Hi Wang,
(2014/07/01 15:46), Wang Shilong wrote:
> Hi Satoru and all,
>
> I think there maybe a leftover issue.
> That is if we don't set label, in default it will output a blank line.
>
> Steps to reproduce:
>
> # mkfs.btrfs -f /dev/sdb
> # mount /dev/sdb
> # cat /sys/fs/btrfs/<uuid>/label -->an extra line will be outputed.
>
> This is because in btrfs_label_show(), we did something like this directly:
>
> return snprintf(buf, PAGE_SIZE, "%s\n", fs_info->super_copy->label);
>
> Maybe we can have a check whether label is NULL before we output?
> otherwise,the
> extra blank line is outputed, IMO this is not so nice thing!
OK, how about it is? I also add a test for empty-label case.
From: Anand Jain <Anand.Jain@xxxxxxxxxx>
generally if you use
echo "test" > /sys/fs/btrfs/<fsid>/label
it would introduce return char at the end and it can not
be part of the label. The correct command is
echo -n "test" > /sys/fs/btrfs/<fsid>/label
This patch will check for this user error
reproducer.sh:
===============================================================================
#!/bin/bash
TEST_DEV=/dev/vdb
TEST_DIR=/home/sat/mnt
umount /home/sat/mnt
mkfs.btrfs -f $TEST_DEV
UUID=$(btrfs fi show $TEST_DEV | head -1 | sed -e 's/.*uuid: \([-0-9a-z]*\)$/\1/')
mount $TEST_DEV $TEST_DIR
LABELFILE=/sys/fs/btrfs/$UUID/label
echo "Test for empty label..." >&2
LINES="$(cat $LABELFILE | wc -l | awk '{print $1}')"
RET=0
if [ $LINES -eq 0 ] ; then
echo '[PASS] Trailing \n is removed correctly.' >&2
else
echo '[FAIL] Trailing \n still exists.' >&2
RET=1
fi
echo "Test for non-empty label..." >&2
echo testlabel >$LABELFILE
LINES="$(cat $LABELFILE | wc -l | awk '{print $1}')"
if [ $LINES -eq 1 ] ; then
echo '[PASS] Trailing \n is removed correctly.' >&2
else
echo '[FAIL] Trailing \n still exists.' >&2
RET=1
fi
exit $RET
===============================================================================
Signed-off-by: Anand Jain <Anand.Jain@xxxxxxxxxx>
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Tested-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
---
v6: fix empty-label case
v5: tweak to be able to apply on the top of 402a0f4.
add test program.
v4: used memcpy and memset. Thanks David again
v3: accepts review comments. Thanks David and Eric again
v2: accepts review comments. Thanks Eric and Roman
---
fs/btrfs/sysfs.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index df39458..68d1f63 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -363,7 +363,8 @@ static ssize_t btrfs_label_show(struct kobject *kobj,
struct kobj_attribute *a, char *buf)
{
struct btrfs_fs_info *fs_info = to_fs_info(kobj);
- return snprintf(buf, PAGE_SIZE, "%s\n", fs_info->super_copy->label);
+ char *label = fs_info->super_copy->label;
+ return snprintf(buf, PAGE_SIZE, label[0] ? "%s\n" : "%s", label);
}
static ssize_t btrfs_label_store(struct kobject *kobj,
@@ -374,8 +375,15 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
struct btrfs_trans_handle *trans;
struct btrfs_root *root = fs_info->fs_root;
int ret;
+ size_t p_len;
- if (len >= BTRFS_LABEL_SIZE)
+ /*
+ * p_len is the len until the first occurrence of either
+ * '\n' or '\0'
+ */
+ p_len = strcspn(buf, "\n");
+
+ if (p_len >= BTRFS_LABEL_SIZE)
return -EINVAL;
trans = btrfs_start_transaction(root, 0);
@@ -383,7 +391,8 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
return PTR_ERR(trans);
spin_lock(&root->fs_info->super_lock);
- strcpy(fs_info->super_copy->label, buf);
+ memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
+ memcpy(fs_info->super_copy->label, buf, p_len);
spin_unlock(&root->fs_info->super_lock);
ret = btrfs_commit_transaction(trans, root);
--
1.9.3
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