From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
This patch adds support for returning NFS4_CONTENT_HOLE segments to the
client. I did notice a race condition where the same offset can be
reported as both a hole and as data, and this patch gets around this
without a lock by encoding questionable regions as data.
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
---
fs/nfsd/nfs4xdr.c | 34 +++++++++++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 6ed22ca..2ec9860 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3800,7 +3800,7 @@ nfsd4_encode_test_stateid(struct nfsd4_compoundres *resp, __be32 nfserr,
static __be32
nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp, struct nfsd4_read *read,
- struct file *file)
+ struct file *file, loff_t hole_pos)
{
__be32 *p, err;
unsigned long maxcount;
@@ -3814,6 +3814,7 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp, struct nfsd4_read *r
maxcount = svc_max_payload(resp->rqstp);
maxcount = min_t(unsigned long, maxcount, (xdr->buf->buflen - xdr->buf->len));
maxcount = min_t(unsigned long, maxcount, read->rd_length);
+ maxcount = min_t(unsigned long, maxcount, hole_pos - read->rd_offset);
err = nfsd4_encode_readv(resp, read, file, &maxcount);
@@ -3826,6 +3827,22 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp, struct nfsd4_read *r
}
static __be32
+nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp, struct nfsd4_read *read,
+ struct file *file, loff_t data_pos)
+{
+ __be32 *p;
+ unsigned long maxcount = data_pos - read->rd_offset;
+
+ p = xdr_reserve_space(&resp->xdr, 4 + 8 + 8);
+ *p++ = cpu_to_be32(NFS4_CONTENT_HOLE);
+ p = xdr_encode_hyper(p, read->rd_offset);
+ p = xdr_encode_hyper(p, maxcount);
+
+ read->rd_offset += maxcount;
+ return nfs_ok;
+}
+
+static __be32
nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
struct nfsd4_read *read)
{
@@ -3833,6 +3850,7 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
struct file *file = read->rd_filp;
int starting_len = xdr->buf->len;
struct raparms *ra;
+ loff_t hole_pos, data_pos;
__be32 *p;
__be32 err;
u32 eof, segments = 0;
@@ -3853,10 +3871,20 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
goto err_truncate;
}
- if (read->rd_offset >= i_size_read(file_inode(file)))
+ hole_pos = vfs_llseek(read->rd_filp, read->rd_offset, SEEK_HOLE);
+ if (hole_pos == -ENXIO)
goto out_encode;
- err = nfsd4_encode_read_plus_data(resp, read, file);
+ data_pos = vfs_llseek(read->rd_filp, read->rd_offset, SEEK_DATA);
+ if (data_pos == -ENXIO)
+ data_pos = i_size_read(file_inode(file));
+
+ if ((data_pos == read->rd_offset) && (hole_pos > data_pos))
+ err = nfsd4_encode_read_plus_data(resp, read, file, hole_pos);
+ else if ((hole_pos == read->rd_offset) && (data_pos > hole_pos))
+ err = nfsd4_encode_read_plus_hole(resp, read, file, data_pos);
+ else /* The file probably changed on us between seeks. */
+ err = nfsd4_encode_read_plus_data(resp, read, file, i_size_read(file_inode(file)));
segments++;
out_encode:
--
2.1.3
--
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