[PATCH RESEND v11] Add cli and ioctl to forget scanned device(s)

[PATCH RESEND v11] Add cli and ioctl to forget scanned device(s)

[Anand Jain]

v11:
 btrfs-progs: Bring the code into the else part of if(forget).
	      Use strerror to print the erorr instead of ret.

v10:
 Make btrfs-progs changes more readable.
 With an effort to keep the known bug [1] as it is..
  [1]
   The cli 'btrfs device scan --all /dev/sdb' which should have scanned
    only one device, ends up scanning all the devices and I am not trying
    to fix this bug in this patch because..
  . -d|--all is marked as deprecated, I hope -d option would go away
  . For now some script might be using this bug as a feature, and fixing
    this bug might lead to mount failure.

v9:
 Make forget as a btrfs device scan option.
 Use forget in the fstests, now you can run fstests with btrfs as rootfs
  which helps to exercise the uuid_mutex lock.

v8:
 Change log update in the kernel patch.

v7:
 Use struct btrfs_ioctl_vol_args (instead of struct
  btrfs_ioctl_vol_args_v2) as its inline with other ioctl
  btrfs-control
 The CLI usage/features remains same. However internally the ioctl flag
  is not required to delete all the unmounted devices. Instead leave
  btrfs_ioctl_vol_args::name NULL.

v6:
 Use the changed fn name btrfs_free_stale_devices().

 Change in title:
 Old v5:
 Cover-letter:
  [PATCH v5] Add cli and ioctl to ignore a scanned device
 Kernel:
  [PATCH v5] btrfs: introduce feature to ignore a btrfs device
 Progs:
  [PATCH v5] btrfs-progs: add 'btrfs device ignore' cli

v5:
  Adds feature to delete all stale devices
  Reuses btrfs_free_stale_devices() fn and so depends on the
    patch-set [1] in the ML.
  Uses struct btrfs_ioctl_vol_args_v2 instead of
    struct btrfs_ioctl_vol_args as arg
  Does the device path matching instead of btrfs_device matching
    (we won't delete the mounted device as btrfs_free_stale_devices()
    checks for it)
v4:
  No change. But as the ML thread may be confusing, so resend.
v3:
  No change. Send to correct ML.
v2:
  Accepts review from Nikolay, details are in the specific patch.
  Patch 1/2 is renamed from
    [PATCH 1/2] btrfs: refactor btrfs_free_stale_device() to get device list delete
  to
    [PATCH 1/2] btrfs: add function to device list delete

Adds cli and ioctl to forget a scanned device or forget all stale
devices in the kernel.


Anand Jain (1):
  btrfs: introduce feature to forget a btrfs device

 fs/btrfs/super.c           | 3 +++
 fs/btrfs/volumes.c         | 9 +++++++++
 fs/btrfs/volumes.h         | 1 +
 include/uapi/linux/btrfs.h | 2 ++
 4 files changed, 15 insertions(+)

Anand Jain (1):
  btrfs-progs: add cli to forget one or all scanned devices

 cmds-device.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++---------
 ioctl.h       |  2 ++
 2 files changed, 56 insertions(+), 9 deletions(-)

[1]
Anand Jain (1):
  fstests: btrfs use forget if not reload

 common/btrfs    | 20 ++++++++++++++++++++
 tests/btrfs/124 |  6 +++---
 tests/btrfs/125 |  6 +++---
 tests/btrfs/154 |  6 +++---
 tests/btrfs/164 |  4 ++--
 5 files changed, 31 insertions(+), 11 deletions(-)

-- 
1.8.3.1

[PATCH] btrfs: introduce feature to forget a btrfs device

[Anand Jain]

Support for a new command 'btrfs dev forget [dev]' is proposed here
to undo the effects of 'btrfs dev scan [dev]'. For this purpose
this patch proposes to use ioctl #5 as it was empty.
	IOW(BTRFS_IOCTL_MAGIC, 5, ..)
This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
the /dev/btrfs-control to forget one or all devices, (devices which are
not mounted) from the btrfs kernel.

The argument it takes is struct btrfs_ioctl_vol_args, and ::name can be
set to specify the device path. And all unmounted devices can be removed
from the kernel if no device path is provided.

Again, the devices are removed only if the relevant fsid aren't mounted.

This new cli can provide..
 . Release of unwanted btrfs_fs_devices and btrfs_devices memory if the
   device is not going to be mounted.
 . Ability to mount the device in degraded mode when one of the other
   device is corrupted like in split brain raid1.
 . Running test cases which requires btrfs.ko-reload if the rootfs
   is btrfs.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/super.c           | 3 +++
 fs/btrfs/volumes.c         | 9 +++++++++
 fs/btrfs/volumes.h         | 1 +
 include/uapi/linux/btrfs.h | 2 ++
 4 files changed, 15 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 345c64d810d4..f99db6899004 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2246,6 +2246,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 		ret = PTR_ERR_OR_ZERO(device);
 		mutex_unlock(&uuid_mutex);
 		break;
+	case BTRFS_IOC_FORGET_DEV:
+		ret = btrfs_forget_devices(vol->name);
+		break;
 	case BTRFS_IOC_DEVICES_READY:
 		mutex_lock(&uuid_mutex);
 		device = btrfs_scan_one_device(vol->name, FMODE_READ,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f435d397019e..e1365a122657 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1208,6 +1208,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
 	return 0;
 }
 
+int btrfs_forget_devices(const char *path)
+{
+	mutex_lock(&uuid_mutex);
+	btrfs_free_stale_devices(strlen(path) ? path:NULL, NULL);
+	mutex_unlock(&uuid_mutex);
+
+	return 0;
+}
+
 /*
  * Look for a btrfs signature on a device. This may be called out of the mount path
  * and we are not allowed to call set_blocksize during the scan. The superblock
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index aefce895e994..180297d04938 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -406,6 +406,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
 struct btrfs_device *btrfs_scan_one_device(const char *path,
 					   fmode_t flags, void *holder);
+int btrfs_forget_devices(const char *path);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
 void btrfs_assign_next_active_device(struct btrfs_device *device,
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 5ca1d21fc4a7..b1be7f828cb4 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -836,6 +836,8 @@ enum btrfs_err_code {
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
 				   struct btrfs_ioctl_vol_args)
+#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
+				   struct btrfs_ioctl_vol_args)
 /* trans start and trans end are dangerous, and only for
  * use by applications that know how to avoid the
  * resulting deadlocks
-- 
1.8.3.1

[PATCH] btrfs-progs: add cli to forget one or all scanned devices

[Anand Jain]

This patch adds cli
  btrfs device forget [dev]
to remove the given device structure in the kernel if the device
is unmounted. If no argument is given it shall remove all stale
(device which are not mounted) from the kernel.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
---
 cmds-device.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
 ioctl.h       |  2 ++
 2 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/cmds-device.c b/cmds-device.c
index 2a05f70a76a9..280d6f555377 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -254,10 +254,32 @@ static int cmd_device_delete(int argc, char **argv)
 	return _cmd_device_remove(argc, argv, cmd_device_delete_usage);
 }
 
+static int btrfs_forget_devices(char *path)
+{
+	struct btrfs_ioctl_vol_args args;
+	int ret;
+	int fd;
+
+	fd = open("/dev/btrfs-control", O_RDWR);
+	if (fd < 0)
+		return -errno;
+
+	memset(&args, 0, sizeof(args));
+	if (path)
+		strncpy_null(args.name, path);
+	ret = ioctl(fd, BTRFS_IOC_FORGET_DEV, &args);
+	if (ret)
+		ret = -errno;
+	close(fd);
+	return ret;
+}
+
 static const char * const cmd_device_scan_usage[] = {
-	"btrfs device scan [(-d|--all-devices)|<device> [<device>...]]",
-	"Scan devices for a btrfs filesystem",
+	"btrfs device scan [(-d|--all-devices)|(-u|--forget)|<device> "\
+							"[<device>...]]",
+	"Scan or forget (deregister) devices for a btrfs filesystem",
 	" -d|--all-devices (deprecated)",
+	" -u|--forget [<device> ..]",
 	NULL
 };
 
@@ -267,37 +289,53 @@ static int cmd_device_scan(int argc, char **argv)
 	int devstart;
 	int all = 0;
 	int ret = 0;
+	int forget = 0;
 
 	optind = 0;
 	while (1) {
 		int c;
 		static const struct option long_options[] = {
 			{ "all-devices", no_argument, NULL, 'd'},
+			{ "forget", no_argument, NULL, 'u'},
 			{ NULL, 0, NULL, 0}
 		};
 
-		c = getopt_long(argc, argv, "d", long_options, NULL);
+		c = getopt_long(argc, argv, "du", long_options, NULL);
 		if (c < 0)
 			break;
 		switch (c) {
 		case 'd':
 			all = 1;
 			break;
+		case 'u':
+			forget = 1;
+			break;
 		default:
 			usage(cmd_device_scan_usage);
 		}
 	}
 	devstart = optind;
 
+	if (all && forget)
+		usage(cmd_device_scan_usage);
+
 	if (all && check_argc_max(argc - optind, 1))
 		usage(cmd_device_scan_usage);
 
 	if (all || argc - optind == 0) {
-		printf("Scanning for Btrfs filesystems\n");
-		ret = btrfs_scan_devices();
-		error_on(ret, "error %d while scanning", ret);
-		ret = btrfs_register_all_devices();
-		error_on(ret, "there are %d errors while registering devices", ret);
+		if (forget) {
+			ret = btrfs_forget_devices(NULL);
+			error_on(ret, "'%s', forget failed",
+				 strerror(-ret));
+		} else {
+			printf("Scanning for Btrfs filesystems\n");
+			ret = btrfs_scan_devices();
+			error_on(ret, "error %d while scanning", ret);
+			ret = btrfs_register_all_devices();
+			error_on(ret,
+				"there are %d errors while registering devices",
+				ret);
+		}
 		goto out;
 	}
 
@@ -315,11 +353,19 @@ static int cmd_device_scan(int argc, char **argv)
 			ret = 1;
 			goto out;
 		}
-		printf("Scanning for Btrfs filesystems in '%s'\n", path);
-		if (btrfs_register_one_device(path) != 0) {
-			ret = 1;
-			free(path);
-			goto out;
+		if (forget) {
+			ret = btrfs_forget_devices(path);
+			if (ret)
+				error("Can't forget '%s': %s",
+							path, strerror(-ret));
+		} else {
+			printf("Scanning for Btrfs filesystems in '%s'\n",
+									path);
+			if (btrfs_register_one_device(path) != 0) {
+				ret = 1;
+				free(path);
+				goto out;
+			}
 		}
 		free(path);
 	}
diff --git a/ioctl.h b/ioctl.h
index 709e996f401c..e27d80e09392 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -721,6 +721,8 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
 				   struct btrfs_ioctl_vol_args)
+#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
+				   struct btrfs_ioctl_vol_args)
 /* trans start and trans end are dangerous, and only for
  * use by applications that know how to avoid the
  * resulting deadlocks
-- 
1.8.3.1

Re: [PATCH] btrfs: introduce feature to forget a btrfs device

[Filipe Manana]

On Wed, Nov 14, 2018 at 9:14 AM Anand Jain <anand.jain@oracle.com> wrote:
>
> Support for a new command 'btrfs dev forget [dev]' is proposed here
> to undo the effects of 'btrfs dev scan [dev]'. For this purpose
> this patch proposes to use ioctl #5 as it was empty.
>         IOW(BTRFS_IOCTL_MAGIC, 5, ..)
> This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
> the /dev/btrfs-control to forget one or all devices, (devices which are
> not mounted) from the btrfs kernel.
>
> The argument it takes is struct btrfs_ioctl_vol_args, and ::name can be
> set to specify the device path. And all unmounted devices can be removed
> from the kernel if no device path is provided.
>
> Again, the devices are removed only if the relevant fsid aren't mounted.
>
> This new cli can provide..
>  . Release of unwanted btrfs_fs_devices and btrfs_devices memory if the
>    device is not going to be mounted.
>  . Ability to mount the device in degraded mode when one of the other
>    device is corrupted like in split brain raid1.
>  . Running test cases which requires btrfs.ko-reload if the rootfs
>    is btrfs.
>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/super.c           | 3 +++
>  fs/btrfs/volumes.c         | 9 +++++++++
>  fs/btrfs/volumes.h         | 1 +
>  include/uapi/linux/btrfs.h | 2 ++
>  4 files changed, 15 insertions(+)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 345c64d810d4..f99db6899004 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2246,6 +2246,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>                 ret = PTR_ERR_OR_ZERO(device);
>                 mutex_unlock(&uuid_mutex);
>                 break;
> +       case BTRFS_IOC_FORGET_DEV:
> +               ret = btrfs_forget_devices(vol->name);
> +               break;
>         case BTRFS_IOC_DEVICES_READY:
>                 mutex_lock(&uuid_mutex);
>                 device = btrfs_scan_one_device(vol->name, FMODE_READ,
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index f435d397019e..e1365a122657 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1208,6 +1208,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>         return 0;
>  }
>
> +int btrfs_forget_devices(const char *path)
> +{
> +       mutex_lock(&uuid_mutex);
> +       btrfs_free_stale_devices(strlen(path) ? path:NULL, NULL);

One space before : and another one after it please.

Now the more important: don't use strlen, use strnlen. Some malicious
or sloppy user might have passed a non-null terminated string, you
don't want strlen to go past the limits of btrfs_ioctl_vol_args for
obvious reasons.

Also, please, not just to make a maintainer's life easier, but current
and future reviewers, add the patch version to each patch's subject
and not just the cover letter. Also list (after ---) what changes
between each patch version in the patch itself and not the cover
letter.

V12, here we go.

> +       mutex_unlock(&uuid_mutex);
> +
> +       return 0;
> +}
> +
>  /*
>   * Look for a btrfs signature on a device. This may be called out of the mount path
>   * and we are not allowed to call set_blocksize during the scan. The superblock
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index aefce895e994..180297d04938 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -406,6 +406,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>                        fmode_t flags, void *holder);
>  struct btrfs_device *btrfs_scan_one_device(const char *path,
>                                            fmode_t flags, void *holder);
> +int btrfs_forget_devices(const char *path);
>  int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>  void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>  void btrfs_assign_next_active_device(struct btrfs_device *device,
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index 5ca1d21fc4a7..b1be7f828cb4 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -836,6 +836,8 @@ enum btrfs_err_code {
>                                    struct btrfs_ioctl_vol_args)
>  #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
>                                    struct btrfs_ioctl_vol_args)
> +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
> +                                  struct btrfs_ioctl_vol_args)
>  /* trans start and trans end are dangerous, and only for
>   * use by applications that know how to avoid the
>   * resulting deadlocks
> --
> 1.8.3.1
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

Re: [PATCH] btrfs: introduce feature to forget a btrfs device

[Filipe Manana]

On Wed, Nov 14, 2018 at 11:15 AM Filipe Manana <fdmanana@gmail.com> wrote:
>
> On Wed, Nov 14, 2018 at 9:14 AM Anand Jain <anand.jain@oracle.com> wrote:
> >
> > Support for a new command 'btrfs dev forget [dev]' is proposed here
> > to undo the effects of 'btrfs dev scan [dev]'. For this purpose
> > this patch proposes to use ioctl #5 as it was empty.
> >         IOW(BTRFS_IOCTL_MAGIC, 5, ..)
> > This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
> > the /dev/btrfs-control to forget one or all devices, (devices which are
> > not mounted) from the btrfs kernel.
> >
> > The argument it takes is struct btrfs_ioctl_vol_args, and ::name can be
> > set to specify the device path. And all unmounted devices can be removed
> > from the kernel if no device path is provided.
> >
> > Again, the devices are removed only if the relevant fsid aren't mounted.
> >
> > This new cli can provide..
> >  . Release of unwanted btrfs_fs_devices and btrfs_devices memory if the
> >    device is not going to be mounted.
> >  . Ability to mount the device in degraded mode when one of the other
> >    device is corrupted like in split brain raid1.
> >  . Running test cases which requires btrfs.ko-reload if the rootfs
> >    is btrfs.
> >
> > Signed-off-by: Anand Jain <anand.jain@oracle.com>
> > Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> > ---
> >  fs/btrfs/super.c           | 3 +++
> >  fs/btrfs/volumes.c         | 9 +++++++++
> >  fs/btrfs/volumes.h         | 1 +
> >  include/uapi/linux/btrfs.h | 2 ++
> >  4 files changed, 15 insertions(+)
> >
> > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> > index 345c64d810d4..f99db6899004 100644
> > --- a/fs/btrfs/super.c
> > +++ b/fs/btrfs/super.c
> > @@ -2246,6 +2246,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
> >                 ret = PTR_ERR_OR_ZERO(device);
> >                 mutex_unlock(&uuid_mutex);
> >                 break;
> > +       case BTRFS_IOC_FORGET_DEV:
> > +               ret = btrfs_forget_devices(vol->name);
> > +               break;
> >         case BTRFS_IOC_DEVICES_READY:
> >                 mutex_lock(&uuid_mutex);
> >                 device = btrfs_scan_one_device(vol->name, FMODE_READ,
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index f435d397019e..e1365a122657 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -1208,6 +1208,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
> >         return 0;
> >  }
> >
> > +int btrfs_forget_devices(const char *path)
> > +{
> > +       mutex_lock(&uuid_mutex);
> > +       btrfs_free_stale_devices(strlen(path) ? path:NULL, NULL);
>
> One space before : and another one after it please.
>
> Now the more important: don't use strlen, use strnlen. Some malicious
> or sloppy user might have passed a non-null terminated string, you
> don't want strlen to go past the limits of btrfs_ioctl_vol_args for
> obvious reasons.

In fact that's a problem for the entire use of vol->name in
btrfs_control_ioctl. The name's last byte should be set to '\0' to
avoid issues.
I'll send a fix for that, so if David fixes the white spaces on commit
there's no need for a v12.

>
> Also, please, not just to make a maintainer's life easier, but current
> and future reviewers, add the patch version to each patch's subject
> and not just the cover letter. Also list (after ---) what changes
> between each patch version in the patch itself and not the cover
> letter.
>
> V12, here we go.
>
> > +       mutex_unlock(&uuid_mutex);
> > +
> > +       return 0;
> > +}
> > +
> >  /*
> >   * Look for a btrfs signature on a device. This may be called out of the mount path
> >   * and we are not allowed to call set_blocksize during the scan. The superblock
> > diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> > index aefce895e994..180297d04938 100644
> > --- a/fs/btrfs/volumes.h
> > +++ b/fs/btrfs/volumes.h
> > @@ -406,6 +406,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
> >                        fmode_t flags, void *holder);
> >  struct btrfs_device *btrfs_scan_one_device(const char *path,
> >                                            fmode_t flags, void *holder);
> > +int btrfs_forget_devices(const char *path);
> >  int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
> >  void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
> >  void btrfs_assign_next_active_device(struct btrfs_device *device,
> > diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> > index 5ca1d21fc4a7..b1be7f828cb4 100644
> > --- a/include/uapi/linux/btrfs.h
> > +++ b/include/uapi/linux/btrfs.h
> > @@ -836,6 +836,8 @@ enum btrfs_err_code {
> >                                    struct btrfs_ioctl_vol_args)
> >  #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
> >                                    struct btrfs_ioctl_vol_args)
> > +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
> > +                                  struct btrfs_ioctl_vol_args)
> >  /* trans start and trans end are dangerous, and only for
> >   * use by applications that know how to avoid the
> >   * resulting deadlocks
> > --
> > 1.8.3.1
> >
>
>
> --
> Filipe David Manana,
>
> “Whether you think you can, or you think you can't — you're right.”



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

Re: [PATCH] btrfs: introduce feature to forget a btrfs device

[Anand Jain]

On 11/14/2018 07:15 PM, Filipe Manana wrote:
> On Wed, Nov 14, 2018 at 9:14 AM Anand Jain <anand.jain@oracle.com> wrote:
>>
>> Support for a new command 'btrfs dev forget [dev]' is proposed here
>> to undo the effects of 'btrfs dev scan [dev]'. For this purpose
>> this patch proposes to use ioctl #5 as it was empty.
>>          IOW(BTRFS_IOCTL_MAGIC, 5, ..)
>> This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
>> the /dev/btrfs-control to forget one or all devices, (devices which are
>> not mounted) from the btrfs kernel.
>>
>> The argument it takes is struct btrfs_ioctl_vol_args, and ::name can be
>> set to specify the device path. And all unmounted devices can be removed
>> from the kernel if no device path is provided.
>>
>> Again, the devices are removed only if the relevant fsid aren't mounted.
>>
>> This new cli can provide..
>>   . Release of unwanted btrfs_fs_devices and btrfs_devices memory if the
>>     device is not going to be mounted.
>>   . Ability to mount the device in degraded mode when one of the other
>>     device is corrupted like in split brain raid1.
>>   . Running test cases which requires btrfs.ko-reload if the rootfs
>>     is btrfs.
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
>> ---
>>   fs/btrfs/super.c           | 3 +++
>>   fs/btrfs/volumes.c         | 9 +++++++++
>>   fs/btrfs/volumes.h         | 1 +
>>   include/uapi/linux/btrfs.h | 2 ++
>>   4 files changed, 15 insertions(+)
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index 345c64d810d4..f99db6899004 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -2246,6 +2246,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>>                  ret = PTR_ERR_OR_ZERO(device);
>>                  mutex_unlock(&uuid_mutex);
>>                  break;
>> +       case BTRFS_IOC_FORGET_DEV:
>> +               ret = btrfs_forget_devices(vol->name);
>> +               break;
>>          case BTRFS_IOC_DEVICES_READY:
>>                  mutex_lock(&uuid_mutex);
>>                  device = btrfs_scan_one_device(vol->name, FMODE_READ,
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index f435d397019e..e1365a122657 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -1208,6 +1208,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>>          return 0;
>>   }
>>
>> +int btrfs_forget_devices(const char *path)
>> +{
>> +       mutex_lock(&uuid_mutex);
>> +       btrfs_free_stale_devices(strlen(path) ? path:NULL, NULL);
> 
> One space before : and another one after it please.

  will fix.

> Now the more important: don't use strlen, use strnlen. Some malicious
> or sloppy user might have passed a non-null terminated string, you
> don't want strlen to go past the limits of btrfs_ioctl_vol_args for
> obvious reasons.

  Makes sense. Will fix.

> Also, please, not just to make a maintainer's life easier, but current
> and future reviewers, add the patch version to each patch's subject
> and not just the cover letter. Also list (after ---) what changes
> between each patch version in the patch itself and not the cover
> letter.

  Sure. Thanks for the feedback.

-Anand

> V12, here we go.
> 
>> +       mutex_unlock(&uuid_mutex);
>> +
>> +       return 0;
>> +}
>> +
>>   /*
>>    * Look for a btrfs signature on a device. This may be called out of the mount path
>>    * and we are not allowed to call set_blocksize during the scan. The superblock
>> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>> index aefce895e994..180297d04938 100644
>> --- a/fs/btrfs/volumes.h
>> +++ b/fs/btrfs/volumes.h
>> @@ -406,6 +406,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>>                         fmode_t flags, void *holder);
>>   struct btrfs_device *btrfs_scan_one_device(const char *path,
>>                                             fmode_t flags, void *holder);
>> +int btrfs_forget_devices(const char *path);
>>   int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>>   void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>>   void btrfs_assign_next_active_device(struct btrfs_device *device,
>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>> index 5ca1d21fc4a7..b1be7f828cb4 100644
>> --- a/include/uapi/linux/btrfs.h
>> +++ b/include/uapi/linux/btrfs.h
>> @@ -836,6 +836,8 @@ enum btrfs_err_code {
>>                                     struct btrfs_ioctl_vol_args)
>>   #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
>>                                     struct btrfs_ioctl_vol_args)
>> +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
>> +                                  struct btrfs_ioctl_vol_args)
>>   /* trans start and trans end are dangerous, and only for
>>    * use by applications that know how to avoid the
>>    * resulting deadlocks
>> --
>> 1.8.3.1
>>
> 
> 

Re: [PATCH] btrfs: introduce feature to forget a btrfs device

[Anand Jain]

On 11/14/2018 07:28 PM, Filipe Manana wrote:
> On Wed, Nov 14, 2018 at 11:15 AM Filipe Manana <fdmanana@gmail.com> wrote:
>>
>> On Wed, Nov 14, 2018 at 9:14 AM Anand Jain <anand.jain@oracle.com> wrote:
>>>
>>> Support for a new command 'btrfs dev forget [dev]' is proposed here
>>> to undo the effects of 'btrfs dev scan [dev]'. For this purpose
>>> this patch proposes to use ioctl #5 as it was empty.
>>>          IOW(BTRFS_IOCTL_MAGIC, 5, ..)
>>> This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
>>> the /dev/btrfs-control to forget one or all devices, (devices which are
>>> not mounted) from the btrfs kernel.
>>>
>>> The argument it takes is struct btrfs_ioctl_vol_args, and ::name can be
>>> set to specify the device path. And all unmounted devices can be removed
>>> from the kernel if no device path is provided.
>>>
>>> Again, the devices are removed only if the relevant fsid aren't mounted.
>>>
>>> This new cli can provide..
>>>   . Release of unwanted btrfs_fs_devices and btrfs_devices memory if the
>>>     device is not going to be mounted.
>>>   . Ability to mount the device in degraded mode when one of the other
>>>     device is corrupted like in split brain raid1.
>>>   . Running test cases which requires btrfs.ko-reload if the rootfs
>>>     is btrfs.
>>>
>>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>>> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
>>> ---
>>>   fs/btrfs/super.c           | 3 +++
>>>   fs/btrfs/volumes.c         | 9 +++++++++
>>>   fs/btrfs/volumes.h         | 1 +
>>>   include/uapi/linux/btrfs.h | 2 ++
>>>   4 files changed, 15 insertions(+)
>>>
>>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>>> index 345c64d810d4..f99db6899004 100644
>>> --- a/fs/btrfs/super.c
>>> +++ b/fs/btrfs/super.c
>>> @@ -2246,6 +2246,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>>>                  ret = PTR_ERR_OR_ZERO(device);
>>>                  mutex_unlock(&uuid_mutex);
>>>                  break;
>>> +       case BTRFS_IOC_FORGET_DEV:
>>> +               ret = btrfs_forget_devices(vol->name);
>>> +               break;
>>>          case BTRFS_IOC_DEVICES_READY:
>>>                  mutex_lock(&uuid_mutex);
>>>                  device = btrfs_scan_one_device(vol->name, FMODE_READ,
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index f435d397019e..e1365a122657 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -1208,6 +1208,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>>>          return 0;
>>>   }
>>>
>>> +int btrfs_forget_devices(const char *path)
>>> +{
>>> +       mutex_lock(&uuid_mutex);
>>> +       btrfs_free_stale_devices(strlen(path) ? path:NULL, NULL);
>>
>> One space before : and another one after it please.
>>
>> Now the more important: don't use strlen, use strnlen. Some malicious
>> or sloppy user might have passed a non-null terminated string, you
>> don't want strlen to go past the limits of btrfs_ioctl_vol_args for
>> obvious reasons.
> 
> In fact that's a problem for the entire use of vol->name in
> btrfs_control_ioctl. The name's last byte should be set to '\0' to
> avoid issues.
> I'll send a fix for that, so if David fixes the white spaces on commit
> there's no need for a v12.

   Ok. Thanks.

   David, wonder if white spaces can be fixed when integrating?

Thanks, Anand

>>
>> Also, please, not just to make a maintainer's life easier, but current
>> and future reviewers, add the patch version to each patch's subject
>> and not just the cover letter. Also list (after ---) what changes
>> between each patch version in the patch itself and not the cover
>> letter.
>>
>> V12, here we go.
>>
>>> +       mutex_unlock(&uuid_mutex);
>>> +
>>> +       return 0;
>>> +}
>>> +
>>>   /*
>>>    * Look for a btrfs signature on a device. This may be called out of the mount path
>>>    * and we are not allowed to call set_blocksize during the scan. The superblock
>>> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>>> index aefce895e994..180297d04938 100644
>>> --- a/fs/btrfs/volumes.h
>>> +++ b/fs/btrfs/volumes.h
>>> @@ -406,6 +406,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>>>                         fmode_t flags, void *holder);
>>>   struct btrfs_device *btrfs_scan_one_device(const char *path,
>>>                                             fmode_t flags, void *holder);
>>> +int btrfs_forget_devices(const char *path);
>>>   int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>>>   void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>>>   void btrfs_assign_next_active_device(struct btrfs_device *device,
>>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>>> index 5ca1d21fc4a7..b1be7f828cb4 100644
>>> --- a/include/uapi/linux/btrfs.h
>>> +++ b/include/uapi/linux/btrfs.h
>>> @@ -836,6 +836,8 @@ enum btrfs_err_code {
>>>                                     struct btrfs_ioctl_vol_args)
>>>   #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
>>>                                     struct btrfs_ioctl_vol_args)
>>> +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
>>> +                                  struct btrfs_ioctl_vol_args)
>>>   /* trans start and trans end are dangerous, and only for
>>>    * use by applications that know how to avoid the
>>>    * resulting deadlocks
>>> --
>>> 1.8.3.1
>>>
>>
>>
>> --
>> Filipe David Manana,
>>
>> “Whether you think you can, or you think you can't — you're right.”
> 
> 
>