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loop: Consolidate size calculation logic into lo_calculate_size() #135

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loop: Consolidate size calculation logic into lo_calculate_size() #135

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0bc715e
loop: Consolidate size calculation logic into lo_calculate_size()
Aug 18, 2025
a61d462
loop: use vfs_getattr_nosec for accurate file size
Aug 18, 2025
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39 changes: 21 additions & 18 deletions drivers/block/loop.c
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Original file line number Diff line number Diff line change
Expand Up @@ -137,32 +137,36 @@ 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)
{
struct kstat stat;
loff_t loopsize;
int ret;

/* Compute loopsize in bytes */
loopsize = i_size_read(file->f_mapping->host);
if (offset > 0)
loopsize -= offset;
/*
* 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 */
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.
*/
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
Expand Down Expand Up @@ -569,7 +573,7 @@ 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;

/*
Expand Down Expand Up @@ -1063,7 +1067,7 @@ 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(). */
Expand Down Expand Up @@ -1255,8 +1259,7 @@ 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:
Expand Down Expand Up @@ -1399,7 +1402,7 @@ 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;
Expand Down
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