When a new file is created under msharefs, allocate a new mm_struct
that will hold the VMAs for mshare region. Also allocate structure
to defines the mshare region and add a read operation to the file
that returns this information about the mshare region. Currently
this information is returned as a struct:
struct mshare_info {
unsigned long start;
unsigned long size;
};
This gives the start address for mshare region and its size.
Signed-off-by: Khalid Aziz <[email protected]>
---
include/uapi/linux/mman.h | 5 +++
mm/mshare.c | 64 ++++++++++++++++++++++++++++++++++++++-
2 files changed, 68 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
index f55bc680b5b0..56fe446e24b1 100644
--- a/include/uapi/linux/mman.h
+++ b/include/uapi/linux/mman.h
@@ -41,4 +41,9 @@
#define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB
#define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB
+struct mshare_info {
+ unsigned long start;
+ unsigned long size;
+};
+
#endif /* _UAPI_LINUX_MMAN_H */
diff --git a/mm/mshare.c b/mm/mshare.c
index 2d5924d39221..d238b68b0576 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -22,8 +22,14 @@
#include <uapi/linux/magic.h>
#include <uapi/linux/limits.h>
#include <uapi/linux/mman.h>
+#include <linux/sched/mm.h>
static struct super_block *msharefs_sb;
+struct mshare_data {
+ struct mm_struct *mm;
+ refcount_t refcnt;
+ struct mshare_info *minfo;
+};
static const struct inode_operations msharefs_dir_inode_ops;
static const struct inode_operations msharefs_file_inode_ops;
@@ -34,8 +40,29 @@ msharefs_open(struct inode *inode, struct file *file)
return simple_open(inode, file);
}
+static ssize_t
+msharefs_read(struct kiocb *iocb, struct iov_iter *iov)
+{
+ struct mshare_data *info = iocb->ki_filp->private_data;
+ size_t ret;
+ struct mshare_info m_info;
+
+ if (info->minfo != NULL) {
+ m_info.start = info->minfo->start;
+ m_info.size = info->minfo->size;
+ } else {
+ m_info.start = 0;
+ m_info.size = 0;
+ }
+ ret = copy_to_iter(&m_info, sizeof(m_info), iov);
+ if (!ret)
+ return -EFAULT;
+ return ret;
+}
+
static const struct file_operations msharefs_file_operations = {
.open = msharefs_open,
+ .read_iter = msharefs_read,
.llseek = no_llseek,
};
@@ -73,12 +100,43 @@ static struct dentry
return ERR_PTR(-ENOMEM);
}
+static int
+msharefs_fill_mm(struct inode *inode)
+{
+ struct mm_struct *mm;
+ struct mshare_data *info = NULL;
+ int retval = 0;
+
+ mm = mm_alloc();
+ if (!mm) {
+ retval = -ENOMEM;
+ goto err_free;
+ }
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info) {
+ retval = -ENOMEM;
+ goto err_free;
+ }
+ info->mm = mm;
+ info->minfo = NULL;
+ refcount_set(&info->refcnt, 1);
+ inode->i_private = info;
+
+ return 0;
+
+err_free:
+ if (mm)
+ mmput(mm);
+ kfree(info);
+ return retval;
+}
+
static struct inode
*msharefs_get_inode(struct super_block *sb, const struct inode *dir,
umode_t mode)
{
struct inode *inode = new_inode(sb);
-
if (inode) {
inode->i_ino = get_next_ino();
inode_init_owner(&init_user_ns, inode, dir, mode);
@@ -89,6 +147,10 @@ static struct inode
case S_IFREG:
inode->i_op = &msharefs_file_inode_ops;
inode->i_fop = &msharefs_file_operations;
+ if (msharefs_fill_mm(inode) != 0) {
+ discard_new_inode(inode);
+ inode = ERR_PTR(-ENOMEM);
+ }
break;
case S_IFDIR:
inode->i_op = &msharefs_dir_inode_ops;
--
2.32.0
On Wed, Jun 29, 2022 at 04:53:55PM -0600, Khalid Aziz wrote:
> When a new file is created under msharefs, allocate a new mm_struct
> that will hold the VMAs for mshare region. Also allocate structure
> to defines the mshare region and add a read operation to the file
> that returns this information about the mshare region. Currently
> this information is returned as a struct:
>
> struct mshare_info {
> unsigned long start;
> unsigned long size;
> };
>
> This gives the start address for mshare region and its size.
>
> Signed-off-by: Khalid Aziz <[email protected]>
> ---
> include/uapi/linux/mman.h | 5 +++
> mm/mshare.c | 64 ++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 68 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
> index f55bc680b5b0..56fe446e24b1 100644
> --- a/include/uapi/linux/mman.h
> +++ b/include/uapi/linux/mman.h
> @@ -41,4 +41,9 @@
> #define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB
> #define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB
>
> +struct mshare_info {
> + unsigned long start;
> + unsigned long size;
You might want to make these explicitly u64, since this is userspace
ABI and you never know when someone will want to do something crazy like
run 32-bit programs with mshare files.
Also you might want to add some padding fields for flags, future
expansion, etc.
> +};
> +
> #endif /* _UAPI_LINUX_MMAN_H */
> diff --git a/mm/mshare.c b/mm/mshare.c
> index 2d5924d39221..d238b68b0576 100644
> --- a/mm/mshare.c
> +++ b/mm/mshare.c
> @@ -22,8 +22,14 @@
> #include <uapi/linux/magic.h>
> #include <uapi/linux/limits.h>
> #include <uapi/linux/mman.h>
> +#include <linux/sched/mm.h>
>
> static struct super_block *msharefs_sb;
> +struct mshare_data {
> + struct mm_struct *mm;
> + refcount_t refcnt;
> + struct mshare_info *minfo;
> +};
>
> static const struct inode_operations msharefs_dir_inode_ops;
> static const struct inode_operations msharefs_file_inode_ops;
> @@ -34,8 +40,29 @@ msharefs_open(struct inode *inode, struct file *file)
> return simple_open(inode, file);
> }
>
> +static ssize_t
> +msharefs_read(struct kiocb *iocb, struct iov_iter *iov)
> +{
> + struct mshare_data *info = iocb->ki_filp->private_data;
> + size_t ret;
> + struct mshare_info m_info;
> +
> + if (info->minfo != NULL) {
> + m_info.start = info->minfo->start;
> + m_info.size = info->minfo->size;
> + } else {
> + m_info.start = 0;
> + m_info.size = 0;
Hmmm, read()ing out the shared mapping information. Heh.
When does this case happen? Is it before anybody mmaps this file into
an address space?
> + }
> + ret = copy_to_iter(&m_info, sizeof(m_info), iov);
> + if (!ret)
> + return -EFAULT;
> + return ret;
> +}
> +
> static const struct file_operations msharefs_file_operations = {
> .open = msharefs_open,
> + .read_iter = msharefs_read,
> .llseek = no_llseek,
> };
>
> @@ -73,12 +100,43 @@ static struct dentry
> return ERR_PTR(-ENOMEM);
> }
>
> +static int
> +msharefs_fill_mm(struct inode *inode)
> +{
> + struct mm_struct *mm;
> + struct mshare_data *info = NULL;
> + int retval = 0;
> +
> + mm = mm_alloc();
> + if (!mm) {
> + retval = -ENOMEM;
> + goto err_free;
> + }
> +
> + info = kzalloc(sizeof(*info), GFP_KERNEL);
> + if (!info) {
> + retval = -ENOMEM;
> + goto err_free;
> + }
> + info->mm = mm;
> + info->minfo = NULL;
> + refcount_set(&info->refcnt, 1);
> + inode->i_private = info;
> +
> + return 0;
> +
> +err_free:
> + if (mm)
> + mmput(mm);
> + kfree(info);
> + return retval;
> +}
> +
> static struct inode
> *msharefs_get_inode(struct super_block *sb, const struct inode *dir,
> umode_t mode)
> {
> struct inode *inode = new_inode(sb);
> -
> if (inode) {
> inode->i_ino = get_next_ino();
> inode_init_owner(&init_user_ns, inode, dir, mode);
> @@ -89,6 +147,10 @@ static struct inode
> case S_IFREG:
> inode->i_op = &msharefs_file_inode_ops;
> inode->i_fop = &msharefs_file_operations;
> + if (msharefs_fill_mm(inode) != 0) {
> + discard_new_inode(inode);
> + inode = ERR_PTR(-ENOMEM);
Is it intentional to clobber the msharefs_fill_mm return value and
replace it with ENOMEM?
--D
> + }
> break;
> case S_IFDIR:
> inode->i_op = &msharefs_dir_inode_ops;
> --
> 2.32.0
>
On 6/30/22 15:27, Darrick J. Wong wrote:
> On Wed, Jun 29, 2022 at 04:53:55PM -0600, Khalid Aziz wrote:
>> When a new file is created under msharefs, allocate a new mm_struct
>> that will hold the VMAs for mshare region. Also allocate structure
>> to defines the mshare region and add a read operation to the file
>> that returns this information about the mshare region. Currently
>> this information is returned as a struct:
>>
>> struct mshare_info {
>> unsigned long start;
>> unsigned long size;
>> };
>>
>> This gives the start address for mshare region and its size.
>>
>> Signed-off-by: Khalid Aziz <[email protected]>
>> ---
>> include/uapi/linux/mman.h | 5 +++
>> mm/mshare.c | 64 ++++++++++++++++++++++++++++++++++++++-
>> 2 files changed, 68 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
>> index f55bc680b5b0..56fe446e24b1 100644
>> --- a/include/uapi/linux/mman.h
>> +++ b/include/uapi/linux/mman.h
>> @@ -41,4 +41,9 @@
>> #define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB
>> #define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB
>>
>> +struct mshare_info {
>> + unsigned long start;
>> + unsigned long size;
>
> You might want to make these explicitly u64, since this is userspace
> ABI and you never know when someone will want to do something crazy like
> run 32-bit programs with mshare files.
>
> Also you might want to add some padding fields for flags, future
> expansion, etc.
That sounds like a good idea. I will queue it up for next version of patch series.
>
>> +};
>> +
>> #endif /* _UAPI_LINUX_MMAN_H */
>> diff --git a/mm/mshare.c b/mm/mshare.c
>> index 2d5924d39221..d238b68b0576 100644
>> --- a/mm/mshare.c
>> +++ b/mm/mshare.c
>> @@ -22,8 +22,14 @@
>> #include <uapi/linux/magic.h>
>> #include <uapi/linux/limits.h>
>> #include <uapi/linux/mman.h>
>> +#include <linux/sched/mm.h>
>>
>> static struct super_block *msharefs_sb;
>> +struct mshare_data {
>> + struct mm_struct *mm;
>> + refcount_t refcnt;
>> + struct mshare_info *minfo;
>> +};
>>
>> static const struct inode_operations msharefs_dir_inode_ops;
>> static const struct inode_operations msharefs_file_inode_ops;
>> @@ -34,8 +40,29 @@ msharefs_open(struct inode *inode, struct file *file)
>> return simple_open(inode, file);
>> }
>>
>> +static ssize_t
>> +msharefs_read(struct kiocb *iocb, struct iov_iter *iov)
>> +{
>> + struct mshare_data *info = iocb->ki_filp->private_data;
>> + size_t ret;
>> + struct mshare_info m_info;
>> +
>> + if (info->minfo != NULL) {
>> + m_info.start = info->minfo->start;
>> + m_info.size = info->minfo->size;
>> + } else {
>> + m_info.start = 0;
>> + m_info.size = 0;
>
> Hmmm, read()ing out the shared mapping information. Heh.
>
> When does this case happen? Is it before anybody mmaps this file into
> an address space?
>
It can happen before or after the first mmap which will establish the start address and size. Hence I have to account
for both cases.
>> + }
>> + ret = copy_to_iter(&m_info, sizeof(m_info), iov);
>> + if (!ret)
>> + return -EFAULT;
>> + return ret;
>> +}
>> +
>> static const struct file_operations msharefs_file_operations = {
>> .open = msharefs_open,
>> + .read_iter = msharefs_read,
>> .llseek = no_llseek,
>> };
>>
>> @@ -73,12 +100,43 @@ static struct dentry
>> return ERR_PTR(-ENOMEM);
>> }
>>
>> +static int
>> +msharefs_fill_mm(struct inode *inode)
>> +{
>> + struct mm_struct *mm;
>> + struct mshare_data *info = NULL;
>> + int retval = 0;
>> +
>> + mm = mm_alloc();
>> + if (!mm) {
>> + retval = -ENOMEM;
>> + goto err_free;
>> + }
>> +
>> + info = kzalloc(sizeof(*info), GFP_KERNEL);
>> + if (!info) {
>> + retval = -ENOMEM;
>> + goto err_free;
>> + }
>> + info->mm = mm;
>> + info->minfo = NULL;
>> + refcount_set(&info->refcnt, 1);
>> + inode->i_private = info;
>> +
>> + return 0;
>> +
>> +err_free:
>> + if (mm)
>> + mmput(mm);
>> + kfree(info);
>> + return retval;
>> +}
>> +
>> static struct inode
>> *msharefs_get_inode(struct super_block *sb, const struct inode *dir,
>> umode_t mode)
>> {
>> struct inode *inode = new_inode(sb);
>> -
>> if (inode) {
>> inode->i_ino = get_next_ino();
>> inode_init_owner(&init_user_ns, inode, dir, mode);
>> @@ -89,6 +147,10 @@ static struct inode
>> case S_IFREG:
>> inode->i_op = &msharefs_file_inode_ops;
>> inode->i_fop = &msharefs_file_operations;
>> + if (msharefs_fill_mm(inode) != 0) {
>> + discard_new_inode(inode);
>> + inode = ERR_PTR(-ENOMEM);
>
> Is it intentional to clobber the msharefs_fill_mm return value and
> replace it with ENOMEM?
ENOMEM sounded like the right value to return from msharefs_get_inode() in case of failure. On the other hand, there
isn't much of a reason to not just return the return value from msharefs_fill_mm(). I can change that.
Thanks for the review.
--
Khalid