[PATCH v4 0/2] review of v3 loop: use vfs_getattr_nosec()

[PATCH v4 0/2] review of v3 loop: use vfs_getattr_nosec()

[Rajeev Mishra]

> This commit includes the following changes:
>   1. Renamed get_size to lo_calculate_size.
>   2. Merged the functionality of get_size and
>      get_loop_size into lo_calculate_size.
>   3  Updated callers of the above functions
>      to use lo_calculate_size.
>   4. Replaced i_size_read with vfs_getattr_nosec()
>      to obtain a more accurate file size for
>       network filesystems where cached metadata may be stale
>
Please split 1-3 to a seperate patch.
removed header also

Rajeev Mishra (2):
  loop: Rename and merge get_size/get_loop_size to lo_calculate_size
  loop: use vfs_getattr_nosec for accurate file size

 drivers/block/loop.c | 61 +++++++++++++++++++++++---------------------
 1 file changed, 32 insertions(+), 29 deletions(-)

-- 
2.43.7

[PATCH v4 1/2] loop: Rename and merge get_size/get_loop_size to lo_calculate_size

[Rajeev Mishra]

- Renamed get_size to lo_calculate_size.
- Merged get_size and get_loop_size logic into lo_calculate_size.
- Updated all callers to use lo_calculate_size.
- Added header to lo_calculate_size.

Signed-off-by: Rajeev Mishra <rajeevm@hpe.com>
---
 drivers/block/loop.c | 50 +++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 29 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 1b6ee91f8eb9..5faf8607dfb2 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -137,30 +137,23 @@ static void loop_global_unlock(struct loop_device *lo, bool global)
 static int max_part;
 static int part_shift;
 
-static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
-{
-	loff_t loopsize;
-
-	/* Compute loopsize in bytes */
-	loopsize = i_size_read(file->f_mapping->host);
-	if (offset > 0)
-		loopsize -= offset;
-	/* offset is beyond i_size, weird but possible */
-	if (loopsize < 0)
-		return 0;
-
-	if (sizelimit > 0 && sizelimit < loopsize)
-		loopsize = sizelimit;
-	/*
-	 * Unfortunately, if we want to do I/O on the device,
-	 * the number of 512-byte sectors has to fit into a sector_t.
-	 */
-	return loopsize >> 9;
-}
-
-static loff_t get_loop_size(struct loop_device *lo, struct file *file)
-{
-	return get_size(lo->lo_offset, lo->lo_sizelimit, file);
+static loff_t lo_calculate_size(struct loop_device *lo, struct file *file)
+{
+       loff_t loopsize;
+       /* Compute loopsize in bytes */
+       loopsize = i_size_read(file->f_mapping->host);
+       if (lo->lo_offset > 0)
+	       loopsize -= lo->lo_offset;
+       /* offset is beyond i_size, weird but possible */
+       if (loopsize < 0)
+	       return 0;
+       if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
+	       loopsize = lo->lo_sizelimit;
+       /*
+	* Unfortunately, if we want to do I/O on the device,
+	* the number of 512-byte sectors has to fit into a sector_t.
+	*/
+       return loopsize >> 9;
 }
 
 /*
@@ -569,7 +562,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	error = -EINVAL;
 
 	/* size of the new backing store needs to be the same */
-	if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
+	if (lo_calculate_size(lo, file) != lo_calculate_size(lo, old_file))
 		goto out_err;
 
 	/*
@@ -1063,7 +1056,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	loop_update_dio(lo);
 	loop_sysfs_init(lo);
 
-	size = get_loop_size(lo, file);
+	size = lo_calculate_size(lo, file);
 	loop_set_size(lo, size);
 
 	/* Order wrt reading lo_state in loop_validate_file(). */
@@ -1255,8 +1248,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 	if (partscan)
 		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
 	if (!err && size_changed) {
-		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
-					   lo->lo_backing_file);
+		loff_t new_size = lo_calculate_size(lo, lo->lo_backing_file);
 		loop_set_size(lo, new_size);
 	}
 out_unlock:
@@ -1399,7 +1391,7 @@ static int loop_set_capacity(struct loop_device *lo)
 	if (unlikely(lo->lo_state != Lo_bound))
 		return -ENXIO;
 
-	size = get_loop_size(lo, lo->lo_backing_file);
+	size = lo_calculate_size(lo, lo->lo_backing_file);
 	loop_set_size(lo, size);
 
 	return 0;
-- 
2.43.7

[PATCH v4 2/2] loop: use vfs_getattr_nosec for accurate file size

[Rajeev Mishra]

- Use vfs_getattr_nosec() instead of i_size_read() in lo_calculate_size.
- Improves accuracy for network/distributed filesystems.

Signed-off-by: Rajeev Mishra <rajeevm@hpe.com>
---
 drivers/block/loop.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5faf8607dfb2..0a2703eda2c2 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -139,9 +139,20 @@ static int part_shift;
 
 static loff_t lo_calculate_size(struct loop_device *lo, struct file *file)
 {
+       struct kstat stat;
        loff_t loopsize;
-       /* Compute loopsize in bytes */
-       loopsize = i_size_read(file->f_mapping->host);
+       int ret;
+
+       /*
+	* Get the accurate file size. This provides better results than
+	* cached inode data, particularly for network filesystems where
+	* metadata may be stale.
+	*/
+       ret = vfs_getattr_nosec(&file->f_path, &stat, STATX_SIZE, 0);
+       if (ret)
+	       return 0;
+
+       loopsize = stat.size;
        if (lo->lo_offset > 0)
 	       loopsize -= lo->lo_offset;
        /* offset is beyond i_size, weird but possible */
-- 
2.43.7

Re: [PATCH v4 1/2] loop: Rename and merge get_size/get_loop_size to lo_calculate_size

[Yu Kuai]

Hi,

在 2025/08/14 3:52, Rajeev Mishra 写道:
> - Renamed get_size to lo_calculate_size.
> - Merged get_size and get_loop_size logic into lo_calculate_size.
> - Updated all callers to use lo_calculate_size.
> - Added header to lo_calculate_size.
> 
> Signed-off-by: Rajeev Mishra <rajeevm@hpe.com>
> ---
>   drivers/block/loop.c | 50 +++++++++++++++++++-------------------------
>   1 file changed, 21 insertions(+), 29 deletions(-)
> 

This patch has lots of style issues, please run checkpatch and fix
the warnings first.

Thanks,
Kuai

./scripts/checkpatch.pl 
0001-loop-Rename-and-merge-get_size-get_loop_size-to-lo_c.patch
WARNING: please, no spaces at the start of a line
#52: FILE: drivers/block/loop.c:142:
+       loff_t loopsize;$

WARNING: please, no spaces at the start of a line
#54: FILE: drivers/block/loop.c:144:
+       loopsize = i_size_read(file->f_mapping->host);$

WARNING: please, no spaces at the start of a line
#55: FILE: drivers/block/loop.c:145:
+       if (lo->lo_offset > 0)$

WARNING: suspect code indent for conditional statements (7, 15)
#55: FILE: drivers/block/loop.c:145:
+       if (lo->lo_offset > 0)
+              loopsize -= lo->lo_offset;

WARNING: please, no spaces at the start of a line
#58: FILE: drivers/block/loop.c:148:
+       if (loopsize < 0)$

WARNING: suspect code indent for conditional statements (7, 15)
#58: FILE: drivers/block/loop.c:148:
+       if (loopsize < 0)
+              return 0;

WARNING: Statements should start on a tabstop
#59: FILE: drivers/block/loop.c:149:
+              return 0;

WARNING: please, no spaces at the start of a line
#60: FILE: drivers/block/loop.c:150:
+       if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)$

WARNING: suspect code indent for conditional statements (7, 15)
#60: FILE: drivers/block/loop.c:150:
+       if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
+              loopsize = lo->lo_sizelimit;

WARNING: please, no spaces at the start of a line
#66: FILE: drivers/block/loop.c:156:
+       return loopsize >> 9;$

total: 0 errors, 10 warnings, 80 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
       mechanically convert to the typical style using --fix or 
--fix-inplace.

0001-loop-Rename-and-merge-get_size-get_loop_size-to-lo_c.patch has 
style problems, please review.

NOTE: If any of the errors are false positives, please report
       them to the maintainer, see CHECKPATCH in MAINTAINERS.

> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 1b6ee91f8eb9..5faf8607dfb2 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -137,30 +137,23 @@ static void loop_global_unlock(struct loop_device *lo, bool global)
>   static int max_part;
>   static int part_shift;
>   
> -static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
> -{
> -	loff_t loopsize;
> -
> -	/* Compute loopsize in bytes */
> -	loopsize = i_size_read(file->f_mapping->host);
> -	if (offset > 0)
> -		loopsize -= offset;
> -	/* offset is beyond i_size, weird but possible */
> -	if (loopsize < 0)
> -		return 0;
> -
> -	if (sizelimit > 0 && sizelimit < loopsize)
> -		loopsize = sizelimit;
> -	/*
> -	 * Unfortunately, if we want to do I/O on the device,
> -	 * the number of 512-byte sectors has to fit into a sector_t.
> -	 */
> -	return loopsize >> 9;
> -}
> -
> -static loff_t get_loop_size(struct loop_device *lo, struct file *file)
> -{
> -	return get_size(lo->lo_offset, lo->lo_sizelimit, file);
> +static loff_t lo_calculate_size(struct loop_device *lo, struct file *file)
> +{
> +       loff_t loopsize;
> +       /* Compute loopsize in bytes */
> +       loopsize = i_size_read(file->f_mapping->host);
> +       if (lo->lo_offset > 0)
> +	       loopsize -= lo->lo_offset;
> +       /* offset is beyond i_size, weird but possible */
> +       if (loopsize < 0)
> +	       return 0;
> +       if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
> +	       loopsize = lo->lo_sizelimit;
> +       /*
> +	* Unfortunately, if we want to do I/O on the device,
> +	* the number of 512-byte sectors has to fit into a sector_t.
> +	*/
> +       return loopsize >> 9;
>   }
>   
>   /*
> @@ -569,7 +562,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
>   	error = -EINVAL;
>   
>   	/* size of the new backing store needs to be the same */
> -	if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
> +	if (lo_calculate_size(lo, file) != lo_calculate_size(lo, old_file))
>   		goto out_err;
>   
>   	/*
> @@ -1063,7 +1056,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
>   	loop_update_dio(lo);
>   	loop_sysfs_init(lo);
>   
> -	size = get_loop_size(lo, file);
> +	size = lo_calculate_size(lo, file);
>   	loop_set_size(lo, size);
>   
>   	/* Order wrt reading lo_state in loop_validate_file(). */
> @@ -1255,8 +1248,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
>   	if (partscan)
>   		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
>   	if (!err && size_changed) {
> -		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
> -					   lo->lo_backing_file);
> +		loff_t new_size = lo_calculate_size(lo, lo->lo_backing_file);
>   		loop_set_size(lo, new_size);
>   	}
>   out_unlock:
> @@ -1399,7 +1391,7 @@ static int loop_set_capacity(struct loop_device *lo)
>   	if (unlikely(lo->lo_state != Lo_bound))
>   		return -ENXIO;
>   
> -	size = get_loop_size(lo, lo->lo_backing_file);
> +	size = lo_calculate_size(lo, lo->lo_backing_file);
>   	loop_set_size(lo, size);
>   
>   	return 0;
> 

Re: [PATCH v4 1/2] loop: Rename and merge get_size/get_loop_size to lo_calculate_size

[Jens Axboe]

On 8/14/25 1:10 PM, Rajeev Mishra wrote:
> - Renamed get_size to lo_calculate_size.
> - Merged get_size and get_loop_size logic into lo_calculate_size.
> - Updated all callers to use lo_calculate_size.
> - Added header to lo_calculate_size.

Please write a proper commit message, rather than these itemized
lists. Goes for both patches.

-- 
Jens Axboe

Re: [PATCH v4 1/2] loop: Rename and merge get_size/get_loop_size to lo_calculate_size

[Yu Kuai]

在 2025/08/15 3:10, Rajeev Mishra 写道:
> - Renamed get_size to lo_calculate_size.
> - Merged get_size and get_loop_size logic into lo_calculate_size.
> - Updated all callers to use lo_calculate_size.
> - Added header to lo_calculate_size.
> 
> Signed-off-by: Rajeev Mishra<rajeevm@hpe.com>
> ---
>   drivers/block/loop.c | 26 +++++++++-----------------
>   1 file changed, 9 insertions(+), 17 deletions(-)

LGTM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>

[PATCH v4 1/2] loop: Rename and merge get_size/get_loop_size to lo_calculate_size

[Rajeev Mishra]

- Renamed get_size to lo_calculate_size.
- Merged get_size and get_loop_size logic into lo_calculate_size.
- Updated all callers to use lo_calculate_size.
- Added header to lo_calculate_size.

Signed-off-by: Rajeev Mishra <rajeevm@hpe.com>
---
 drivers/block/loop.c | 26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 1b6ee91f8eb9..0e1b9eb9db10 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -137,20 +137,18 @@ static void loop_global_unlock(struct loop_device *lo, bool global)
 static int max_part;
 static int part_shift;
 
-static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
+static loff_t lo_calculate_size(struct loop_device *lo, struct file *file)
 {
 	loff_t loopsize;
-
 	/* Compute loopsize in bytes */
 	loopsize = i_size_read(file->f_mapping->host);
-	if (offset > 0)
-		loopsize -= offset;
+	if (lo->lo_offset > 0)
+		loopsize -= lo->lo_offset;
 	/* offset is beyond i_size, weird but possible */
 	if (loopsize < 0)
 		return 0;
-
-	if (sizelimit > 0 && sizelimit < loopsize)
-		loopsize = sizelimit;
+	if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
+		loopsize = lo->lo_sizelimit;
 	/*
 	 * Unfortunately, if we want to do I/O on the device,
 	 * the number of 512-byte sectors has to fit into a sector_t.
@@ -158,11 +156,6 @@ static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
 	return loopsize >> 9;
 }
 
-static loff_t get_loop_size(struct loop_device *lo, struct file *file)
-{
-	return get_size(lo->lo_offset, lo->lo_sizelimit, file);
-}
-
 /*
  * We support direct I/O only if lo_offset is aligned with the logical I/O size
  * of backing device, and the logical block size of loop is bigger than that of
@@ -569,7 +562,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	error = -EINVAL;
 
 	/* size of the new backing store needs to be the same */
-	if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
+	if (lo_calculate_size(lo, file) != lo_calculate_size(lo, old_file))
 		goto out_err;
 
 	/*
@@ -1063,7 +1056,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	loop_update_dio(lo);
 	loop_sysfs_init(lo);
 
-	size = get_loop_size(lo, file);
+	size = lo_calculate_size(lo, file);
 	loop_set_size(lo, size);
 
 	/* Order wrt reading lo_state in loop_validate_file(). */
@@ -1255,8 +1248,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 	if (partscan)
 		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
 	if (!err && size_changed) {
-		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
-					   lo->lo_backing_file);
+		loff_t new_size = lo_calculate_size(lo, lo->lo_backing_file);
 		loop_set_size(lo, new_size);
 	}
 out_unlock:
@@ -1399,7 +1391,7 @@ static int loop_set_capacity(struct loop_device *lo)
 	if (unlikely(lo->lo_state != Lo_bound))
 		return -ENXIO;
 
-	size = get_loop_size(lo, lo->lo_backing_file);
+	size = lo_calculate_size(lo, lo->lo_backing_file);
 	loop_set_size(lo, size);
 
 	return 0;
-- 
2.43.7