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NFSD: Handle full-length symlinks

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I've given up on the idea of zero-copy handling of SYMLINK on the
server side. This is because the Linux VFS symlink API requires the
symlink pathname to be in a NUL-terminated kmalloc'd buffer. The
NUL-termination is going to be problematic (watching out for
landing on a page boundary and dealing with a 4096-byte pathname).

I don't believe that SYMLINK creation is on a performance path or is
requested frequently enough that it will cause noticeable CPU cache
pollution due to data copies.

There will be two places where a transport callout will be necessary
to fill in the rqstp: one will be in the svc_fill_symlink_pathname()
helper that is used by NFSv2 and NFSv3, and the other will be in
nfsd4_decode_create().

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2018-07-27 11:19:10 -04:00 • committed by J. Bruce Fields
parent 3fd9557aec
commit 11b4d66ea3
4 changed files with 32 additions and 44 deletions
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3
include/linux/sunrpc/svc.h
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@ -499,7 +499,8 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
struct page **pages,
struct kvec *first, size_t total);
char *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
struct kvec *first, size_t total);
struct kvec *first, void *p,
size_t total);
#define RPC_MAX_ADDRBUFLEN (63U)