Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, 4 Nov 2013 21:00:23 -0600
Shirish Pargaonkar wrote:
> For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try
> unset the bit DCACHE_OP_REVALIDATE of d_flags of the
> dentry. Would something like work for the mountpoint dentry?
>
>
I don't think that's the same issue at all. The problem there is that
you need to instantiate a dentry for the root of the mount on the
client, when you don't have any information about the parents.
In this case, we have dentries that are acting as mountpoints that were
getting invalidated.
>
> On Mon, Nov 4, 2013 at 7:16 PM, Jeff Layton wrote:
> > We had a couple of reports of people that are mounting NFS filesystems,
> > and then bind mounting certain local files onto dentries in that nfs
> > mount (sort of like a poor-man's unionmount).
> >
> > This all works well until the dentry serving as the mountpoint fails
> > d_revalidate. The dentry will end up being invalidated which makes the
> > bind mount unreachable via pathwalk.
> >
> > It doesn't make much sense to me to allow dentries to serve as
> > mountpoints to end up invalidated, so there's no real point in
> > attempting to d_revalidate them at all.
> >
> > Reported-by: Patrick McLean
> > Reported-by: Guang Cheng Li
> > Signed-off-by: Jeff Layton
> > ---
> > fs/namei.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index caa2805..5b10ad0 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -585,6 +585,9 @@ drop_root_mnt:
> >
> > static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
> > {
> > + /* dentries that serve as mountpoints are always considered valid */
> > + if (d_mountpoint(dentry))
> > + return 1;
> > return dentry->d_op->d_revalidate(dentry, flags);
> > }
> >
> > --
> > 1.8.3.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> > the body of a message to majord...@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
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Jeff Layton
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Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Tue, 5 Nov 2013 13:39:59 +1100
NeilBrown wrote:
> On Mon, 4 Nov 2013 20:16:26 -0500 Jeff Layton wrote:
>
> > We had a couple of reports of people that are mounting NFS filesystems,
> > and then bind mounting certain local files onto dentries in that nfs
> > mount (sort of like a poor-man's unionmount).
> >
> > This all works well until the dentry serving as the mountpoint fails
> > d_revalidate. The dentry will end up being invalidated which makes the
> > bind mount unreachable via pathwalk.
> >
> > It doesn't make much sense to me to allow dentries to serve as
> > mountpoints to end up invalidated, so there's no real point in
> > attempting to d_revalidate them at all.
> >
> > Reported-by: Patrick McLean
> > Reported-by: Guang Cheng Li
> > Signed-off-by: Jeff Layton
> > ---
> > fs/namei.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index caa2805..5b10ad0 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -585,6 +585,9 @@ drop_root_mnt:
> >
> > static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
> > {
> > + /* dentries that serve as mountpoints are always considered valid */
> > + if (d_mountpoint(dentry))
> > + return 1;
> > return dentry->d_op->d_revalidate(dentry, flags);
> > }
> >
>
> Makes sense to me. But what about the parent or grandparent of the mountpoint?
>
> Presumably we don't want to invalidate them either, and I don't think
> d_mountpoint() returns true for those, does it?
>
> NeilBrown
Good point...
I think we're probably saved there (at least on NFS) by the
check_submounts_and_drop() call in nfs_lookup_revalidate.
Hmmm, that said...I did do most of this testing on a slightly older
kernel that doesn't have that call, and I can't reproduce this problem
on a 3.12-ish kernel. I think this is probably already fixed by Miklos'
patches that added that.
Sorry for the noise!
--
Jeff Layton
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Description: PGP signature
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, Nov 04, 2013 at 09:00:23PM -0600, Shirish Pargaonkar wrote: > For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try > unset the bit DCACHE_OP_REVALIDATE of d_flags of the > dentry. Would something like work for the mountpoint dentry? The DCACHE_OP_REVALIDATE are just caches of the available dentry operations, please don't manipulate those flags on their own. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, Nov 04, 2013 at 09:00:23PM -0600, Shirish Pargaonkar wrote: For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try unset the bit DCACHE_OP_REVALIDATE of d_flags of the dentry. Would something like work for the mountpoint dentry? The DCACHE_OP_REVALIDATE are just caches of the available dentry operations, please don't manipulate those flags on their own. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Tue, 5 Nov 2013 13:39:59 +1100
NeilBrown ne...@suse.de wrote:
On Mon, 4 Nov 2013 20:16:26 -0500 Jeff Layton jlay...@redhat.com wrote:
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean chutz...@gentoo.org
Reported-by: Guang Cheng Li ligua...@cn.ibm.com
Signed-off-by: Jeff Layton jlay...@redhat.com
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry-d_op-d_revalidate(dentry, flags);
}
Makes sense to me. But what about the parent or grandparent of the mountpoint?
Presumably we don't want to invalidate them either, and I don't think
d_mountpoint() returns true for those, does it?
NeilBrown
Good point...
I think we're probably saved there (at least on NFS) by the
check_submounts_and_drop() call in nfs_lookup_revalidate.
Hmmm, that said...I did do most of this testing on a slightly older
kernel that doesn't have that call, and I can't reproduce this problem
on a 3.12-ish kernel. I think this is probably already fixed by Miklos'
patches that added that.
Sorry for the noise!
--
Jeff Layton jlay...@redhat.com
signature.asc
Description: PGP signature
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, 4 Nov 2013 21:00:23 -0600
Shirish Pargaonkar shirishpargaon...@gmail.com wrote:
For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try
unset the bit DCACHE_OP_REVALIDATE of d_flags of the
dentry. Would something like work for the mountpoint dentry?
I don't think that's the same issue at all. The problem there is that
you need to instantiate a dentry for the root of the mount on the
client, when you don't have any information about the parents.
In this case, we have dentries that are acting as mountpoints that were
getting invalidated.
On Mon, Nov 4, 2013 at 7:16 PM, Jeff Layton jlay...@redhat.com wrote:
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean chutz...@gentoo.org
Reported-by: Guang Cheng Li ligua...@cn.ibm.com
Signed-off-by: Jeff Layton jlay...@redhat.com
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry-d_op-d_revalidate(dentry, flags);
}
--
1.8.3.1
--
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--
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Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try
unset the bit DCACHE_OP_REVALIDATE of d_flags of the
dentry. Would something like work for the mountpoint dentry?
On Mon, Nov 4, 2013 at 7:16 PM, Jeff Layton wrote:
> We had a couple of reports of people that are mounting NFS filesystems,
> and then bind mounting certain local files onto dentries in that nfs
> mount (sort of like a poor-man's unionmount).
>
> This all works well until the dentry serving as the mountpoint fails
> d_revalidate. The dentry will end up being invalidated which makes the
> bind mount unreachable via pathwalk.
>
> It doesn't make much sense to me to allow dentries to serve as
> mountpoints to end up invalidated, so there's no real point in
> attempting to d_revalidate them at all.
>
> Reported-by: Patrick McLean
> Reported-by: Guang Cheng Li
> Signed-off-by: Jeff Layton
> ---
> fs/namei.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index caa2805..5b10ad0 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -585,6 +585,9 @@ drop_root_mnt:
>
> static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
> {
> + /* dentries that serve as mountpoints are always considered valid */
> + if (d_mountpoint(dentry))
> + return 1;
> return dentry->d_op->d_revalidate(dentry, flags);
> }
>
> --
> 1.8.3.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majord...@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, 4 Nov 2013 20:16:26 -0500 Jeff Layton wrote:
> We had a couple of reports of people that are mounting NFS filesystems,
> and then bind mounting certain local files onto dentries in that nfs
> mount (sort of like a poor-man's unionmount).
>
> This all works well until the dentry serving as the mountpoint fails
> d_revalidate. The dentry will end up being invalidated which makes the
> bind mount unreachable via pathwalk.
>
> It doesn't make much sense to me to allow dentries to serve as
> mountpoints to end up invalidated, so there's no real point in
> attempting to d_revalidate them at all.
>
> Reported-by: Patrick McLean
> Reported-by: Guang Cheng Li
> Signed-off-by: Jeff Layton
> ---
> fs/namei.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index caa2805..5b10ad0 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -585,6 +585,9 @@ drop_root_mnt:
>
> static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
> {
> + /* dentries that serve as mountpoints are always considered valid */
> + if (d_mountpoint(dentry))
> + return 1;
> return dentry->d_op->d_revalidate(dentry, flags);
> }
>
Makes sense to me. But what about the parent or grandparent of the mountpoint?
Presumably we don't want to invalidate them either, and I don't think
d_mountpoint() returns true for those, does it?
NeilBrown
signature.asc
Description: PGP signature
[PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean
Reported-by: Guang Cheng Li
Signed-off-by: Jeff Layton
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry->d_op->d_revalidate(dentry, flags);
}
--
1.8.3.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean chutz...@gentoo.org
Reported-by: Guang Cheng Li ligua...@cn.ibm.com
Signed-off-by: Jeff Layton jlay...@redhat.com
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry-d_op-d_revalidate(dentry, flags);
}
--
1.8.3.1
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
On Mon, 4 Nov 2013 20:16:26 -0500 Jeff Layton jlay...@redhat.com wrote:
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean chutz...@gentoo.org
Reported-by: Guang Cheng Li ligua...@cn.ibm.com
Signed-off-by: Jeff Layton jlay...@redhat.com
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry-d_op-d_revalidate(dentry, flags);
}
Makes sense to me. But what about the parent or grandparent of the mountpoint?
Presumably we don't want to invalidate them either, and I don't think
d_mountpoint() returns true for those, does it?
NeilBrown
signature.asc
Description: PGP signature
Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints
For a similar issue in cifs vfs (samba bugzilla 8950), I was going to try
unset the bit DCACHE_OP_REVALIDATE of d_flags of the
dentry. Would something like work for the mountpoint dentry?
On Mon, Nov 4, 2013 at 7:16 PM, Jeff Layton jlay...@redhat.com wrote:
We had a couple of reports of people that are mounting NFS filesystems,
and then bind mounting certain local files onto dentries in that nfs
mount (sort of like a poor-man's unionmount).
This all works well until the dentry serving as the mountpoint fails
d_revalidate. The dentry will end up being invalidated which makes the
bind mount unreachable via pathwalk.
It doesn't make much sense to me to allow dentries to serve as
mountpoints to end up invalidated, so there's no real point in
attempting to d_revalidate them at all.
Reported-by: Patrick McLean chutz...@gentoo.org
Reported-by: Guang Cheng Li ligua...@cn.ibm.com
Signed-off-by: Jeff Layton jlay...@redhat.com
---
fs/namei.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c
index caa2805..5b10ad0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -585,6 +585,9 @@ drop_root_mnt:
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ /* dentries that serve as mountpoints are always considered valid */
+ if (d_mountpoint(dentry))
+ return 1;
return dentry-d_op-d_revalidate(dentry, flags);
}
--
1.8.3.1
--
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the body of a message to majord...@vger.kernel.org
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