Hi,
在 2025/08/13 4:07, Rajeev Mishra 写道:
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.
Signed-off-by: Rajeev Mishra <rajeevm@xxxxxxx>
---
drivers/block/loop.c | 53 +++++++++++++++++++++++++++++---------------
1 file changed, 35 insertions(+), 18 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 1b6ee91f8eb9..6bfec38275b0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -137,20 +137,43 @@ 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)
+/**
+ * lo_calculate_size - calculate the effective size of a loop device
+ * @lo: loop device
+ * @file: backing file
+ *
+ * Calculate the effective size of the loop device based on backing file size,
+ * offset, and size limit. Uses vfs_getattr_nosec() for accurate file size
+ * information, particularly important for network filesystems where cached
+ * metadata may be stale.
+ *
+ * Returns: size in 512-byte sectors, or 0 on error
+ */
I feel this internal function comment is not necessary, the name can
explain itself, and you explain getattr below as well.
Otherwise this patch LGTM.
Thanks,
Kuai
+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;
- /* offset is beyond i_size, weird but possible */
+ /*
+ * 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 file 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 +181,6 @@ 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 +587,7 @@ 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 +1081,7 @@ 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 +1273,7 @@ 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 +1416,7 @@ 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;
