* [PATCH 0/2] block: 7th -- last batch of add_disk() error handling conversions
@ 2021-09-04 1:39 Luis Chamberlain
2021-09-04 1:39 ` [PATCH 1/2] block: make __register_blkdev() return an error Luis Chamberlain
2021-09-04 1:39 ` [PATCH 2/2] block: add __must_check for *add_disk*() callers Luis Chamberlain
0 siblings, 2 replies; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-04 1:39 UTC (permalink / raw)
To: axboe, hch, efremov, song, jejb, martin.petersen, viro, hare,
jack, ming.lei, tj
Cc: linux-raid, linux-scsi, linux-fsdevel, linux-block, linux-kernel,
Luis Chamberlain
This is the 7th and final set of changes to convert all drivers over to
use and finally enforce add_disk() error handling. This set deals with
those old drivers using __register_blkdev() which in turn have a
respective add_disk() call made. The last patch ensures we won't
add new drivers without a check for the add_disk() call.
You can find the full set of patches on my kernel.org linux
20210901-for-axboe-add-disk-error-handling branch [0] which is now based
on axboe/master.
[0] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20210901-for-axboe-add-disk-error-handling
Luis Chamberlain (2):
block: make __register_blkdev() return an error
block: add __must_check for *add_disk*() callers
block/genhd.c | 21 ++++++++++++---------
drivers/block/ataflop.c | 20 +++++++++++++++-----
drivers/block/brd.c | 7 +++++--
drivers/block/floppy.c | 14 ++++++++++----
drivers/block/loop.c | 6 +++---
drivers/md/md.c | 10 +++++++---
drivers/scsi/sd.c | 3 ++-
fs/block_dev.c | 5 ++++-
include/linux/genhd.h | 10 +++++-----
9 files changed, 63 insertions(+), 33 deletions(-)
--
2.30.2
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-04 1:39 [PATCH 0/2] block: 7th -- last batch of add_disk() error handling conversions Luis Chamberlain
@ 2021-09-04 1:39 ` Luis Chamberlain
2021-09-04 2:49 ` Tetsuo Handa
2021-09-04 1:39 ` [PATCH 2/2] block: add __must_check for *add_disk*() callers Luis Chamberlain
1 sibling, 1 reply; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-04 1:39 UTC (permalink / raw)
To: axboe, hch, efremov, song, jejb, martin.petersen, viro, hare,
jack, ming.lei, tj
Cc: linux-raid, linux-scsi, linux-fsdevel, linux-block, linux-kernel,
Luis Chamberlain
This makes __register_blkdev() return an error, and
also changes the probe() call to return an error as well.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
block/genhd.c | 15 +++++++++------
drivers/block/ataflop.c | 20 +++++++++++++++-----
drivers/block/brd.c | 7 +++++--
drivers/block/floppy.c | 14 ++++++++++----
drivers/block/loop.c | 6 +++---
drivers/md/md.c | 10 +++++++---
drivers/scsi/sd.c | 3 ++-
fs/block_dev.c | 5 ++++-
include/linux/genhd.h | 4 ++--
9 files changed, 57 insertions(+), 27 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 567549a011d1..c4836296a974 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -180,7 +180,7 @@ static struct blk_major_name {
struct blk_major_name *next;
int major;
char name[16];
- void (*probe)(dev_t devt);
+ int (*probe)(dev_t devt);
} *major_names[BLKDEV_MAJOR_HASH_SIZE];
static DEFINE_MUTEX(major_names_lock);
@@ -209,7 +209,7 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
* @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
* @major = 0, try to allocate any unused major number.
* @name: the name of the new block device as a zero terminated string
- * @probe: allback that is called on access to any minor number of @major
+ * @probe: callback that is called on access to any minor number of @major
*
* The @name must be unique within the system.
*
@@ -227,7 +227,7 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
* Use register_blkdev instead for any new code.
*/
int __register_blkdev(unsigned int major, const char *name,
- void (*probe)(dev_t devt))
+ int (*probe)(dev_t devt))
{
struct blk_major_name **n, *p;
int index, ret = 0;
@@ -621,17 +621,18 @@ static ssize_t disk_badblocks_store(struct device *dev,
return badblocks_store(disk->bb, page, len, 0);
}
-void blk_request_module(dev_t devt)
+int blk_request_module(dev_t devt)
{
unsigned int major = MAJOR(devt);
struct blk_major_name **n;
+ int err;
mutex_lock(&major_names_lock);
for (n = &major_names[major_to_index(major)]; *n; n = &(*n)->next) {
if ((*n)->major == major && (*n)->probe) {
- (*n)->probe(devt);
+ err = (*n)->probe(devt);
mutex_unlock(&major_names_lock);
- return;
+ return err;
}
}
mutex_unlock(&major_names_lock);
@@ -639,6 +640,8 @@ void blk_request_module(dev_t devt)
if (request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt)) > 0)
/* Make old-style 2.4 aliases work */
request_module("block-major-%d", MAJOR(devt));
+
+ return 0;
}
/*
diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index 5dc9b3d32415..e55824e27188 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -1989,24 +1989,34 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
static DEFINE_MUTEX(ataflop_probe_lock);
-static void ataflop_probe(dev_t dev)
+static int ataflop_probe(dev_t dev)
{
int drive = MINOR(dev) & 3;
int type = MINOR(dev) >> 2;
+ int err = -ENODEV;
if (type)
type--;
- if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
- return;
+ if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS) {
+ err = -EINVAL;
+ goto out;
+ }
+
mutex_lock(&ataflop_probe_lock);
if (!unit[drive].disk[type]) {
- if (ataflop_alloc_disk(drive, type) == 0) {
- add_disk(unit[drive].disk[type]);
+ err = ataflop_alloc_disk(drive, type);
+ if (err == 0) {
+ err = add_disk(unit[drive].disk[type]);
+ if (err)
+ blk_cleanup_disk(unit[drive].disk[type]);
unit[drive].registered[type] = true;
}
}
mutex_unlock(&ataflop_probe_lock);
+
+out:
+ return err;
}
static void atari_cleanup_floppy_disk(struct atari_floppy_struct *fs)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index c2bf4946f4e3..82a93044de95 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -426,10 +426,11 @@ static int brd_alloc(int i)
return err;
}
-static void brd_probe(dev_t dev)
+static int brd_probe(dev_t dev)
{
int i = MINOR(dev) / max_part;
struct brd_device *brd;
+ int err = 0;
mutex_lock(&brd_devices_mutex);
list_for_each_entry(brd, &brd_devices, brd_list) {
@@ -437,9 +438,11 @@ static void brd_probe(dev_t dev)
goto out_unlock;
}
- brd_alloc(i);
+ err = brd_alloc(i);
out_unlock:
mutex_unlock(&brd_devices_mutex);
+
+ return err;
}
static void brd_del_one(struct brd_device *brd)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 0434f28742e7..5ecffc7f6e22 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4517,21 +4517,27 @@ static int floppy_alloc_disk(unsigned int drive, unsigned int type)
static DEFINE_MUTEX(floppy_probe_lock);
-static void floppy_probe(dev_t dev)
+static int floppy_probe(dev_t dev)
{
unsigned int drive = (MINOR(dev) & 3) | ((MINOR(dev) & 0x80) >> 5);
unsigned int type = (MINOR(dev) >> 2) & 0x1f;
+ int err = -ENODEV;
if (drive >= N_DRIVE || !floppy_available(drive) ||
type >= ARRAY_SIZE(floppy_type))
- return;
+ return -EINVAL;
mutex_lock(&floppy_probe_lock);
if (!disks[drive][type]) {
- if (floppy_alloc_disk(drive, type) == 0)
- add_disk(disks[drive][type]);
+ if (floppy_alloc_disk(drive, type) == 0) {
+ err = add_disk(disks[drive][type]);
+ if (err)
+ blk_cleanup_disk(disks[drive][type]);
+ }
}
mutex_unlock(&floppy_probe_lock);
+
+ return err;
}
static int __init do_floppy_init(void)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b8b9e2349e77..6bc1c075741e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2425,13 +2425,13 @@ static void loop_remove(struct loop_device *lo)
kfree(lo);
}
-static void loop_probe(dev_t dev)
+static int loop_probe(dev_t dev)
{
int idx = MINOR(dev) >> part_shift;
if (max_loop && idx >= max_loop)
- return;
- loop_add(idx);
+ return -EINVAL;
+ return loop_add(idx);
}
static int loop_control_remove(int idx)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5c0d3536d7c7..fc2790979686 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5735,12 +5735,16 @@ static int md_alloc(dev_t dev, char *name)
return error;
}
-static void md_probe(dev_t dev)
+static int md_probe(dev_t dev)
{
+ int error = 0;
+
if (MAJOR(dev) == MD_MAJOR && MINOR(dev) >= 512)
- return;
+ return -EINVAL;
if (create_on_open)
- md_alloc(dev, NULL);
+ error = md_alloc(dev, NULL);
+
+ return error;
}
static int add_named_array(const char *val, const struct kernel_param *kp)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 8c1273fff23e..50872c6ce030 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -630,8 +630,9 @@ static struct scsi_driver sd_template = {
* Don't request a new module, as that could deadlock in multipath
* environment.
*/
-static void sd_default_probe(dev_t devt)
+static int sd_default_probe(dev_t devt)
{
+ return 0;
}
/*
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 45df6cbccf12..81a4738910a8 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1144,10 +1144,13 @@ struct block_device *blkdev_get_no_open(dev_t dev)
{
struct block_device *bdev;
struct inode *inode;
+ int ret;
inode = ilookup(blockdev_superblock, dev);
if (!inode) {
- blk_request_module(dev);
+ ret = blk_request_module(dev);
+ if (ret)
+ return NULL;
inode = ilookup(blockdev_superblock, dev);
if (!inode)
return NULL;
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index c68d83c87f83..5828ecda5c49 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -281,7 +281,7 @@ struct gendisk *__blk_alloc_disk(int node, struct lock_class_key *lkclass);
void blk_cleanup_disk(struct gendisk *disk);
int __register_blkdev(unsigned int major, const char *name,
- void (*probe)(dev_t devt));
+ int (*probe)(dev_t devt));
#define register_blkdev(major, name) \
__register_blkdev(major, name, NULL)
void unregister_blkdev(unsigned int major, const char *name);
@@ -317,7 +317,7 @@ static inline int bd_register_pending_holders(struct gendisk *disk)
dev_t part_devt(struct gendisk *disk, u8 partno);
void inc_diskseq(struct gendisk *disk);
dev_t blk_lookup_devt(const char *name, int partno);
-void blk_request_module(dev_t devt);
+int blk_request_module(dev_t devt);
#ifdef CONFIG_BLOCK
void printk_all_partitions(void);
#else /* CONFIG_BLOCK */
--
2.30.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH 2/2] block: add __must_check for *add_disk*() callers
2021-09-04 1:39 [PATCH 0/2] block: 7th -- last batch of add_disk() error handling conversions Luis Chamberlain
2021-09-04 1:39 ` [PATCH 1/2] block: make __register_blkdev() return an error Luis Chamberlain
@ 2021-09-04 1:39 ` Luis Chamberlain
1 sibling, 0 replies; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-04 1:39 UTC (permalink / raw)
To: axboe, hch, efremov, song, jejb, martin.petersen, viro, hare,
jack, ming.lei, tj
Cc: linux-raid, linux-scsi, linux-fsdevel, linux-block, linux-kernel,
Luis Chamberlain
Now that we have done a spring cleaning on all drivers and added
error checking / handling, let's keep it that way and ensure
no new drivers fail to stick with it.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
block/genhd.c | 6 +++---
include/linux/genhd.h | 6 +++---
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index c4836296a974..4c80e6c3d8dd 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -383,8 +383,8 @@ static void disk_scan_partitions(struct gendisk *disk)
* This function registers the partitioning information in @disk
* with the kernel.
*/
-int device_add_disk(struct device *parent, struct gendisk *disk,
- const struct attribute_group **groups)
+int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
+ const struct attribute_group **groups)
{
struct device *ddev = disk_to_dev(disk);
@@ -529,7 +529,7 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
out_free_ext_minor:
if (disk->major == BLOCK_EXT_MAJOR)
blk_free_ext_minor(disk->first_minor);
- return WARN_ON_ONCE(ret); /* keep until all callers handle errors */
+ return ret;
}
EXPORT_SYMBOL(device_add_disk);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 5828ecda5c49..8d78d36c424e 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -214,9 +214,9 @@ static inline dev_t disk_devt(struct gendisk *disk)
void disk_uevent(struct gendisk *disk, enum kobject_action action);
/* block/genhd.c */
-int device_add_disk(struct device *parent, struct gendisk *disk,
- const struct attribute_group **groups);
-static inline int add_disk(struct gendisk *disk)
+int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
+ const struct attribute_group **groups);
+static inline int __must_check add_disk(struct gendisk *disk)
{
return device_add_disk(NULL, disk, NULL);
}
--
2.30.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-04 1:39 ` [PATCH 1/2] block: make __register_blkdev() return an error Luis Chamberlain
@ 2021-09-04 2:49 ` Tetsuo Handa
2021-09-04 4:14 ` Jens Axboe
2021-09-05 18:11 ` Luis Chamberlain
0 siblings, 2 replies; 11+ messages in thread
From: Tetsuo Handa @ 2021-09-04 2:49 UTC (permalink / raw)
To: Luis Chamberlain, axboe, hch; +Cc: linux-block
On 2021/09/04 10:39, Luis Chamberlain wrote:
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 45df6cbccf12..81a4738910a8 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1144,10 +1144,13 @@ struct block_device *blkdev_get_no_open(dev_t dev)
> {
> struct block_device *bdev;
> struct inode *inode;
> + int ret;
>
> inode = ilookup(blockdev_superblock, dev);
> if (!inode) {
> - blk_request_module(dev);
> + ret = blk_request_module(dev);
> + if (ret)
> + return NULL;
Since e.g. loop_add() from loop_probe() returns -EEXIST when /dev/loop$num already
exists (e.g. raced with ioctl(LOOP_CTL_ADD)), isn't unconditionally failing an over-failing?
> inode = ilookup(blockdev_superblock, dev);
> if (!inode)
> return NULL;
By the way, Jens, will you pick up
https://lkml.kernel.org/r/adb1e792-fc0e-ee81-7ea0-0906fc36419d@i-love.sakura.ne.jp
before these "add error handling" changes?
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-04 2:49 ` Tetsuo Handa
@ 2021-09-04 4:14 ` Jens Axboe
2021-09-05 18:11 ` Luis Chamberlain
1 sibling, 0 replies; 11+ messages in thread
From: Jens Axboe @ 2021-09-04 4:14 UTC (permalink / raw)
To: Tetsuo Handa, Luis Chamberlain, hch; +Cc: linux-block
On 9/3/21 8:49 PM, Tetsuo Handa wrote:
> By the way, Jens, will you pick up
> https://lkml.kernel.org/r/adb1e792-fc0e-ee81-7ea0-0906fc36419d@i-love.sakura.ne.jp
> before these "add error handling" changes?
Yes, that one is 5.15 material, the rest of the error handling changes
are not. Hence the ordering follows naturally from that.
--
Jens Axboe
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-04 2:49 ` Tetsuo Handa
2021-09-04 4:14 ` Jens Axboe
@ 2021-09-05 18:11 ` Luis Chamberlain
2021-09-06 5:59 ` Tetsuo Handa
1 sibling, 1 reply; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-05 18:11 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: axboe, hch, linux-block
On Sat, Sep 04, 2021 at 11:49:06AM +0900, Tetsuo Handa wrote:
> On 2021/09/04 10:39, Luis Chamberlain wrote:
> > diff --git a/fs/block_dev.c b/fs/block_dev.c
> > index 45df6cbccf12..81a4738910a8 100644
> > --- a/fs/block_dev.c
> > +++ b/fs/block_dev.c
> > @@ -1144,10 +1144,13 @@ struct block_device *blkdev_get_no_open(dev_t dev)
> > {
> > struct block_device *bdev;
> > struct inode *inode;
> > + int ret;
> >
> > inode = ilookup(blockdev_superblock, dev);
> > if (!inode) {
> > - blk_request_module(dev);
> > + ret = blk_request_module(dev);
> > + if (ret)
> > + return NULL;
>
> Since e.g. loop_add() from loop_probe() returns -EEXIST when /dev/loop$num already
> exists (e.g. raced with ioctl(LOOP_CTL_ADD)), isn't unconditionally failing an over-failing?
It's not clear to me how. What do we loose by capturing the failure on
blk_request_module()?
Luis
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-05 18:11 ` Luis Chamberlain
@ 2021-09-06 5:59 ` Tetsuo Handa
2021-09-07 14:57 ` Luis Chamberlain
0 siblings, 1 reply; 11+ messages in thread
From: Tetsuo Handa @ 2021-09-06 5:59 UTC (permalink / raw)
To: Luis Chamberlain; +Cc: axboe, hch, linux-block
On 2021/09/06 3:11, Luis Chamberlain wrote:
> On Sat, Sep 04, 2021 at 11:49:06AM +0900, Tetsuo Handa wrote:
>> On 2021/09/04 10:39, Luis Chamberlain wrote:
>>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>>> index 45df6cbccf12..81a4738910a8 100644
>>> --- a/fs/block_dev.c
>>> +++ b/fs/block_dev.c
>>> @@ -1144,10 +1144,13 @@ struct block_device *blkdev_get_no_open(dev_t dev)
>>> {
>>> struct block_device *bdev;
>>> struct inode *inode;
>>> + int ret;
>>>
>>> inode = ilookup(blockdev_superblock, dev);
>>> if (!inode) {
>>> - blk_request_module(dev);
>>> + ret = blk_request_module(dev);
>>> + if (ret)
>>> + return NULL;
>>
>> Since e.g. loop_add() from loop_probe() returns -EEXIST when /dev/loop$num already
>> exists (e.g. raced with ioctl(LOOP_CTL_ADD)), isn't unconditionally failing an over-failing?
>
> It's not clear to me how. What do we loose by capturing the failure on
> blk_request_module()?
>
We loose ability to handle concurrent request.
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 45df6cbccf12..9559c8aabc88 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -36,6 +36,7 @@
#include <linux/suspend.h>
#include "internal.h"
#include "../block/blk.h"
+#include <linux/debug_locks.h>
struct bdev_inode {
struct block_device bdev;
@@ -1147,7 +1148,11 @@ struct block_device *blkdev_get_no_open(dev_t dev)
inode = ilookup(blockdev_superblock, dev);
if (!inode) {
+ dump_stack();
+ debug_show_held_locks(current);
blk_request_module(dev);
+ if (!strcmp(current->comm, "cat"))
+ schedule_timeout_killable(10 * HZ);
inode = ilookup(blockdev_superblock, dev);
if (!inode)
return NULL;
Try "mknod /dev/loop$num b 7 $num" followed by concurrent "cat /dev/loop$num" requests.
[ 535.847823] [ T5261] CPU: 1 PID: 5261 Comm: cat Tainted: G E 5.14.0-next-20210903+ #3
[ 535.851419] [ T5261] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
[ 535.855563] [ T5261] Call Trace:
[ 535.856746] [ T5261] dump_stack_lvl+0x79/0xbf
[ 535.858332] [ T5261] blkdev_get_no_open+0x86/0xe0
[ 535.860036] [ T5261] blkdev_get_by_dev+0x5f/0x540
[ 535.861747] [ T5261] ? block_ioctl+0x40/0x40
[ 535.863305] [ T5261] blkdev_open+0x58/0x90
[ 535.864865] [ T5261] do_dentry_open+0x144/0x3a0
[ 535.866538] [ T5261] path_openat+0xa57/0xda0
[ 535.868139] [ T5261] do_filp_open+0x9f/0x140
[ 535.869933] [ T5261] ? _raw_spin_unlock+0x1a/0x30
[ 535.871570] [ T5261] do_sys_openat2+0x71/0x150
[ 535.873195] [ T5261] __x64_sys_openat+0x78/0xa0
[ 535.874740] [ T5261] do_syscall_64+0x3d/0xb0
[ 535.876234] [ T5261] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 535.878428] [ T5261] RIP: 0033:0x7f6b997d28db
[ 535.879927] [ T5261] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 2b 0c 25
[ 535.886778] [ T5261] RSP: 002b:00007ffe8bdad880 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
[ 535.889727] [ T5261] RAX: ffffffffffffffda RBX: 000055f741e5b634 RCX: 00007f6b997d28db
[ 535.892466] [ T5261] RDX: 0000000000000000 RSI: 00007ffe8bdaf764 RDI: 00000000ffffff9c
[ 535.895226] [ T5261] RBP: 00007ffe8bdaf764 R08: 0000000000000001 R09: 0000000000000000
[ 535.898162] [ T5261] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 535.900858] [ T5261] R13: 00007ffe8bdadb68 R14: 0000000000000000 R15: 0000000000020000
[ 535.903752] [ T5262] CPU: 2 PID: 5262 Comm: cat Tainted: G E 5.14.0-next-20210903+ #3
[ 535.904759] [ T5261] no locks held by cat/5261.
[ 535.906905] [ T5262] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
[ 535.906908] [ T5262] Call Trace:
[ 535.906912] [ T5262] dump_stack_lvl+0x79/0xbf
[ 535.915279] [ T5262] blkdev_get_no_open+0x86/0xe0
[ 535.916942] [ T5262] blkdev_get_by_dev+0x5f/0x540
[ 535.918608] [ T5262] ? block_ioctl+0x40/0x40
[ 535.920250] [ T5262] blkdev_open+0x58/0x90
[ 535.921696] [ T5262] do_dentry_open+0x144/0x3a0
[ 535.923291] [ T5262] path_openat+0xa57/0xda0
[ 535.924816] [ T5262] do_filp_open+0x9f/0x140
[ 535.926359] [ T5262] ? _raw_spin_unlock+0x1a/0x30
[ 535.928030] [ T5262] do_sys_openat2+0x71/0x150
[ 535.929600] [ T5262] __x64_sys_openat+0x78/0xa0
[ 535.931215] [ T5262] do_syscall_64+0x3d/0xb0
[ 535.932768] [ T5262] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 535.934817] [ T5262] RIP: 0033:0x7efe3a0aa8db
[ 535.936354] [ T5262] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 2b 0c 25
[ 535.943021] [ T5262] RSP: 002b:00007ffe1697dfb0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
[ 535.945883] [ T5262] RAX: ffffffffffffffda RBX: 000055982a4e1634 RCX: 00007efe3a0aa8db
[ 535.948580] [ T5262] RDX: 0000000000000000 RSI: 00007ffe1697e764 RDI: 00000000ffffff9c
[ 535.951298] [ T5262] RBP: 00007ffe1697e764 R08: 0000000000000001 R09: 0000000000000000
[ 535.954064] [ T5262] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 535.956789] [ T5262] R13: 00007ffe1697e298 R14: 0000000000000000 R15: 0000000000020000
[ 535.959522] [ T5263] CPU: 0 PID: 5263 Comm: cat Tainted: G E 5.14.0-next-20210903+ #3
[ 535.962995] [ T5263] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
[ 535.965787] [ T5262] no locks held by cat/5262.
[ 535.966998] [ T5263] Call Trace:
[ 535.970068] [ T5263] dump_stack_lvl+0x79/0xbf
[ 535.971572] [ T5263] blkdev_get_no_open+0x86/0xe0
[ 535.973199] [ T5263] blkdev_get_by_dev+0x5f/0x540
[ 535.974893] [ T5263] ? block_ioctl+0x40/0x40
[ 535.976364] [ T5263] blkdev_open+0x58/0x90
[ 535.977781] [ T5263] do_dentry_open+0x144/0x3a0
[ 535.979378] [ T5263] path_openat+0xa57/0xda0
[ 535.980882] [ T5263] do_filp_open+0x9f/0x140
[ 535.982333] [ T5263] ? _raw_spin_unlock+0x1a/0x30
[ 535.984002] [ T5263] do_sys_openat2+0x71/0x150
[ 535.985554] [ T5263] __x64_sys_openat+0x78/0xa0
[ 535.987232] [ T5263] do_syscall_64+0x3d/0xb0
[ 535.988790] [ T5263] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 535.990804] [ T5263] RIP: 0033:0x7ff84ab408db
[ 535.992275] [ T5263] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 2b 0c 25
[ 535.998888] [ T5263] RSP: 002b:00007ffda9b89a70 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
[ 536.001628] [ T5263] RAX: ffffffffffffffda RBX: 000055626f376634 RCX: 00007ff84ab408db
[ 536.004350] [ T5263] RDX: 0000000000000000 RSI: 00007ffda9b8a764 RDI: 00000000ffffff9c
[ 536.007009] [ T5263] RBP: 00007ffda9b8a764 R08: 0000000000000001 R09: 0000000000000000
[ 536.009753] [ T5263] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 536.012493] [ T5263] R13: 00007ffda9b89d58 R14: 0000000000000000 R15: 0000000000020000
[ 536.015854] [ T5263] no locks held by cat/5263.
If blk_request_module() does not ignore -EEXIST error, only the first open() request would succeed
because loop_add() returns 0 and all other concurrent requests would fail because loop_add() returns -EEXIST.
Actually, blk_request_module() failures should be ignored, for subsequent ilookup() will
fail if blk_request_module() failed to create the requested block device.
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-06 5:59 ` Tetsuo Handa
@ 2021-09-07 14:57 ` Luis Chamberlain
2021-09-07 15:23 ` Tetsuo Handa
0 siblings, 1 reply; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-07 14:57 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: axboe, hch, linux-block
On Mon, Sep 06, 2021 at 02:59:38PM +0900, Tetsuo Handa wrote:
> On 2021/09/06 3:11, Luis Chamberlain wrote:
> > On Sat, Sep 04, 2021 at 11:49:06AM +0900, Tetsuo Handa wrote:
> >> On 2021/09/04 10:39, Luis Chamberlain wrote:
> >>> diff --git a/fs/block_dev.c b/fs/block_dev.c
> >>> index 45df6cbccf12..81a4738910a8 100644
> >>> --- a/fs/block_dev.c
> >>> +++ b/fs/block_dev.c
> >>> @@ -1144,10 +1144,13 @@ struct block_device *blkdev_get_no_open(dev_t dev)
> >>> {
> >>> struct block_device *bdev;
> >>> struct inode *inode;
> >>> + int ret;
> >>>
> >>> inode = ilookup(blockdev_superblock, dev);
> >>> if (!inode) {
> >>> - blk_request_module(dev);
> >>> + ret = blk_request_module(dev);
> >>> + if (ret)
> >>> + return NULL;
> >>
> >> Since e.g. loop_add() from loop_probe() returns -EEXIST when /dev/loop$num already
> >> exists (e.g. raced with ioctl(LOOP_CTL_ADD)), isn't unconditionally failing an over-failing?
> >
> > It's not clear to me how. What do we loose by capturing the failure on
> > blk_request_module()?
> >
>
> We loose ability to handle concurrent request.
> If blk_request_module() does not ignore -EEXIST error, only the first
> open() request would succeed because loop_add() returns 0 and all
> other concurrent requests would fail because loop_add() returns
> -EEXIST.
Yes I see that now thanks!
> Actually, blk_request_module() failures should be ignored, for
> subsequent ilookup() will fail if blk_request_module() failed to
> create the requested block device.
Then how about this:
Since we would like to use __must_check for add_disk() we proceed with
the change to capture the errors and propagate them and we just document on
fs/block_dev.c's use of blk_request_module() about the above issue and
how we prefer the errror that ilookup() would return.
Luis
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-07 14:57 ` Luis Chamberlain
@ 2021-09-07 15:23 ` Tetsuo Handa
2021-09-07 15:28 ` Luis Chamberlain
0 siblings, 1 reply; 11+ messages in thread
From: Tetsuo Handa @ 2021-09-07 15:23 UTC (permalink / raw)
To: Luis Chamberlain; +Cc: axboe, hch, linux-block
On 2021/09/07 23:57, Luis Chamberlain wrote:
>> Actually, blk_request_module() failures should be ignored, for
>> subsequent ilookup() will fail if blk_request_module() failed to
>> create the requested block device.
>
> Then how about this:
>
> Since we would like to use __must_check for add_disk() we proceed with
> the change to capture the errors and propagate them and we just document on
> fs/block_dev.c's use of blk_request_module() about the above issue and
> how we prefer the errror that ilookup() would return.
Marking add_disk() as __must_check makes it possible to enforce "don't leave
partially initialized devices". That's already an enough improvement.
Probe functions can remain "void", and hence blk_request_module() can remain "void".
That is, I would drop "[PATCH 1/2] block: make __register_blkdev() return an error".
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-07 15:23 ` Tetsuo Handa
@ 2021-09-07 15:28 ` Luis Chamberlain
2021-09-08 14:00 ` Luis Chamberlain
0 siblings, 1 reply; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-07 15:28 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: axboe, hch, linux-block
On Wed, Sep 08, 2021 at 12:23:02AM +0900, Tetsuo Handa wrote:
> On 2021/09/07 23:57, Luis Chamberlain wrote:
> >> Actually, blk_request_module() failures should be ignored, for
> >> subsequent ilookup() will fail if blk_request_module() failed to
> >> create the requested block device.
> >
> > Then how about this:
> >
> > Since we would like to use __must_check for add_disk() we proceed with
> > the change to capture the errors and propagate them and we just document on
> > fs/block_dev.c's use of blk_request_module() about the above issue and
> > how we prefer the errror that ilookup() would return.
>
> Marking add_disk() as __must_check makes it possible to enforce "don't leave
> partially initialized devices". That's already an enough improvement.
>
> Probe functions can remain "void", and hence blk_request_module() can remain "void".
> That is, I would drop "[PATCH 1/2] block: make __register_blkdev() return an error".
Probe calls can be left voide, but because of the new __must_check we'd
still have to modify all probe calls as they use add_disk() and it would
seem odd to just capture the error to ignore it without documenting
any of this.
Luis
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 1/2] block: make __register_blkdev() return an error
2021-09-07 15:28 ` Luis Chamberlain
@ 2021-09-08 14:00 ` Luis Chamberlain
0 siblings, 0 replies; 11+ messages in thread
From: Luis Chamberlain @ 2021-09-08 14:00 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: axboe, hch, linux-block
On Tue, Sep 07, 2021 at 08:28:06AM -0700, Luis Chamberlain wrote:
> On Wed, Sep 08, 2021 at 12:23:02AM +0900, Tetsuo Handa wrote:
> > On 2021/09/07 23:57, Luis Chamberlain wrote:
> > >> Actually, blk_request_module() failures should be ignored, for
> > >> subsequent ilookup() will fail if blk_request_module() failed to
> > >> create the requested block device.
> > >
> > > Then how about this:
> > >
> > > Since we would like to use __must_check for add_disk() we proceed with
> > > the change to capture the errors and propagate them and we just document on
> > > fs/block_dev.c's use of blk_request_module() about the above issue and
> > > how we prefer the errror that ilookup() would return.
> >
> > Marking add_disk() as __must_check makes it possible to enforce "don't leave
> > partially initialized devices". That's already an enough improvement.
> >
> > Probe functions can remain "void", and hence blk_request_module() can remain "void".
> > That is, I would drop "[PATCH 1/2] block: make __register_blkdev() return an error".
>
> Probe calls can be left voide, but because of the new __must_check we'd
> still have to modify all probe calls as they use add_disk() and it would
> seem odd to just capture the error to ignore it without documenting
> any of this.
So indeed, all probe() routines would need to be modified anyway because
of the added final __must_check. Because of this I still think that if
we want to *ignore* the error, we should just document and ignore it on
the caller side. That is, still modify __register_blkdev() to propagate
the error, and the caller can decide to ignore or not. In this case
we can document on fs/block_dev.c *why* we are ignoring the error.
Thoughts?
Luis
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2021-09-08 14:00 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-04 1:39 [PATCH 0/2] block: 7th -- last batch of add_disk() error handling conversions Luis Chamberlain
2021-09-04 1:39 ` [PATCH 1/2] block: make __register_blkdev() return an error Luis Chamberlain
2021-09-04 2:49 ` Tetsuo Handa
2021-09-04 4:14 ` Jens Axboe
2021-09-05 18:11 ` Luis Chamberlain
2021-09-06 5:59 ` Tetsuo Handa
2021-09-07 14:57 ` Luis Chamberlain
2021-09-07 15:23 ` Tetsuo Handa
2021-09-07 15:28 ` Luis Chamberlain
2021-09-08 14:00 ` Luis Chamberlain
2021-09-04 1:39 ` [PATCH 2/2] block: add __must_check for *add_disk*() callers Luis Chamberlain
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