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NFSD: Insulate nfsd4_encode_fattr4() from page boundaries in the encode buffer

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Commit ab04de60ae ("NFSD: Optimize nfsd4_encode_fattr()") replaced
the use of write_bytes_to_xdr_buf() because it's expensive and the
data items to be encoded are already properly aligned.

However, there's no guarantee that the pointer returned from
xdr_reserve_space() will still point to the correct reserved space
in the encode buffer after one or more intervening calls to
xdr_reserve_space(). It just happens to work with the current
implementation of xdr_reserve_space().

This commit effectively reverts the optimization.

Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2024-12-30 19:28:56 -05:00
parent b786caa65d
commit 4163ee711c
1 changed files with 5 additions and 5 deletions
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10
fs/nfsd/nfs4xdr.c
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@ -3507,8 +3507,8 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
struct nfsd4_fattr_args args;
struct svc_fh *tempfh = NULL;
int starting_len = xdr->buf->len;
__be32 *attrlen_p, status;
int attrlen_offset;
unsigned int attrlen_offset;
__be32 attrlen, status;
u32 attrmask[3];
int err;
struct nfsd4_compoundres *resp = rqstp->rq_resp;
@ -3629,8 +3629,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
/* attr_vals */
attrlen_offset = xdr->buf->len;
attrlen_p = xdr_reserve_space(xdr, XDR_UNIT);
if (!attrlen_p)
if (unlikely(!xdr_reserve_space(xdr, XDR_UNIT)))
goto out_resource;
bitmap_from_arr32(attr_bitmap, attrmask,
ARRAY_SIZE(nfsd4_enc_fattr4_encode_ops));
@ -3640,7 +3639,8 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
if (status != nfs_ok)
goto out;
}
*attrlen_p = cpu_to_be32(xdr->buf->len - attrlen_offset - XDR_UNIT);
attrlen = cpu_to_be32(xdr->buf->len - attrlen_offset - XDR_UNIT);
write_bytes_to_xdr_buf(xdr->buf, attrlen_offset, &attrlen, XDR_UNIT);
status = nfs_ok;
out: