [<c024c146>] __driver_attach+0x60/0x62
    > > > > > > > > > [<c024b7bd>] bus_for_each_dev+0x44/0x62
    > > > > > > > > > [<c0251461>] ? generic_ide_remove+0x0/0x1e
    > > > > > > > > > [<c024bead>] driver_attach+0x19/0x1b
    > > > > > > > > > [<c024c0e6>] ? __driver_attach+0x0/0x62
    > > > > > > > > > [<c024bca8>] bus_add_driver+0x1ab/0x213
    > > > > > > > > > [<c0251461>] ? generic_ide_remove+0x0/0x1e
    > > > > > > > > > [<c024c291>] driver_register+0x4f/0x118
    > > > > > > > > > [<de7bf000>] ? ide_cdrom_init+0x0/0xf [ide_cd_mod]
    > > > > > > > > > [<de7bf00d>] ide_cdrom_init+0xd/0xf [ide_cd_mod]
    > > > > > > > > > [<c0101114>] do_one_initcall+0x24/0x12f
    > > > > > > > > > [<c02c9d8e>] ? mutex_unlock+0x8/0xa
    > > > > > > > > > [<c01455ca>] sys_init_module+0xa5/0x1c1
    > > > > > > > > > [<c0176a0a>] ? sys_read+0x3d/0x64
    > > > > > > > > > [<c01030f1>] sysenter_do_call+0x12/0x35
    > > > > > > > > > [<c012007b>] ? __set_special_pids+0x43/0x71
    > > > > > > > > >
    > > > > > > > > > First time I modprobe/rmmod ide-cd_mod the system works but quickly gets unstable.
    > > > > > > > > > Second modprobe/rmmod is 100% fatal. Memory gets corruped seriously I guess.
    > > > > > > > > > pcspeaker beeps all the time, kernel throws dumps on the screen until
    > > > > > > > > > its really dead, sadly blinking 'leds of panic' ;)
    > > > > > > > >
    > > > > > > > > Can you please verify if that happens with the current mainline?
    > > > > > > >
    > > > > > > > Oops. How come I didn't find it earlier? hmm...
    > > > > > >
    > > > > > > It's relatively new, that's why :) And this is the culprit:
    > > > > > >
    > > > > > > abf5439370491dd6fbb4fe1a7939680d2a9bc9d4 is first bad commit
    > > > > > > commit abf5439370491dd6fbb4fe1a7939680d2a9bc9d4
    > > > > > > Author: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    > > > > > > Date: Sat Aug 16 14:10:05 2008 +0900
    > > > > > >
    > > > > > > block: move cmdfilter from gendisk to request_queue
    > > > > > >
    > > > > > > cmd_filter works only for the block layer SG_IO with SCSI block
    > > > > > > devices. It breaks scsi/sg.c, bsg, and the block layer SG_IO with SCSI
    > > > > > > character devices (such as st). We hit a kernel crash with them.
    > > > > > >
    > > > > > > The problem is that cmd_filter code accesses to gendisk (having struct
    > > > > > > blk_scsi_cmd_filter) via inode->i_bdev->bd_disk. It works for only
    > > > > > > SCSI block device files. With character device files, inode->i_bdev
    > > > > > > leads you to struct cdev. inode->i_bdev->bd_disk->blk_scsi_cmd_filter
    > > > > > > isn't safe.
    > > > > > >
    > > > > > > SCSI ULDs don't expose gendisk; they keep it private. bsg needs to be
    > > > > > > independent on any protocols. We shouldn't change ULDs to expose their
    > > > > > > gendisk.
    > > > > > >
    > > > > > > This patch moves struct blk_scsi_cmd_filter from gendisk to
    > > > > > > request_queue, a common object, which eveyone can access to.
    > > > > > >
    > > > > > > The user interface doesn't change; users can change the filters via
    > > > > > > /sys/block/. gendisk has a pointer to request_queue so the cmd_filter
    > > > > > > code accesses to struct blk_scsi_cmd_filter.
    > > > > > >
    > > > > > > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    > > > > > > Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
    > > > > > >
    > > > > > > > This is current mainline:
    > > > > > > >
    > > > > > > > kobject (ddb049fc): tried to init an initialized object, something is seriously wrong.
    > > > > > > > Pid: 4650, comm: modprobe Not tainted 2.6.27-rc5-00132-gb380b0d #8
    > > > > > > > [<c01e3196>] kobject_init+0x6a/0x6c
    > > > > > > > [<c01e35cb>] kobject_init_and_add+0x14/0x30
    > > > > > > > [<c01e32f7>] ? kobject_get+0x12/0x17
    > > > > > > > [<c01df89c>] blk_register_filter+0x4b/0x5a
    > > > > > > > [<de839310>] ide_cd_probe+0x289/0x5ae [ide_cd_mod]
    > > > > > > > [<c01aad99>] ? sysfs_addrm_start+0x65/0x90
    > > > > > > > [<c01aba69>] ? sysfs_do_create_link+0x9a/0x11c
    > > > > > > > [<c024f7a0>] generic_ide_probe+0x1f/0x21
    > > > > > > > [<c024a672>] driver_probe_device+0x77/0x15b
    > > > > > > > [<c02c8bdb>] ? _spin_unlock_irqrestore+0x39/0x60
    > > > > > > > [<c024a7b6>] __driver_attach+0x60/0x62
    > > > > > > > [<c0249e2a>] bus_for_each_dev+0x44/0x62
    > > > > > > > [<c024f7a2>] ? generic_ide_remove+0x0/0x1e
    > > > > > > > [<c024a51d>] driver_attach+0x19/0x1b
    > > > > > > > [<c024a756>] ? __driver_attach+0x0/0x62
    > > > > > > > [<c024a318>] bus_add_driver+0x1ae/0x216
    > > > > > > > [<c024f7a2>] ? generic_ide_remove+0x0/0x1e
    > > > > > > > [<c024a901>] driver_register+0x4f/0x118
    > > > > > > > [<dee3500d>] ide_cdrom_init+0xd/0xf [ide_cd_mod]
    > > > > > > > [<c010111a>] do_one_initcall+0x2a/0x14c
    > > > > > > > [<c0108560>] ? native_sched_clock+0x58/0xa1
    > > > > > > > [<dee35000>] ? ide_cdrom_init+0x0/0xf [ide_cd_mod]
    > > > > > > > [<c013d042>] ? trace_hardirqs_on+0xb/0xd
    > > > > > > > [<c013cfaf>] ? trace_hardirqs_on_caller+0xac/0x134
    > > > > > > > [<c0147083>] sys_init_module+0x7e/0x19f
    > > > > > > > [<c013cfaf>] ? trace_hardirqs_on_caller+0xac/0x134
    > > > > > > > [<c01e8144>] ? trace_hardirqs_on_thunk+0xc/0x10
    > > > > > > > [<c0103035>] sysenter_do_call+0x12/0x35
    > > > > > > > [<c012007b>] ? put_fs_struct+0x5/0x2e
    > > > > >
    > > > > > ide-cd uses multiple gendisks share one request_queue?
    > > > > >
    > > > > > Here's a patch for mainline.
    > > > >
    > > > > Hmm, I don't think that it does. There's a queue per drive in the old
    > > > > IDE driver, so there should be a 1:1 relation between queues and gendisk
    > > > > there.
    > > >
    > > > I think the problem here is due to the usage of kobject_init_and_add().
    > > > When we hit the add the second time, the ->state_initalised in the kojb
    > > > is still 1. The below should fix it.
    > > >
    > > > The ->state_initalised stuff is a disaster imho, it should be shot and
    > > > killed.
    > > >
    > > > diff --git a/block/blk-core.c b/block/blk-core.c
    > > > index 6cb3c6d..820132b 100644
    > > > --- a/block/blk-core.c
    > > > +++ b/block/blk-core.c
    > > > @@ -495,6 +495,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
    > > > INIT_LIST_HEAD(&q->timeout_list);
    > > >
    > > > kobject_init(&q->kobj, &blk_queue_ktype);
    > > > + kobject_init(&q->cmd_filter.kobj, &rcf_ktype);
    > > >
    > > > mutex_init(&q->sysfs_lock);
    > > > spin_lock_init(&q->__queue_lock);
    > > > diff --git a/block/blk.h b/block/blk.h
    > > > index eb13740..47d6b22 100644
    > > > --- a/block/blk.h
    > > > +++ b/block/blk.h
    > > > @@ -9,6 +9,7 @@
    > > >
    > > > extern struct kmem_cache *blk_requestq_cachep;
    > > > extern struct kobj_type blk_queue_ktype;
    > > > +extern struct kobj_type rcf_ktype;
    > > >
    > > > void init_request_from_bio(struct request *req, struct bio *bio);
    > > > void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
    > > > diff --git a/block/cmd-filter.c b/block/cmd-filter.c
    > > > index da7f7a4..9556e85 100644
    > > > --- a/block/cmd-filter.c
    > > > +++ b/block/cmd-filter.c
    > > > @@ -201,7 +201,7 @@ static struct sysfs_ops rcf_sysfs_ops = {
    > > > .store = rcf_attr_store,
    > > > };
    > > >
    > > > -static struct kobj_type rcf_ktype = {
    > > > +struct kobj_type rcf_ktype = {
    > > > .sysfs_ops = &rcf_sysfs_ops,
    > > > .default_attrs = default_attrs,
    > > > };
    > > > @@ -211,8 +211,7 @@ int blk_register_filter(struct gendisk *disk)
    > > > int ret;
    > > > struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
    > > >
    > > > - ret = kobject_init_and_add(&filter->kobj, &rcf_ktype,
    > > > - &disk_to_dev(disk)->kobj,
    > > > + ret = kobject_add(&filter->kobj, &disk_to_dev(disk)->kobj,
    > > > "%s", "cmd_filter");
    > > > if (ret < 0)
    > > > return ret;
    > > >
    > >
    > > I applied your fix to 2.6.27-rc5-mm1 (it doesn't apply to mainline) and the result
    > > is that when I first rmmod ide-cd_mod it's ok, but it seems that the module is not
    > > unregistered because when you rmmod ide-cd_mod again immediately you will see this:
    > >
    > > BUG: atomic counter underflow at:
    > > Pid: 4920, comm: rmmod Tainted: G W 2.6.27-rc5-mm1 #4
    > > [<c01ec579>] ? kobject_release+0x0/0x59
    > > [<c01ed300>] kref_put+0x4c/0x7c
    > > [<c01ec4cc>] kobject_put+0x20/0x4e
    > > [<c01aed10>] ? sysfs_hash_and_remove+0x50/0x57
    > > [<c01e8d4b>] blk_unregister_filter+0x13/0x15
    > > [<dedd822b>] ide_cd_remove+0xf/0x21 [ide_cd_mod]
    > > [<c025147b>] generic_ide_remove+0x1a/0x1e
    > > [<c024bdaf>] __device_release_driver+0x59/0x7f
    > > [<c024be6c>] driver_detach+0x97/0x99
    > > [<c024b26e>] bus_remove_driver+0x6f/0x8b
    > > [<c024c231>] driver_unregister+0x2f/0x33
    > > [<deddb341>] ide_cdrom_exit+0xd/0xf [ide_cd_mod]
    > > [<c0143da5>] sys_delete_module+0x10d/0x1e2
    > > [<c0162cbc>] ? do_munmap+0x1d7/0x234
    > > [<c0163d13>] ? sys_munmap+0x30/0x36
    > > [<c01030f1>] sysenter_do_call+0x12/0x35
    > > =======================
    > > hdc: ATAPI 24X DVD-ROM CD-R/RW drive, 2048kB Cache
    > >
    > > Btw I found something interesting. On earlier kernels - 2.6.25 I can not remove ide-cd_mod
    > > at all - it's still there when I lsmod modules:
    > >
    > > # modprobe ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # rmmod ide-cd_mod
    > > # lsmod | grep ide_cd
    > > ide_cd_mod 29600 0
    > > cdrom 32160 1 ide_cd_mod
    > >
    > > On the other hand on newer kernels (post 2.6.26 - these which did not blow up) right
    > > after boot I have to run rmmod ide-cd_mod exactly three times to have ide-cd_mod
    > > unloaded. If I modprobe and rmmod again it works as expected. Why is this?
    > >
    > > laptop mako # modprobe ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > ERROR: Module ide_cd_mod does not exist in /proc/modules
    > > laptop mako # modprobe ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > laptop mako # rmmod ide-cd_mod
    > > ERROR: Module ide_cd_mod does not exist in /proc/modules
    >
    > Can you try the below patch from Elias?

    Sure. It applied fine to clean current mainline. It looks ok now. No oopses and no BUGs.
    But still after a fresh boot I see

    # modprobe ide-cd_mod
    # rmmod ide-cd_mod
    # rmmod ide-cd_mod
    # rmmod ide-cd_mod
    ERROR: Module ide_cd_mod does not exist in /proc/modules
    # modprobe ide-cd_mod
    # rmmod ide-cd_mod
    # rmmod ide-cd_mod
    ERROR: Module ide_cd_mod does not exist in /proc/modules

    You need to rmmod ide-cd_mod twice to get it unloaded. After another
    modprobe/rmmod it works as expected.

    Mariusz

    Tested-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>

    > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
    > index 304ec73..0120c8e 100644
    > --- a/block/blk-sysfs.c
    > +++ b/block/blk-sysfs.c
    > @@ -9,12 +9,6 @@
    >
    > #include "blk.h"
    >
    > -struct queue_sysfs_entry {
    > - struct attribute attr;
    > - ssize_t (*show)(struct request_queue *, char *);
    > - ssize_t (*store)(struct request_queue *, const char *, size_t);
    > -};
    > -
    > static ssize_t
    > queue_var_show(unsigned int var, char *page)
    > {
    > diff --git a/block/blk.h b/block/blk.h
    > index c79f30e..9ab0d6a 100644
    > --- a/block/blk.h
    > +++ b/block/blk.h
    > @@ -10,6 +10,12 @@
    > extern struct kmem_cache *blk_requestq_cachep;
    > extern struct kobj_type blk_queue_ktype;
    >
    > +struct queue_sysfs_entry {
    > + struct attribute attr;
    > + ssize_t (*show)(struct request_queue *, char *);
    > + ssize_t (*store)(struct request_queue *, const char *, size_t);
    > +};
    > +
    > void init_request_from_bio(struct request *req, struct bio *bio);
    > void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
    > struct bio *bio);
    > diff --git a/block/cmd-filter.c b/block/cmd-filter.c
    > index 228b644..fc0f0b2 100644
    > --- a/block/cmd-filter.c
    > +++ b/block/cmd-filter.c
    > @@ -26,6 +26,8 @@
    > #include <scsi/scsi.h>
    > #include <linux/cdrom.h>
    >
    > +#include "blk.h"
    > +
    > int blk_verify_command(struct blk_cmd_filter *filter,
    > unsigned char *cmd, int has_write_perm)
    > {
    > @@ -50,9 +52,9 @@ int blk_verify_command(struct blk_cmd_filter *filter,
    > EXPORT_SYMBOL(blk_verify_command);
    >
    > /* and now, the sysfs stuff */
    > -static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
    > - int rw)
    > +static ssize_t rcf_cmds_show(struct request_queue *q, char *page, int rw)
    > {
    > + struct blk_cmd_filter *filter = &q->cmd_filter;
    > char *npage = page;
    > unsigned long *okbits;
    > int i;
    > @@ -76,24 +78,27 @@ static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
    > return npage - page;
    > }
    >
    > -static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
    > +static ssize_t rcf_readcmds_show(struct request_queue *q, char *page)
    > {
    > - return rcf_cmds_show(filter, page, READ);
    > + return rcf_cmds_show(q, page, READ);
    > }
    >
    > -static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
    > - char *page)
    > +static ssize_t rcf_writecmds_show(struct request_queue *q, char *page)
    > {
    > - return rcf_cmds_show(filter, page, WRITE);
    > + return rcf_cmds_show(q, page, WRITE);
    > }
    >
    > -static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
    > - const char *page, size_t count, int rw)
    > +static ssize_t rcf_cmds_store(struct request_queue *q, const char *page,
    > + size_t count, int rw)
    > {
    > + struct blk_cmd_filter *filter = &q->cmd_filter;
    > unsigned long okbits[BLK_SCSI_CMD_PER_LONG], *target_okbits;
    > int cmd, set;
    > char *p, *status;
    >
    > + if (!capable(CAP_SYS_RAWIO))
    > + return -EPERM;
    > +
    > if (rw == READ) {
    > memcpy(&okbits, filter->read_ok, sizeof(okbits));
    > target_okbits = filter->read_ok;
    > @@ -128,31 +133,25 @@ static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
    > return count;
    > }
    >
    > -static ssize_t rcf_readcmds_store(struct blk_cmd_filter *filter,
    > - const char *page, size_t count)
    > +static ssize_t rcf_readcmds_store(struct request_queue *q, const char *page,
    > + size_t count)
    > {
    > - return rcf_cmds_store(filter, page, count, READ);
    > + return rcf_cmds_store(q, page, count, READ);
    > }
    >
    > -static ssize_t rcf_writecmds_store(struct blk_cmd_filter *filter,
    > - const char *page, size_t count)
    > +static ssize_t rcf_writecmds_store(struct request_queue *q, const char *page,
    > + size_t count)
    > {
    > - return rcf_cmds_store(filter, page, count, WRITE);
    > + return rcf_cmds_store(q, page, count, WRITE);
    > }
    >
    > -struct rcf_sysfs_entry {
    > - struct attribute attr;
    > - ssize_t (*show)(struct blk_cmd_filter *, char *);
    > - ssize_t (*store)(struct blk_cmd_filter *, const char *, size_t);
    > -};
    > -
    > -static struct rcf_sysfs_entry rcf_readcmds_entry = {
    > +static struct queue_sysfs_entry rcf_readcmds_entry = {
    > .attr = { .name = "read_table", .mode = S_IRUGO | S_IWUSR },
    > .show = rcf_readcmds_show,
    > .store = rcf_readcmds_store,
    > };
    >
    > -static struct rcf_sysfs_entry rcf_writecmds_entry = {
    > +static struct queue_sysfs_entry rcf_writecmds_entry = {
    > .attr = {.name = "write_table", .mode = S_IRUGO | S_IWUSR },
    > .show = rcf_writecmds_show,
    > .store = rcf_writecmds_store,
    > @@ -164,72 +163,30 @@ static struct attribute *default_attrs[] = {
    > NULL,
    > };
    >
    > -#define to_rcf(atr) container_of((atr), struct rcf_sysfs_entry, attr)
    > -
    > -static ssize_t
    > -rcf_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
    > -{
    > - struct rcf_sysfs_entry *entry = to_rcf(attr);
    > - struct blk_cmd_filter *filter;
    > -
    > - filter = container_of(kobj, struct blk_cmd_filter, kobj);
    > - if (entry->show)
    > - return entry->show(filter, page);
    > -
    > - return 0;
    > -}
    > -
    > -static ssize_t
    > -rcf_attr_store(struct kobject *kobj, struct attribute *attr,
    > - const char *page, size_t length)
    > -{
    > - struct rcf_sysfs_entry *entry = to_rcf(attr);
    > - struct blk_cmd_filter *filter;
    > -
    > - if (!capable(CAP_SYS_RAWIO))
    > - return -EPERM;
    > -
    > - if (!entry->store)
    > - return -EINVAL;
    > -
    > - filter = container_of(kobj, struct blk_cmd_filter, kobj);
    > - return entry->store(filter, page, length);
    > -}
    > -
    > -static struct sysfs_ops rcf_sysfs_ops = {
    > - .show = rcf_attr_show,
    > - .store = rcf_attr_store,
    > -};
    > -
    > -static struct kobj_type rcf_ktype = {
    > - .sysfs_ops = &rcf_sysfs_ops,
    > - .default_attrs = default_attrs,
    > +static struct attribute_group rcf_attr_group = {
    > + .name = "cmd_filter",
    > + .attrs = default_attrs,
    > };
    >
    > int blk_register_filter(struct gendisk *disk)
    > {
    > + struct kobject *kobj = &disk->queue->kobj;
    > int ret;
    > - struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
    > - struct kobject *parent = kobject_get(disk->holder_dir->parent);
    >
    > - if (!parent)
    > - return -ENODEV;
    > + ret = sysfs_create_group(kobj, &rcf_attr_group);
    > + if (!ret)
    > + ret = sysfs_create_link_to_group(disk->holder_dir->parent,
    > + kobj, rcf_attr_group.name,
    > + rcf_attr_group.name);
    > + WARN_ON(ret);
    >
    > - ret = kobject_init_and_add(&filter->kobj, &rcf_ktype, parent,
    > - "%s", "cmd_filter");
    > -
    > - if (ret < 0)
    > - return ret;
    > -
    > - return 0;
    > + return ret;
    > }
    > EXPORT_SYMBOL(blk_register_filter);
    >
    > void blk_unregister_filter(struct gendisk *disk)
    > {
    > - struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
    > -
    > - kobject_put(&filter->kobj);
    > - kobject_put(disk->holder_dir->parent);
    > + sysfs_remove_link(disk->holder_dir->parent, rcf_attr_group.name);
    > + sysfs_remove_group(&disk->queue->kobj, &rcf_attr_group);
    > }
    > EXPORT_SYMBOL(blk_unregister_filter);
    > diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
    > index a3ba217..d2813a1 100644
    > --- a/fs/sysfs/symlink.c
    > +++ b/fs/sysfs/symlink.c
    > @@ -19,22 +19,16 @@
    >
    > #include "sysfs.h"
    >
    > -static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
    > +static int sysfs_sd_create_link(struct sysfs_dirent *parent_sd,
    > + struct sysfs_dirent *target_sd,
    > const char *name, int warn)
    > {
    > - struct sysfs_dirent *parent_sd = NULL;
    > - struct sysfs_dirent *target_sd = NULL;
    > struct sysfs_dirent *sd = NULL;
    > struct sysfs_addrm_cxt acxt;
    > int error;
    >
    > BUG_ON(!name);
    >
    > - if (!kobj)
    > - parent_sd = &sysfs_root;
    > - else
    > - parent_sd = kobj->sd;
    > -
    > error = -EFAULT;
    > if (!parent_sd)
    > goto out_put;
    > @@ -43,8 +37,8 @@ static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
    > * sysfs_assoc_lock. Fetch target_sd from it.
    > */
    > spin_lock(&sysfs_assoc_lock);
    > - if (target->sd)
    > - target_sd = sysfs_get(target->sd);
    > + if (target_sd)
    > + target_sd = sysfs_get(target_sd);
    > spin_unlock(&sysfs_assoc_lock);
    >
    > error = -ENOENT;
    > @@ -77,6 +71,19 @@ static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
    > return error;
    > }
    >
    > +static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
    > + const char *name, int warn)
    > +{
    > + struct sysfs_dirent *parent_sd;
    > +
    > + if (!kobj)
    > + parent_sd = &sysfs_root;
    > + else
    > + parent_sd = kobj->sd;
    > +
    > + return sysfs_sd_create_link(parent_sd, target->sd, name, warn);
    > +}
    > +
    > /**
    > * sysfs_create_link - create symlink between two objects.
    > * @kobj: object whose directory we're creating the link in.
    > @@ -104,6 +111,26 @@ int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
    > return sysfs_do_create_link(kobj, target, name, 0);
    > }
    >
    > +int sysfs_create_link_to_group(struct kobject *kobj, struct kobject *target,
    > + const char *group, const char *linkname)
    > +{
    > + struct sysfs_dirent *sd;
    > + int ret;
    > +
    > + BUG_ON(!kobj || !target);
    > +
    > + sd = sysfs_get_dirent(target->sd, group);
    > + if (!sd) {
    > + WARN(!sd, KERN_WARNING "sysfs group %p not found for "
    > + "kobject '%s'\n", group, kobject_name(target));
    > + return -ENOENT;
    > + }
    > +
    > + ret = sysfs_sd_create_link(kobj->sd, sd, linkname, 1);
    > + sysfs_put(sd);
    > + return ret;
    > +}
    > +
    > /**
    > * sysfs_remove_link - remove symlink in object's directory.
    > * @kobj: object we're acting for.
    > @@ -213,4 +240,5 @@ const struct inode_operations sysfs_symlink_inode_operations = {
    >
    >
    > EXPORT_SYMBOL_GPL(sysfs_create_link);
    > +EXPORT_SYMBOL_GPL(sysfs_create_link_to_group);
    > EXPORT_SYMBOL_GPL(sysfs_remove_link);
    > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    > index 44710d7..ca616b7 100644
    > --- a/include/linux/blkdev.h
    > +++ b/include/linux/blkdev.h
    > @@ -286,7 +286,6 @@ struct blk_queue_tag {
    > struct blk_cmd_filter {
    > unsigned long read_ok[BLK_SCSI_CMD_PER_LONG];
    > unsigned long write_ok[BLK_SCSI_CMD_PER_LONG];
    > - struct kobject kobj;
    > };
    >
    > struct request_queue
    > diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
    > index 37fa241..e9e0971 100644
    > --- a/include/linux/sysfs.h
    > +++ b/include/linux/sysfs.h
    > @@ -116,6 +116,8 @@ int sysfs_add_file_to_group(struct kobject *kobj,
    > const struct attribute *attr, const char *group);
    > void sysfs_remove_file_from_group(struct kobject *kobj,
    > const struct attribute *attr, const char *group);
    > +int sysfs_create_link_to_group(struct kobject *kobj, struct kobject *target,
    > + const char *grpname, const char *linkname);
    >
    > void sysfs_notify(struct kobject *kobj, char *dir, char *attr);
    >
    >




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