On Wed, Feb 26, 2014 at 11:16 AM, Rohan Puri <rohan.puri15@xxxxxxxxx> wrote:
> _______________________________________________On Wed, Feb 26, 2014 at 1:08 AM, Abhishek Dave <cfsxdave@xxxxxxxxx> wrote:
> Hello All,
>
> Can some one please help me to understand meaning of below code
>
> <snip>
>
> if (!list_empty(&sb->s_inodes)) {
> 406 printk("VFS: Busy inodes after unmount of %s. "
> 407 "Self-destruct in 5 seconds. Have a nice
> day...\n",
> 408 sb->s_id);
> 409 }
>
> </snip>
>
> Are we doing here?
>
> Thanks,
>
> Dave
>
>
>
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Hi Abhishek,
This code gets called during unmounting of a filesystem. During
unmounting, if there are busy inodes present in the list contained in
superblock (s_inodes field), just log the error through the printk &
go forward through the unmounting process.
- Regards,
Rohan
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Well, this code is called when unmounting the file system.
When a file system is registered it will register two important functions
1. the .mount and the
2 .kill_super function. See the struct file_system_type.
1. the .mount and the
2 .kill_super function. See the struct file_system_type.
File systems generally register the kill_block_super() function to the kill_super pointer.
When kill_block_super() is called it will call generic_shutdown_super() whose task is to
1. remove the dentries related to the file system from the hash and other lists
2. sync the file system (dirty buffers, inodes and data)
3. evict the inodes from the cache. -- see function evict_inodes()
This function goes into the super block's list of inodes and collects the inodes which need to be removed from the cache and calls the dispose_list() function
4. The dispose list is the workhorse which will iterate through each inode in the list and call the registered .evict_inode function and destroy_inode function registered in the super_block.
After all this is the sb->s_inodes list has elements/inodes then there is something wrong.
It just pukes error and completes the umount operation. Generally the code will not get into this if you have not implemented your own ".destroy_inode" or ".evict_inode" function.
HTH
--
Regards,
Rishi Agrawal
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