Re: About VFS locking strategy...

2006-01-18 Thread Kris Kennaway
On Thu, Jan 19, 2006 at 08:43:55AM +0900, Shin,Hee-Sub wrote:
> Hi all. 
> 
>  
> 
> I'm speluking with source code of FreeBSD now, comparing VFS of FBSD and
> the linux's. 
> 
>  
> 
> I have a question related with concurrent accesses to the file system. It
> is seemed that VFS locks and unlocks each VNODEs before calling VNODE OPS
> provided by underlying FS. For example, it calls vn_lock(vp, ...) before
> jumps to VOP_READ() in vn_read(). 
> 
>  
> 
> WindowsCE kernel also has a component that is responsible for switching FS
> requests to appropriate file-system underlying and similar with VFS of many
> UNIX variants, but it's not perfectly same. In WindowsCE world, file system
> driver code can be called on re-entry and file system programmer should
> keep this in mind. The manager does not manage any synchronization problems
> that can be occurred when multiple threads access to the file system. It
> has only a few locks for protecting its own data structures. 
> 
>  
> 
> How does it manage synchronization problems in the VFS of FreeBSD? 
> 
>  
> 
> Please give me a detailed description about lock strategy the FreeBSD uses. 

This question might be too general to get any replies, but it would
still be better asked on fs@ or [EMAIL PROTECTED]

Kris

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About VFS locking strategy...

2006-01-18 Thread Shin,Hee-Sub
Hi all. 

 

I'm speluking with source code of FreeBSD now, comparing VFS of FBSD and
the linux's. 

 

I have a question related with concurrent accesses to the file system. It
is seemed that VFS locks and unlocks each VNODEs before calling VNODE OPS
provided by underlying FS. For example, it calls vn_lock(vp, ...) before
jumps to VOP_READ() in vn_read(). 

 

WindowsCE kernel also has a component that is responsible for switching FS
requests to appropriate file-system underlying and similar with VFS of many
UNIX variants, but it's not perfectly same. In WindowsCE world, file system
driver code can be called on re-entry and file system programmer should
keep this in mind. The manager does not manage any synchronization problems
that can be occurred when multiple threads access to the file system. It
has only a few locks for protecting its own data structures. 

 

How does it manage synchronization problems in the VFS of FreeBSD? 

 

Please give me a detailed description about lock strategy the FreeBSD uses. 

 

 

Thanks in advance. 

Charlie

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