Sync syscall to an existing DAX file needs to flush processor cache,
but it does not currently. This is because 'ext4_da_aops' is set to
address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
since S_DAX flag is set after ext4_set_aops() in the open path.
New file
--------
lookup_open
ext4_create
__ext4_new_inode
ext4_set_inode_flags // Set S_DAX flag
ext4_set_aops // Set aops to ext4_dax_aops
Existing file
-------------
lookup_open
ext4_lookup
ext4_iget
ext4_set_aops // Set aops to ext4_da_aops
ext4_set_inode_flags // Set S_DAX flag
Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
Signed-off-by: Toshi Kani <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Andreas Dilger <[email protected]>
---
fs/ext4/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 775cd9b4af55..93cbbb859c40 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
if (ret)
goto bad_inode;
+ ext4_set_inode_flags(inode);
+
if (S_ISREG(inode->i_mode)) {
inode->i_op = &ext4_file_inode_operations;
inode->i_fop = &ext4_file_operations;
@@ -5043,7 +5045,6 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
goto bad_inode;
}
brelse(iloc.bh);
- ext4_set_inode_flags(inode);
unlock_new_inode(inode);
return inode;
On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <[email protected]> wrote:
> Sync syscall to an existing DAX file needs to flush processor cache,
> but it does not currently. This is because 'ext4_da_aops' is set to
> address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
> since S_DAX flag is set after ext4_set_aops() in the open path.
>
> New file
> --------
> lookup_open
> ext4_create
> __ext4_new_inode
> ext4_set_inode_flags // Set S_DAX flag
> ext4_set_aops // Set aops to ext4_dax_aops
>
> Existing file
> -------------
> lookup_open
> ext4_lookup
> ext4_iget
> ext4_set_aops // Set aops to ext4_da_aops
> ext4_set_inode_flags // Set S_DAX flag
>
> Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
>
> Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
Same format nit:
Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
Cc: <[email protected]>
> Signed-off-by: Toshi Kani <[email protected]>
> Cc: Jan Kara <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: "Theodore Ts'o" <[email protected]>
> Cc: Andreas Dilger <[email protected]>
> ---
> fs/ext4/inode.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 775cd9b4af55..93cbbb859c40 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
> if (ret)
> goto bad_inode;
>
> + ext4_set_inode_flags(inode);
> +
Hmm, does this have unintended behavior changes?
I notice that there are some checks for flags "IS_APPEND(inode) ||
IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
didn't look too much deeper at whether those checks are bogus, but it
would seem safer to do something like this for a lower risk fix.
Thoughts?
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d0dd585add6a..1e9ab445c777 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4999,7 +4999,6 @@ struct inode *ext4_iget(struct super_block *sb,
unsigned long ino)
if (S_ISREG(inode->i_mode)) {
inode->i_op = &ext4_file_inode_operations;
inode->i_fop = &ext4_file_operations;
- ext4_set_aops(inode);
} else if (S_ISDIR(inode->i_mode)) {
inode->i_op = &ext4_dir_inode_operations;
inode->i_fop = &ext4_dir_operations;
@@ -5042,6 +5041,12 @@ struct inode *ext4_iget(struct super_block *sb,
unsigned long ino)
}
brelse(iloc.bh);
ext4_set_inode_flags(inode);
+ /*
+ * Now that we have determined whether DAX is enabled, set the
+ * proper address spaces operations
+ */
+ if (S_ISREG(inode->i_mode))
+ ext4_set_aops(inode);
unlock_new_inode(inode);
return inode;
On Tue, 2018-09-11 at 11:15 -0700, Dan Williams wrote:
> On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <[email protected]> wrote:
> > Sync syscall to an existing DAX file needs to flush processor cache,
> > but it does not currently. This is because 'ext4_da_aops' is set to
> > address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
> > since S_DAX flag is set after ext4_set_aops() in the open path.
> >
> > New file
> > --------
> > lookup_open
> > ext4_create
> > __ext4_new_inode
> > ext4_set_inode_flags // Set S_DAX flag
> > ext4_set_aops // Set aops to ext4_dax_aops
> >
> > Existing file
> > -------------
> > lookup_open
> > ext4_lookup
> > ext4_iget
> > ext4_set_aops // Set aops to ext4_da_aops
> > ext4_set_inode_flags // Set S_DAX flag
> >
> > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
> >
> > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
>
> Same format nit:
>
> Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
> Cc: <[email protected]>
Will do.
> > Signed-off-by: Toshi Kani <[email protected]>
> > Cc: Jan Kara <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: "Theodore Ts'o" <[email protected]>
> > Cc: Andreas Dilger <[email protected]>
> > ---
> > fs/ext4/inode.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 775cd9b4af55..93cbbb859c40 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
> > if (ret)
> > goto bad_inode;
> >
> > + ext4_set_inode_flags(inode);
> > +
>
> Hmm, does this have unintended behavior changes?
>
> I notice that there are some checks for flags "IS_APPEND(inode) ||
> IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
> didn't look too much deeper at whether those checks are bogus, but it
> would seem safer to do something like this for a lower risk fix.
>
> Thoughts?
Good catch! Agreed.
Thanks!
-Toshi
On Tue 11-09-18 11:15:18, Dan Williams wrote:
> On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <[email protected]> wrote:
> > Sync syscall to an existing DAX file needs to flush processor cache,
> > but it does not currently. This is because 'ext4_da_aops' is set to
> > address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
> > since S_DAX flag is set after ext4_set_aops() in the open path.
> >
> > New file
> > --------
> > lookup_open
> > ext4_create
> > __ext4_new_inode
> > ext4_set_inode_flags // Set S_DAX flag
> > ext4_set_aops // Set aops to ext4_dax_aops
> >
> > Existing file
> > -------------
> > lookup_open
> > ext4_lookup
> > ext4_iget
> > ext4_set_aops // Set aops to ext4_da_aops
> > ext4_set_inode_flags // Set S_DAX flag
> >
> > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
> >
> > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
>
> Same format nit:
>
> Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
> Cc: <[email protected]>
>
>
> > Signed-off-by: Toshi Kani <[email protected]>
> > Cc: Jan Kara <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: "Theodore Ts'o" <[email protected]>
> > Cc: Andreas Dilger <[email protected]>
> > ---
> > fs/ext4/inode.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 775cd9b4af55..93cbbb859c40 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
> > if (ret)
> > goto bad_inode;
> >
> > + ext4_set_inode_flags(inode);
> > +
>
> Hmm, does this have unintended behavior changes?
>
> I notice that there are some checks for flags "IS_APPEND(inode) ||
> IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
> didn't look too much deeper at whether those checks are bogus, but it
> would seem safer to do something like this for a lower risk fix.
>
> Thoughts?
Well, safer but it would leave the landmine around for others to hit.
Toshi, please move the ext4_set_inode_flags() call to be just after the
assignment:
ei->i_flags = le32_to_cpu(raw_inode->i_flags);
in ext4_iget(). That way people won't introduce checks for i_flags that can
never hit... And yes, it fixes also other bugs (mostly in sanity checks
AFAICS) than the DAX issue.
Honza
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d0dd585add6a..1e9ab445c777 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4999,7 +4999,6 @@ struct inode *ext4_iget(struct super_block *sb,
> unsigned long ino)
> if (S_ISREG(inode->i_mode)) {
> inode->i_op = &ext4_file_inode_operations;
> inode->i_fop = &ext4_file_operations;
> - ext4_set_aops(inode);
> } else if (S_ISDIR(inode->i_mode)) {
> inode->i_op = &ext4_dir_inode_operations;
> inode->i_fop = &ext4_dir_operations;
> @@ -5042,6 +5041,12 @@ struct inode *ext4_iget(struct super_block *sb,
> unsigned long ino)
> }
> brelse(iloc.bh);
> ext4_set_inode_flags(inode);
> + /*
> + * Now that we have determined whether DAX is enabled, set the
> + * proper address spaces operations
> + */
> + if (S_ISREG(inode->i_mode))
> + ext4_set_aops(inode);
>
> unlock_new_inode(inode);
> return inode;
--
Jan Kara <jack-IBi9RG/[email protected]>
SUSE Labs, CR
On Wed, 2018-09-12 at 11:31 +0200, Jan Kara wrote:
> On Tue 11-09-18 11:15:18, Dan Williams wrote:
> > On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <[email protected]> wrote:
> > > Sync syscall to an existing DAX file needs to flush processor cache,
> > > but it does not currently. This is because 'ext4_da_aops' is set to
> > > address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
> > > since S_DAX flag is set after ext4_set_aops() in the open path.
> > >
> > > New file
> > > --------
> > > lookup_open
> > > ext4_create
> > > __ext4_new_inode
> > > ext4_set_inode_flags // Set S_DAX flag
> > > ext4_set_aops // Set aops to ext4_dax_aops
> > >
> > > Existing file
> > > -------------
> > > lookup_open
> > > ext4_lookup
> > > ext4_iget
> > > ext4_set_aops // Set aops to ext4_da_aops
> > > ext4_set_inode_flags // Set S_DAX flag
> > >
> > > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
> > >
> > > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
> >
> > Same format nit:
> >
> > Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
> > Cc: <[email protected]>
> >
> >
> > > Signed-off-by: Toshi Kani <[email protected]>
> > > Cc: Jan Kara <[email protected]>
> > > Cc: Dan Williams <[email protected]>
> > > Cc: "Theodore Ts'o" <[email protected]>
> > > Cc: Andreas Dilger <[email protected]>
> > > ---
> > > fs/ext4/inode.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > > index 775cd9b4af55..93cbbb859c40 100644
> > > --- a/fs/ext4/inode.c
> > > +++ b/fs/ext4/inode.c
> > > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
> > > if (ret)
> > > goto bad_inode;
> > >
> > > + ext4_set_inode_flags(inode);
> > > +
> >
> > Hmm, does this have unintended behavior changes?
> >
> > I notice that there are some checks for flags "IS_APPEND(inode) ||
> > IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
> > didn't look too much deeper at whether those checks are bogus, but it
> > would seem safer to do something like this for a lower risk fix.
> >
> > Thoughts?
>
> Well, safer but it would leave the landmine around for others to hit.
> Toshi, please move the ext4_set_inode_flags() call to be just after the
> assignment:
>
> ei->i_flags = le32_to_cpu(raw_inode->i_flags);
>
> in ext4_iget(). That way people won't introduce checks for i_flags that can
> never hit... And yes, it fixes also other bugs (mostly in sanity checks
> AFAICS) than the DAX issue.
Sure. Assuming you think the implicit change Dan pointed out is not a
problem, yes, I will go with this cleaner approach.
Thanks!
-Toshi
On Wed, Sep 12, 2018 at 9:08 AM, Kani, Toshi <[email protected]> wrote:
> On Wed, 2018-09-12 at 11:31 +0200, Jan Kara wrote:
>> On Tue 11-09-18 11:15:18, Dan Williams wrote:
>> > On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <[email protected]> wrote:
>> > > Sync syscall to an existing DAX file needs to flush processor cache,
>> > > but it does not currently. This is because 'ext4_da_aops' is set to
>> > > address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
>> > > since S_DAX flag is set after ext4_set_aops() in the open path.
>> > >
>> > > New file
>> > > --------
>> > > lookup_open
>> > > ext4_create
>> > > __ext4_new_inode
>> > > ext4_set_inode_flags // Set S_DAX flag
>> > > ext4_set_aops // Set aops to ext4_dax_aops
>> > >
>> > > Existing file
>> > > -------------
>> > > lookup_open
>> > > ext4_lookup
>> > > ext4_iget
>> > > ext4_set_aops // Set aops to ext4_da_aops
>> > > ext4_set_inode_flags // Set S_DAX flag
>> > >
>> > > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
>> > >
>> > > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
>> >
>> > Same format nit:
>> >
>> > Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
>> > Cc: <[email protected]>
>> >
>> >
>> > > Signed-off-by: Toshi Kani <[email protected]>
>> > > Cc: Jan Kara <[email protected]>
>> > > Cc: Dan Williams <[email protected]>
>> > > Cc: "Theodore Ts'o" <[email protected]>
>> > > Cc: Andreas Dilger <[email protected]>
>> > > ---
>> > > fs/ext4/inode.c | 3 ++-
>> > > 1 file changed, 2 insertions(+), 1 deletion(-)
>> > >
>> > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> > > index 775cd9b4af55..93cbbb859c40 100644
>> > > --- a/fs/ext4/inode.c
>> > > +++ b/fs/ext4/inode.c
>> > > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
>> > > if (ret)
>> > > goto bad_inode;
>> > >
>> > > + ext4_set_inode_flags(inode);
>> > > +
>> >
>> > Hmm, does this have unintended behavior changes?
>> >
>> > I notice that there are some checks for flags "IS_APPEND(inode) ||
>> > IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
>> > didn't look too much deeper at whether those checks are bogus, but it
>> > would seem safer to do something like this for a lower risk fix.
>> >
>> > Thoughts?
>>
>> Well, safer but it would leave the landmine around for others to hit.
>> Toshi, please move the ext4_set_inode_flags() call to be just after the
>> assignment:
>>
>> ei->i_flags = le32_to_cpu(raw_inode->i_flags);
>>
>> in ext4_iget(). That way people won't introduce checks for i_flags that can
>> never hit... And yes, it fixes also other bugs (mostly in sanity checks
>> AFAICS) than the DAX issue.
>
> Sure. Assuming you think the implicit change Dan pointed out is not a
> problem, yes, I will go with this cleaner approach.
>
Yes, Jan's proposal looks best to me.