diff mbox series

tst_find_backing_dev: fix logic in matching mount point

Message ID b30a6712179ead9c8a5556d82a4ac386904c9b4d.1657265564.git.jstancek@redhat.com
State New
Headers show
Series tst_find_backing_dev: fix logic in matching mount point | expand

Commit Message

Jan Stancek July 8, 2022, 7:33 a.m. UTC
If backing dev is btrfs root device, then starting best_match_len
from 1 creates an issue, because root (/) is never matched.
Also we should check that entire mount point string is present in
path we are matching against.

In case there's error also dump /proc/self/mountinfo before tst_brk.

This fixes test with following partition layout (TMPDIR is on /):
  # cat /proc/self/mountinfo  | grep btrfs
  59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
  93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 lib/tst_device.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

Comments

Li Wang July 11, 2022, 6:52 a.m. UTC | #1
On Fri, Jul 8, 2022 at 3:33 PM Jan Stancek <jstancek@redhat.com> wrote:

> If backing dev is btrfs root device, then starting best_match_len
> from 1 creates an issue, because root (/) is never matched.
> Also we should check that entire mount point string is present in
> path we are matching against.
>
> In case there's error also dump /proc/self/mountinfo before tst_brk.
>
> This fixes test with following partition layout (TMPDIR is on /):
>   # cat /proc/self/mountinfo  | grep btrfs
>   59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2
> rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
>   93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2
> rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home
>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
>

Make sense!

Reviewed-by: Li Wang <liwang@redhat.com>
Richard Palethorpe July 11, 2022, 12:05 p.m. UTC | #2
Hello,

Jan Stancek <jstancek@redhat.com> writes:

> If backing dev is btrfs root device, then starting best_match_len
> from 1 creates an issue, because root (/) is never matched.
> Also we should check that entire mount point string is present in
> path we are matching against.
>
> In case there's error also dump /proc/self/mountinfo before tst_brk.
>
> This fixes test with following partition layout (TMPDIR is on /):
>   # cat /proc/self/mountinfo  | grep btrfs
>   59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
>   93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home
>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---
>  lib/tst_device.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/lib/tst_device.c b/lib/tst_device.c
> index c34cbe6d1f56..414bf0eea816 100644
> --- a/lib/tst_device.c
> +++ b/lib/tst_device.c
> @@ -506,12 +506,17 @@ unsigned long tst_dev_bytes_written(const char *dev)
>  	return dev_bytes_written;
>  }
>  
> -static int count_match_len(const char *first, const char *second)
> +static int str_starts_with(const char *str, const char *prefix)
>  {
>  	int len = 0;
>  
> -	while (*first && *first++ == *second++)
> +	while (*prefix) {
> +		if (!*str)
> +			return 0;
> +		if (*str++ != *prefix++)
> +			return 0;
>  		len++;
> +	}

I'm not sure this is better than the original. It's a seperate cleanup
in any case.

>  
>  	return len;
>  }
> @@ -524,7 +529,7 @@ void tst_find_backing_dev(const char *path, char *dev)
>  	char *pre = NULL;
>  	char *next = NULL;
>  	unsigned int dev_major, dev_minor, line_mjr, line_mnr;
> -	unsigned int len, best_match_len = 1;
> +	unsigned int len, best_match_len = 0;
>  	char mnt_point[PATH_MAX];
>  
>  	if (stat(path, &buf) < 0)
> @@ -550,7 +555,7 @@ void tst_find_backing_dev(const char *path, char *dev)
>  			break;
>  		}
>  
> -		len = count_match_len(path, mnt_point);
> +		len = str_starts_with(path, mnt_point);
>  		if (len > best_match_len) {
>  			strcpy(dev, pre);
>  			best_match_len = len;
> @@ -559,8 +564,10 @@ void tst_find_backing_dev(const char *path, char *dev)
>  
>  	SAFE_FCLOSE(NULL, file);
>  
> -	if (!*dev)
> +	if (!*dev) {
> +		tst_system("cat /proc/self/mountinfo");
>  		tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
> +	}
>  
>  	if (stat(dev, &buf) < 0)
>  		tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
> -- 
> 2.27.0

Makes sense. However I suspect this function can be replaced with the
standard library method used in tst_stat_mount_dev. I didn't try this
before because I'm not sure why it scans mountinfo instead of mounts.
Jan Stancek July 11, 2022, 1:04 p.m. UTC | #3
On Mon, Jul 11, 2022 at 2:13 PM Richard Palethorpe <rpalethorpe@suse.de> wrote:
>
> Hello,
>
> Jan Stancek <jstancek@redhat.com> writes:
>
> > If backing dev is btrfs root device, then starting best_match_len
> > from 1 creates an issue, because root (/) is never matched.
> > Also we should check that entire mount point string is present in
> > path we are matching against.
> >
> > In case there's error also dump /proc/self/mountinfo before tst_brk.
> >
> > This fixes test with following partition layout (TMPDIR is on /):
> >   # cat /proc/self/mountinfo  | grep btrfs
> >   59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
> >   93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home
> >
> > Signed-off-by: Jan Stancek <jstancek@redhat.com>
> > ---
> >  lib/tst_device.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/tst_device.c b/lib/tst_device.c
> > index c34cbe6d1f56..414bf0eea816 100644
> > --- a/lib/tst_device.c
> > +++ b/lib/tst_device.c
> > @@ -506,12 +506,17 @@ unsigned long tst_dev_bytes_written(const char *dev)
> >       return dev_bytes_written;
> >  }
> >
> > -static int count_match_len(const char *first, const char *second)
> > +static int str_starts_with(const char *str, const char *prefix)
> >  {
> >       int len = 0;
> >
> > -     while (*first && *first++ == *second++)
> > +     while (*prefix) {
> > +             if (!*str)
> > +                     return 0;
> > +             if (*str++ != *prefix++)
> > +                     return 0;
> >               len++;
> > +     }
>
> I'm not sure this is better than the original. It's a seperate cleanup
> in any case.

The difference is that partial matches now returns 0. Previously it did not,
it only counted number of matching characters. So for example ("/foobar" "/foo")
appeared as better match than ("/foobar", "/")

>
> >
> >       return len;
> >  }
> > @@ -524,7 +529,7 @@ void tst_find_backing_dev(const char *path, char *dev)
> >       char *pre = NULL;
> >       char *next = NULL;
> >       unsigned int dev_major, dev_minor, line_mjr, line_mnr;
> > -     unsigned int len, best_match_len = 1;
> > +     unsigned int len, best_match_len = 0;
> >       char mnt_point[PATH_MAX];
> >
> >       if (stat(path, &buf) < 0)
> > @@ -550,7 +555,7 @@ void tst_find_backing_dev(const char *path, char *dev)
> >                       break;
> >               }
> >
> > -             len = count_match_len(path, mnt_point);
> > +             len = str_starts_with(path, mnt_point);
> >               if (len > best_match_len) {
> >                       strcpy(dev, pre);
> >                       best_match_len = len;
> > @@ -559,8 +564,10 @@ void tst_find_backing_dev(const char *path, char *dev)
> >
> >       SAFE_FCLOSE(NULL, file);
> >
> > -     if (!*dev)
> > +     if (!*dev) {
> > +             tst_system("cat /proc/self/mountinfo");
> >               tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
> > +     }
> >
> >       if (stat(dev, &buf) < 0)
> >               tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
> > --
> > 2.27.0
>
> Makes sense. However I suspect this function can be replaced with the
> standard library method used in tst_stat_mount_dev. I didn't try this
> before because I'm not sure why it scans mountinfo instead of mounts.

/proc/self/mounts doesn't contain major/minor numbers, which is primarily what
tst_find_backing_dev is using.

>
>
> --
> Thank you,
> Richard.
>
Richard Palethorpe July 11, 2022, 1:11 p.m. UTC | #4
Hello,

Jan Stancek <jstancek@redhat.com> writes:

> On Mon, Jul 11, 2022 at 2:13 PM Richard Palethorpe <rpalethorpe@suse.de> wrote:
>>
>> Hello,
>>
>> Jan Stancek <jstancek@redhat.com> writes:
>>
>> > If backing dev is btrfs root device, then starting best_match_len
>> > from 1 creates an issue, because root (/) is never matched.
>> > Also we should check that entire mount point string is present in
>> > path we are matching against.
>> >
>> > In case there's error also dump /proc/self/mountinfo before tst_brk.
>> >
>> > This fixes test with following partition layout (TMPDIR is on /):
>> >   # cat /proc/self/mountinfo  | grep btrfs
>> >   59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
>> >   93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home
>> >
>> > Signed-off-by: Jan Stancek <jstancek@redhat.com>
>> > ---
>> >  lib/tst_device.c | 17 ++++++++++++-----
>> >  1 file changed, 12 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/lib/tst_device.c b/lib/tst_device.c
>> > index c34cbe6d1f56..414bf0eea816 100644
>> > --- a/lib/tst_device.c
>> > +++ b/lib/tst_device.c
>> > @@ -506,12 +506,17 @@ unsigned long tst_dev_bytes_written(const char *dev)
>> >       return dev_bytes_written;
>> >  }
>> >
>> > -static int count_match_len(const char *first, const char *second)
>> > +static int str_starts_with(const char *str, const char *prefix)
>> >  {
>> >       int len = 0;
>> >
>> > -     while (*first && *first++ == *second++)
>> > +     while (*prefix) {
>> > +             if (!*str)
>> > +                     return 0;
>> > +             if (*str++ != *prefix++)
>> > +                     return 0;
>> >               len++;
>> > +     }
>>
>> I'm not sure this is better than the original. It's a seperate cleanup
>> in any case.
>
> The difference is that partial matches now returns 0. Previously it did not,
> it only counted number of matching characters. So for example ("/foobar" "/foo")
> appeared as better match than ("/foobar", "/")

Ah, sorry.

>
>>
>> >
>> >       return len;
>> >  }
>> > @@ -524,7 +529,7 @@ void tst_find_backing_dev(const char *path, char *dev)
>> >       char *pre = NULL;
>> >       char *next = NULL;
>> >       unsigned int dev_major, dev_minor, line_mjr, line_mnr;
>> > -     unsigned int len, best_match_len = 1;
>> > +     unsigned int len, best_match_len = 0;
>> >       char mnt_point[PATH_MAX];
>> >
>> >       if (stat(path, &buf) < 0)
>> > @@ -550,7 +555,7 @@ void tst_find_backing_dev(const char *path, char *dev)
>> >                       break;
>> >               }
>> >
>> > -             len = count_match_len(path, mnt_point);
>> > +             len = str_starts_with(path, mnt_point);
>> >               if (len > best_match_len) {
>> >                       strcpy(dev, pre);
>> >                       best_match_len = len;
>> > @@ -559,8 +564,10 @@ void tst_find_backing_dev(const char *path, char *dev)
>> >
>> >       SAFE_FCLOSE(NULL, file);
>> >
>> > -     if (!*dev)
>> > +     if (!*dev) {
>> > +             tst_system("cat /proc/self/mountinfo");
>> >               tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
>> > +     }
>> >
>> >       if (stat(dev, &buf) < 0)
>> >               tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
>> > --
>> > 2.27.0
>>
>> Makes sense. However I suspect this function can be replaced with the
>> standard library method used in tst_stat_mount_dev. I didn't try this
>> before because I'm not sure why it scans mountinfo instead of mounts.
>
> /proc/self/mounts doesn't contain major/minor numbers, which is primarily what
> tst_find_backing_dev is using.

Does anyone know a situation where checking the mount path doesn't work?
It seems like we are just checking the device numbers first for
historical reasons and not because it is necessary.

I haven't seen any failure reports for io_control01 which only checks
the path with tst_stat_mount_dev. However this test only runs if you
have CG v2 enabled by default.

>
>>
>>
>> --
>> Thank you,
>> Richard.
>>
Jan Stancek July 19, 2022, 9:07 a.m. UTC | #5
On Mon, Jul 11, 2022 at 3:21 PM Richard Palethorpe <rpalethorpe@suse.de> wrote:
>
> Hello,
>
> Jan Stancek <jstancek@redhat.com> writes:
>
> > On Mon, Jul 11, 2022 at 2:13 PM Richard Palethorpe <rpalethorpe@suse.de> wrote:
> >>
> >> Hello,
> >>
> >> Jan Stancek <jstancek@redhat.com> writes:
> >>
> >> > If backing dev is btrfs root device, then starting best_match_len
> >> > from 1 creates an issue, because root (/) is never matched.
> >> > Also we should check that entire mount point string is present in
> >> > path we are matching against.
> >> >
> >> > In case there's error also dump /proc/self/mountinfo before tst_brk.
> >> >
> >> > This fixes test with following partition layout (TMPDIR is on /):
> >> >   # cat /proc/self/mountinfo  | grep btrfs
> >> >   59 1 0:29 /root / rw,relatime shared:1 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=257,subvol=/root
> >> >   93 59 0:29 /home /home rw,relatime shared:47 - btrfs /dev/dasda2 rw,seclabel,compress=zstd:1,ssd,space_cache=v2,subvolid=256,subvol=/home
> >> >
> >> > Signed-off-by: Jan Stancek <jstancek@redhat.com>
> >> > ---
> >> >  lib/tst_device.c | 17 ++++++++++++-----
> >> >  1 file changed, 12 insertions(+), 5 deletions(-)
> >> >
> >> > diff --git a/lib/tst_device.c b/lib/tst_device.c
> >> > index c34cbe6d1f56..414bf0eea816 100644
> >> > --- a/lib/tst_device.c
> >> > +++ b/lib/tst_device.c
> >> > @@ -506,12 +506,17 @@ unsigned long tst_dev_bytes_written(const char *dev)
> >> >       return dev_bytes_written;
> >> >  }
> >> >
> >> > -static int count_match_len(const char *first, const char *second)
> >> > +static int str_starts_with(const char *str, const char *prefix)
> >> >  {
> >> >       int len = 0;
> >> >
> >> > -     while (*first && *first++ == *second++)
> >> > +     while (*prefix) {
> >> > +             if (!*str)
> >> > +                     return 0;
> >> > +             if (*str++ != *prefix++)
> >> > +                     return 0;
> >> >               len++;
> >> > +     }
> >>
> >> I'm not sure this is better than the original. It's a seperate cleanup
> >> in any case.
> >
> > The difference is that partial matches now returns 0. Previously it did not,
> > it only counted number of matching characters. So for example ("/foobar" "/foo")
> > appeared as better match than ("/foobar", "/")
>
> Ah, sorry.
>
> >
> >>
> >> >
> >> >       return len;
> >> >  }
> >> > @@ -524,7 +529,7 @@ void tst_find_backing_dev(const char *path, char *dev)
> >> >       char *pre = NULL;
> >> >       char *next = NULL;
> >> >       unsigned int dev_major, dev_minor, line_mjr, line_mnr;
> >> > -     unsigned int len, best_match_len = 1;
> >> > +     unsigned int len, best_match_len = 0;
> >> >       char mnt_point[PATH_MAX];
> >> >
> >> >       if (stat(path, &buf) < 0)
> >> > @@ -550,7 +555,7 @@ void tst_find_backing_dev(const char *path, char *dev)
> >> >                       break;
> >> >               }
> >> >
> >> > -             len = count_match_len(path, mnt_point);
> >> > +             len = str_starts_with(path, mnt_point);
> >> >               if (len > best_match_len) {
> >> >                       strcpy(dev, pre);
> >> >                       best_match_len = len;
> >> > @@ -559,8 +564,10 @@ void tst_find_backing_dev(const char *path, char *dev)
> >> >
> >> >       SAFE_FCLOSE(NULL, file);
> >> >
> >> > -     if (!*dev)
> >> > +     if (!*dev) {
> >> > +             tst_system("cat /proc/self/mountinfo");
> >> >               tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
> >> > +     }
> >> >
> >> >       if (stat(dev, &buf) < 0)
> >> >               tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
> >> > --
> >> > 2.27.0
> >>
> >> Makes sense. However I suspect this function can be replaced with the
> >> standard library method used in tst_stat_mount_dev. I didn't try this
> >> before because I'm not sure why it scans mountinfo instead of mounts.
> >
> > /proc/self/mounts doesn't contain major/minor numbers, which is primarily what
> > tst_find_backing_dev is using.
>
> Does anyone know a situation where checking the mount path doesn't work?

You could mount multiple times to same mount path, which would make it harder
to find the right one.

> It seems like we are just checking the device numbers first for
> historical reasons and not because it is necessary.

Device numbers seem slightly less ambiguous.

>
> I haven't seen any failure reports for io_control01 which only checks
> the path with tst_stat_mount_dev. However this test only runs if you
> have CG v2 enabled by default.
>
> >
> >>
> >>
> >> --
> >> Thank you,
> >> Richard.
> >>
>
>
> --
> Thank you,
> Richard.
>
diff mbox series

Patch

diff --git a/lib/tst_device.c b/lib/tst_device.c
index c34cbe6d1f56..414bf0eea816 100644
--- a/lib/tst_device.c
+++ b/lib/tst_device.c
@@ -506,12 +506,17 @@  unsigned long tst_dev_bytes_written(const char *dev)
 	return dev_bytes_written;
 }
 
-static int count_match_len(const char *first, const char *second)
+static int str_starts_with(const char *str, const char *prefix)
 {
 	int len = 0;
 
-	while (*first && *first++ == *second++)
+	while (*prefix) {
+		if (!*str)
+			return 0;
+		if (*str++ != *prefix++)
+			return 0;
 		len++;
+	}
 
 	return len;
 }
@@ -524,7 +529,7 @@  void tst_find_backing_dev(const char *path, char *dev)
 	char *pre = NULL;
 	char *next = NULL;
 	unsigned int dev_major, dev_minor, line_mjr, line_mnr;
-	unsigned int len, best_match_len = 1;
+	unsigned int len, best_match_len = 0;
 	char mnt_point[PATH_MAX];
 
 	if (stat(path, &buf) < 0)
@@ -550,7 +555,7 @@  void tst_find_backing_dev(const char *path, char *dev)
 			break;
 		}
 
-		len = count_match_len(path, mnt_point);
+		len = str_starts_with(path, mnt_point);
 		if (len > best_match_len) {
 			strcpy(dev, pre);
 			best_match_len = len;
@@ -559,8 +564,10 @@  void tst_find_backing_dev(const char *path, char *dev)
 
 	SAFE_FCLOSE(NULL, file);
 
-	if (!*dev)
+	if (!*dev) {
+		tst_system("cat /proc/self/mountinfo");
 		tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
+	}
 
 	if (stat(dev, &buf) < 0)
 		tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);