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[PATCH v2] block: Use LVM tools for LV block device truncation

Alexander Ivanov posted 1 patch 1 month, 2 weeks ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20240313104327.147450-1-alexander.ivanov@virtuozzo.com
Maintainers: Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>
There is a newer version of this series
block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)
[PATCH v2] block: Use LVM tools for LV block device truncation
Posted by Alexander Ivanov 1 month, 2 weeks ago 
If a block device is an LVM logical volume we can resize it using
standard LVM tools.

Add a helper to detect if a device is a DM device. In raw_co_truncate()
check if the block device is DM and resize it executing lvresize.

Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
---
 block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/block/file-posix.c b/block/file-posix.c
index 35684f7e21..5f07d98aa5 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2642,6 +2642,38 @@ raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
     return raw_thread_pool_submit(handle_aiocb_truncate, &acb);
 }
 
+static bool device_is_dm(struct stat *st)
+{
+    unsigned int maj, maj2;
+    char line[32], devname[16];
+    bool ret = false;
+    FILE *f;
+
+    if (!S_ISBLK(st->st_mode)) {
+        return false;
+    }
+
+    f = fopen("/proc/devices", "r");
+    if (!f) {
+        return false;
+    }
+
+    maj = major(st->st_rdev);
+
+    while (fgets(line, sizeof(line), f)) {
+        if (sscanf(line, "%u %15s", &maj2, devname) != 2) {
+            continue;
+        }
+        if (strcmp(devname, "device-mapper") == 0) {
+            ret = (maj == maj2);
+            break;
+        }
+    }
+
+    fclose(f);
+    return ret;
+}
+
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
                                         BdrvRequestFlags flags, Error **errp)
@@ -2670,6 +2702,35 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
     if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
         int64_t cur_length = raw_getlength(bs);
 
+        /*
+         * Try to resize an LVM device using LVM tools.
+         */
+        if (device_is_dm(&st) && offset > 0) {
+            int spawn_flags = G_SPAWN_SEARCH_PATH | G_SPAWN_STDOUT_TO_DEV_NULL;
+            int status;
+            bool success;
+            char *err;
+            GError *gerr = NULL;
+            g_autofree char *size_str = g_strdup_printf("%ldB", offset);
+            const char *cmd[] = {"lvresize", "-f", "-L",
+                                 size_str, bs->filename, NULL};
+
+            success = g_spawn_sync(NULL, (gchar **)cmd, NULL, spawn_flags,
+                                   NULL, NULL, NULL, &err, &status, &gerr);
+
+            if (success && WEXITSTATUS(status) == 0) {
+                return 0;
+            }
+
+            if (!success) {
+                error_setg(errp, "lvresize execution error: %s", gerr->message);
+            } else {
+                error_setg(errp, "%s", err);
+            }
+
+            return -EINVAL;
+        }
+
         if (offset != cur_length && exact) {
             error_setg(errp, "Cannot resize device files");
             return -ENOTSUP;
-- 
2.40.1
Re: [PATCH v2] block: Use LVM tools for LV block device truncation
Posted by Daniel P. Berrangé 1 month, 2 weeks ago 
On Wed, Mar 13, 2024 at 11:43:27AM +0100, Alexander Ivanov wrote:
> If a block device is an LVM logical volume we can resize it using
> standard LVM tools.
> 
> Add a helper to detect if a device is a DM device. In raw_co_truncate()
> check if the block device is DM and resize it executing lvresize.
> 
> Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> ---
>  block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 35684f7e21..5f07d98aa5 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -2642,6 +2642,38 @@ raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
>      return raw_thread_pool_submit(handle_aiocb_truncate, &acb);
>  }

>  static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>                                          bool exact, PreallocMode prealloc,
>                                          BdrvRequestFlags flags, Error **errp)
> @@ -2670,6 +2702,35 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>      if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
>          int64_t cur_length = raw_getlength(bs);
>  
> +        /*
> +         * Try to resize an LVM device using LVM tools.
> +         */
> +        if (device_is_dm(&st) && offset > 0) {
> +            int spawn_flags = G_SPAWN_SEARCH_PATH | G_SPAWN_STDOUT_TO_DEV_NULL;
> +            int status;
> +            bool success;
> +            char *err;
> +            GError *gerr = NULL;
> +            g_autofree char *size_str = g_strdup_printf("%ldB", offset);

offset is 64-bit, but '%ld' is not guaranteed to be 64-bit. I expect
this will break on 32-bit platforms. Try PRId64 instead.

> +            const char *cmd[] = {"lvresize", "-f", "-L",
> +                                 size_str, bs->filename, NULL};
> +
> +            success = g_spawn_sync(NULL, (gchar **)cmd, NULL, spawn_flags,
> +                                   NULL, NULL, NULL, &err, &status, &gerr);
> +
> +            if (success && WEXITSTATUS(status) == 0) {
> +                return 0;
> +            }

We should probably check  'g_spawn_check_wait_status' rather than
WEXITSTATUS, as this then gives us further eror message details
that....

> +
> +            if (!success) {
> +                error_setg(errp, "lvresize execution error: %s", gerr->message);
> +            } else {
> +                error_setg(errp, "%s", err);

...we would also include here, such as the exit code or terminal
signal.

> +            }
> +
> +            return -EINVAL;
> +        }
> +
>          if (offset != cur_length && exact) {
>              error_setg(errp, "Cannot resize device files");
>              return -ENOTSUP;
> -- 
> 2.40.1
> 
> 

With regards,
Daniel
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Re: [PATCH v2] block: Use LVM tools for LV block device truncation
Posted by Alexander Ivanov 1 month, 2 weeks ago 

On 3/14/24 13:44, Daniel P. Berrangé wrote:
> On Wed, Mar 13, 2024 at 11:43:27AM +0100, Alexander Ivanov wrote:
>> If a block device is an LVM logical volume we can resize it using
>> standard LVM tools.
>>
>> Add a helper to detect if a device is a DM device. In raw_co_truncate()
>> check if the block device is DM and resize it executing lvresize.
>>
>> Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
>> ---
>>   block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 61 insertions(+)
>>
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index 35684f7e21..5f07d98aa5 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -2642,6 +2642,38 @@ raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
>>       return raw_thread_pool_submit(handle_aiocb_truncate, &acb);
>>   }
>>   static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>>                                           bool exact, PreallocMode prealloc,
>>                                           BdrvRequestFlags flags, Error **errp)
>> @@ -2670,6 +2702,35 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>>       if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
>>           int64_t cur_length = raw_getlength(bs);
>>   
>> +        /*
>> +         * Try to resize an LVM device using LVM tools.
>> +         */
>> +        if (device_is_dm(&st) && offset > 0) {
>> +            int spawn_flags = G_SPAWN_SEARCH_PATH | G_SPAWN_STDOUT_TO_DEV_NULL;
>> +            int status;
>> +            bool success;
>> +            char *err;
>> +            GError *gerr = NULL;
>> +            g_autofree char *size_str = g_strdup_printf("%ldB", offset);
> offset is 64-bit, but '%ld' is not guaranteed to be 64-bit. I expect
> this will break on 32-bit platforms. Try PRId64 instead.
>
>> +            const char *cmd[] = {"lvresize", "-f", "-L",
>> +                                 size_str, bs->filename, NULL};
>> +
>> +            success = g_spawn_sync(NULL, (gchar **)cmd, NULL, spawn_flags,
>> +                                   NULL, NULL, NULL, &err, &status, &gerr);
>> +
>> +            if (success && WEXITSTATUS(status) == 0) {
>> +                return 0;
>> +            }
> We should probably check  'g_spawn_check_wait_status' rather than
> WEXITSTATUS, as this then gives us further eror message details
> that....
Thank you.
I think it would be better to use 'g_spawn_check_exit_status' because 
there is no
'g_spawn_check_wait_status' in glib before 2.70 and even in 2.78 it 
leads to
'g_spawn_check_wait_status is deprecated: Not available before 2.70' error.
>
>> +
>> +            if (!success) {
>> +                error_setg(errp, "lvresize execution error: %s", gerr->message);
>> +            } else {
>> +                error_setg(errp, "%s", err);
> ...we would also include here, such as the exit code or terminal
> signal.
>
>> +            }
>> +
>> +            return -EINVAL;
>> +        }
>> +
>>           if (offset != cur_length && exact) {
>>               error_setg(errp, "Cannot resize device files");
>>               return -ENOTSUP;
>> -- 
>> 2.40.1
>>
>>
> With regards,
> Daniel

-- 
Best regards,
Alexander Ivanov
Re: [PATCH v2] block: Use LVM tools for LV block device truncation
Posted by Daniel P. Berrangé 1 month, 2 weeks ago 
On Thu, Mar 14, 2024 at 06:25:00PM +0100, Alexander Ivanov wrote:
> 
> 
> On 3/14/24 13:44, Daniel P. Berrangé wrote:
> > On Wed, Mar 13, 2024 at 11:43:27AM +0100, Alexander Ivanov wrote:
> > > If a block device is an LVM logical volume we can resize it using
> > > standard LVM tools.
> > > 
> > > Add a helper to detect if a device is a DM device. In raw_co_truncate()
> > > check if the block device is DM and resize it executing lvresize.
> > > 
> > > Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> > > ---
> > >   block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 61 insertions(+)
> > > 
> > > diff --git a/block/file-posix.c b/block/file-posix.c
> > > index 35684f7e21..5f07d98aa5 100644
> > > --- a/block/file-posix.c
> > > +++ b/block/file-posix.c
> > > @@ -2642,6 +2642,38 @@ raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
> > >       return raw_thread_pool_submit(handle_aiocb_truncate, &acb);
> > >   }
> > >   static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
> > >                                           bool exact, PreallocMode prealloc,
> > >                                           BdrvRequestFlags flags, Error **errp)
> > > @@ -2670,6 +2702,35 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
> > >       if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
> > >           int64_t cur_length = raw_getlength(bs);
> > > +        /*
> > > +         * Try to resize an LVM device using LVM tools.
> > > +         */
> > > +        if (device_is_dm(&st) && offset > 0) {
> > > +            int spawn_flags = G_SPAWN_SEARCH_PATH | G_SPAWN_STDOUT_TO_DEV_NULL;
> > > +            int status;
> > > +            bool success;
> > > +            char *err;
> > > +            GError *gerr = NULL;
> > > +            g_autofree char *size_str = g_strdup_printf("%ldB", offset);
> > offset is 64-bit, but '%ld' is not guaranteed to be 64-bit. I expect
> > this will break on 32-bit platforms. Try PRId64 instead.
> > 
> > > +            const char *cmd[] = {"lvresize", "-f", "-L",
> > > +                                 size_str, bs->filename, NULL};
> > > +
> > > +            success = g_spawn_sync(NULL, (gchar **)cmd, NULL, spawn_flags,
> > > +                                   NULL, NULL, NULL, &err, &status, &gerr);
> > > +
> > > +            if (success && WEXITSTATUS(status) == 0) {
> > > +                return 0;
> > > +            }
> > We should probably check  'g_spawn_check_wait_status' rather than
> > WEXITSTATUS, as this then gives us further eror message details
> > that....
> Thank you.
> I think it would be better to use 'g_spawn_check_exit_status' because there
> is no
> 'g_spawn_check_wait_status' in glib before 2.70 and even in 2.78 it leads to
> 'g_spawn_check_wait_status is deprecated: Not available before 2.70' error.

Ah yes, well spotted.


With regards,
Daniel
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