NFSv4.2: Rework scratch handling for READ_PLUS

Instead of using a tiny, static scratch buffer, we should use a kmalloc()-ed
buffer that is allocated when checking for read plus usage. This lets us
use the buffer before decoding any part of the READ_PLUS operation
instead of setting it right before segment decoding, meaning it should
be a little more robust.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index d80ee88..a6df815 100644 (file)
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -1122,7 +1122,6 @@ static int decode_read_plus(struct xdr_stream *xdr, struct nfs_pgio_res *res)
        uint32_t segments;
        struct read_plus_segment *segs;
        int status, i;
-       char scratch_buf[16];
        __be32 *p;
 
        status = decode_op_hdr(xdr, OP_READ_PLUS);
@@ -1143,7 +1142,6 @@ static int decode_read_plus(struct xdr_stream *xdr, struct nfs_pgio_res *res)
        if (!segs)
                return -ENOMEM;
 
-       xdr_set_scratch_buffer(xdr, &scratch_buf, sizeof(scratch_buf));
        status = -EIO;
        for (i = 0; i < segments; i++) {
                status = decode_read_plus_segment(xdr, &segs[i]);
@@ -1348,6 +1346,8 @@ static int nfs4_xdr_dec_read_plus(struct rpc_rqst *rqstp,
        struct compound_hdr hdr;
        int status;
 
+       xdr_set_scratch_buffer(xdr, res->scratch, sizeof(res->scratch));
+
        status = decode_compound_hdr(xdr, &hdr);
        if (status)
                goto out;

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 5607b1e..18f25ff 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5439,6 +5439,8 @@ static bool nfs4_read_plus_not_supported(struct rpc_task *task,
 
 static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 {
+       if (hdr->res.scratch)
+               kfree(hdr->res.scratch);
        if (!nfs4_sequence_done(task, &hdr->res.seq_res))
                return -EAGAIN;
        if (nfs4_read_stateid_changed(task, &hdr->args))
@@ -5452,17 +5454,22 @@ static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 }
 
 #if defined CONFIG_NFS_V4_2 && defined CONFIG_NFS_V4_2_READ_PLUS
-static void nfs42_read_plus_support(struct nfs_pgio_header *hdr,
+static bool nfs42_read_plus_support(struct nfs_pgio_header *hdr,
                                    struct rpc_message *msg)
 {
        /* Note: We don't use READ_PLUS with pNFS yet */
-       if (nfs_server_capable(hdr->inode, NFS_CAP_READ_PLUS) && !hdr->ds_clp)
+       if (nfs_server_capable(hdr->inode, NFS_CAP_READ_PLUS) && !hdr->ds_clp) {
                msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ_PLUS];
+               hdr->res.scratch = kmalloc(32, GFP_KERNEL);
+               return hdr->res.scratch != NULL;
+       }
+       return false;
 }
 #else
-static void nfs42_read_plus_support(struct nfs_pgio_header *hdr,
+static bool nfs42_read_plus_support(struct nfs_pgio_header *hdr,
                                    struct rpc_message *msg)
 {
+       return false;
 }
 #endif /* CONFIG_NFS_V4_2 */
 
@@ -5472,8 +5479,8 @@ static void nfs4_proc_read_setup(struct nfs_pgio_header *hdr,
        hdr->timestamp   = jiffies;
        if (!hdr->pgio_done_cb)
                hdr->pgio_done_cb = nfs4_read_done_cb;
-       msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ];
-       nfs42_read_plus_support(hdr, msg);
+       if (!nfs42_read_plus_support(hdr, msg))
+               msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ];
        nfs4_init_sequence(&hdr->args.seq_args, &hdr->res.seq_res, 0, 0);
 }
 

diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index e196ef5..29a1b39 100644 (file)
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -670,6 +670,7 @@ struct nfs_pgio_res {
                struct {
                        unsigned int            replen;         /* used by read */
                        int                     eof;            /* used by read */
+                       void *                  scratch;        /* used by read */
                };
                struct {
                        struct nfs_writeverf *  verf;           /* used by write */