Re: How to safely reduce stack usage in nfs code?

[Andreas Dilger]

On Oct 29, 2004  00:20 +0300, Denis Vlasenko wrote:
> I've got one stack overflow sometime ago.
> Partially due to NFS stack usage.
> 
> structs nfs_fh and nfs_fattr take together ~300 bytes
> and are one of the most frequently used:
> 
> # cd fs/nfs; grep 'struct nfs_fh [a-z0-9_]*;' * ; grep 'struct nfs_fattr [a-z0-9_]*;' *
> callback.h:     struct nfs_fh fh;
> callback.h:     struct nfs_fh fh;
> dir.c:  struct nfs_fh fhandle;
> dir.c:  struct nfs_fh fhandle;
> dir.c:  struct nfs_fh fhandle;
> dir.c:  struct nfs_fh fhandle;
> dir.c:  struct nfs_fh sym_fh;
> nfsroot.c:      struct nfs_fh fh;
> dir.c:  struct nfs_fattr fattr;
> dir.c:  struct nfs_fattr fattr;
> dir.c:  struct nfs_fattr fattr;
> dir.c:  struct nfs_fattr fattr;
> dir.c:  struct nfs_fattr fattr;
> dir.c:  struct nfs_fattr sym_attr;
> inode.c:        struct nfs_fattr fattr;
> inode.c:        struct nfs_fattr fattr;
> inode.c:        struct nfs_fattr fattr;
> nfs3proc.c:             struct nfs_fattr res;
> nfs4proc.c:                     struct nfs_fattr fattr;
> 
> I can convert these into kmalloc'ed variants but hesitate to do so
> because of possible 'need to kmalloc in order to free memory for kmalloc'
> deadlocks.

Make the thread kmalloc unless it has PF_MEMALLOC set, in which case it
could get the structs from a small pool of reserved ones.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://members.shaw.ca/adilger/             http://members.shaw.ca/golinux/

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