How to get the inode - no path_lookup
Hi All, I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel. I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed. I tried the following code then which did not work . . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1); if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; } its not returning dentry I again tried after seeing the implementation of vfs_stat function user_path_at(AT_FDCWD, filename, lookup_flags, &path); but this also fails. I am using a proc interface to pass the filename, and copying the filename into a kernel buffer. How can I get a copy of vfs inode for a file name. -- Regards, Rishi Agrawal
On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
Hi All,
I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel.
I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed.
I tried the following code then which did not work
. . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; }
its not returning dentry
I again tried after seeing the implementation of vfs_stat function
user_path_at(AT_FDCWD, filename, lookup_flags, &path);
but this also fails.
I am using a proc interface to pass the filename, and copying the filename into a kernel buffer.
How can I get a copy of vfs inode for a file name.
Need to use vfs_path_lookup for this, present in fs/namei.c file, which would give you filled nameidata nd that contais inodes pointer.
-- Regards, Rishi Agrawal
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- Rohan
On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15@gmail.com> wrote:
On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
Hi All,
I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel.
I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed.
I tried the following code then which did not work
. . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; }
its not returning dentry
I again tried after seeing the implementation of vfs_stat function
user_path_at(AT_FDCWD, filename, lookup_flags, &path);
but this also fails.
I am using a proc interface to pass the filename, and copying the filename into a kernel buffer.
How can I get a copy of vfs inode for a file name.
Need to use vfs_path_lookup for this, present in fs/namei.c file, which would give you filled nameidata nd that contais inodes pointer.
-- Regards, Rishi Agrawal
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
- Rohan
vfs_path_lookup needs a dentry/mountpoint for the current path. How will I get those. /** * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair * @dentry: pointer to dentry of the base directory * @mnt: pointer to vfs mount of the base directory * @name: pointer to file name * @flags: lookup flags * @path: pointer to struct path to fill */ -- Regards, Rishi Agrawal
On Thu, Aug 9, 2012 at 8:45 AM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
Hi All,
I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel.
I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed.
I tried the following code then which did not work
. . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; }
its not returning dentry
I again tried after seeing the implementation of vfs_stat function
user_path_at(AT_FDCWD, filename, lookup_flags, &path);
but this also fails.
I am using a proc interface to pass the filename, and copying the filename into a kernel buffer.
How can I get a copy of vfs inode for a file name.
Need to use vfs_path_lookup for this, present in fs/namei.c file, which would give you filled nameidata nd that contais inodes pointer.
-- Regards, Rishi Agrawal
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
- Rohan
vfs_path_lookup needs a dentry/mountpoint for the current path.
How will I get those.
/** * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair * @dentry: pointer to dentry of the base directory * @mnt: pointer to vfs mount of the base directory * @name: pointer to file name * @flags: lookup flags * @path: pointer to struct path to fill */
-- Regards, Rishi Agrawal
If you dont have vfsmount's ptr, then you can make use of kern_path api
with the LOOKUP_FOLLOW as second parameter. This will return the struct path ptr which contains vfsmount and the dentry's ptr. Now the dentry's ptr will contain the inode that you require. - Rohan
On Thu, Aug 9, 2012 at 12:39 PM, Rohan Puri <rohan.puri15@gmail.com> wrote:
On Thu, Aug 9, 2012 at 8:45 AM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com
wrote:
Hi All,
I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel.
I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed.
I tried the following code then which did not work
. . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; }
its not returning dentry
I again tried after seeing the implementation of vfs_stat function
user_path_at(AT_FDCWD, filename, lookup_flags, &path);
but this also fails.
I am using a proc interface to pass the filename, and copying the filename into a kernel buffer.
How can I get a copy of vfs inode for a file name.
Need to use vfs_path_lookup for this, present in fs/namei.c file, which would give you filled nameidata nd that contais inodes pointer.
-- Regards, Rishi Agrawal
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
- Rohan
vfs_path_lookup needs a dentry/mountpoint for the current path.
How will I get those.
/** * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair * @dentry: pointer to dentry of the base directory * @mnt: pointer to vfs mount of the base directory * @name: pointer to file name * @flags: lookup flags * @path: pointer to struct path to fill */
-- Regards, Rishi Agrawal
If you dont have vfsmount's ptr, then you can make use of kern_path api
with the LOOKUP_FOLLOW as second parameter. This will return the struct path ptr which contains vfsmount and the dentry's ptr. Now the dentry's ptr will contain the inode that you require.
- Rohan
Thanks, used that and its working now -- Regards, Rishi Agrawal
On Mon, Aug 13, 2012 at 2:17 PM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
On Thu, Aug 9, 2012 at 12:39 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
On Thu, Aug 9, 2012 at 8:45 AM, Rishi Agrawal <rishi.b.agrawal@gmail.com>wrote:
On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15@gmail.com>wrote:
On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal < rishi.b.agrawal@gmail.com> wrote:
Hi All,
I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel.
I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed.
I tried the following code then which did not work
. . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; }
its not returning dentry
I again tried after seeing the implementation of vfs_stat function
user_path_at(AT_FDCWD, filename, lookup_flags, &path);
but this also fails.
I am using a proc interface to pass the filename, and copying the filename into a kernel buffer.
How can I get a copy of vfs inode for a file name.
Need to use vfs_path_lookup for this, present in fs/namei.c file, which would give you filled nameidata nd that contais inodes pointer.
-- Regards, Rishi Agrawal
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
- Rohan
vfs_path_lookup needs a dentry/mountpoint for the current path.
How will I get those.
/** * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair * @dentry: pointer to dentry of the base directory * @mnt: pointer to vfs mount of the base directory * @name: pointer to file name * @flags: lookup flags * @path: pointer to struct path to fill */
-- Regards, Rishi Agrawal
If you dont have vfsmount's ptr, then you can make use of kern_path api
with the LOOKUP_FOLLOW as second parameter. This will return the struct path ptr which contains vfsmount and the dentry's ptr. Now the dentry's ptr will contain the inode that you require.
- Rohan
Thanks, used that and its working now
-- Regards, Rishi Agrawal
Good to know :)
- Rohan
Hi, I happened to come across this discussion. I am having a similar issue. I am using Rhel7-3.10.0-123 kernel. I tried all the options that are mentioned above and none of the api's including kern_path() return valid dentry value. My requirement is to fetch directory name from filepath. Can anybody suggest a work-around for this ?
On Fri, Sep 04, 2015 at 04:26:06PM +0000, priyamn wrote:
Hi,
I happened to come across this discussion. I am having a similar issue. I am using Rhel7-3.10.0-123 kernel. I tried all the options that are mentioned above and none of the api's including kern_path() return valid dentry value. My requirement is to fetch directory name from filepath.
Why do you need a directory name from a filepath within the kernel? What problem are you trying to solve that you feel a directory name is the correct solution? And remember, namespaces, what does a "directory name" really mean... :) thanks, greg k-h
On 17 Sep 2015 04:02, "Greg KH" <greg@kroah.com> wrote:
On Fri, Sep 04, 2015 at 04:26:06PM +0000, priyamn wrote:
Hi,
I happened to come across this discussion. I am having a similar issue. I am using Rhel7-3.10.0-123 kernel. I tried all the options that are mentioned above and none of
the api's
including kern_path() return valid dentry value. My requirement is to fetch directory name from filepath.
Why do you need a directory name from a filepath within the kernel? What problem are you trying to solve that you feel a directory name is the correct solution?
And remember, namespaces, what does a "directory name" really mean... :)
thanks,
greg k-h
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Hi Priya, Please make use of a single thread for one topic. There was another thread by you on the same topic. Anyways, I am replying to this one. Greg has asked questions that you should ask yourself before going on with choosing one approach. I had suggested you using kern_path() earlier, since it doesn't makes use of nameidata, but as you are telling its not working too. Here I would like to know the actual context of the approach so as to figure out if something I know that can work for you or maybe you shouldn't be doing it that way. Enjoy life, Rohan
participants (4)
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Greg KH -
priyamn -
Rishi Agrawal -
Rohan Puri