nfsd: use short read as well as i_size to set eof
Use the result of a local read to determine when to set the eof flag. This
allows us to return the location of the end of the file atomically at the
time of the read.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
[bfields: add some documentation]
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 7b755b7..51c3b06 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -147,6 +147,7 @@
{
__be32 nfserr;
u32 max_blocksize = svc_max_payload(rqstp);
+ unsigned long cnt = min(argp->count, max_blocksize);
dprintk("nfsd: READ(3) %s %lu bytes at %Lu\n",
SVCFH_fmt(&argp->fh),
@@ -157,7 +158,7 @@
* 1 (status) + 22 (post_op_attr) + 1 (count) + 1 (eof)
* + 1 (xdr opaque byte count) = 26
*/
- resp->count = min(argp->count, max_blocksize);
+ resp->count = cnt;
svc_reserve_auth(rqstp, ((1 + NFS3_POST_OP_ATTR_WORDS + 3)<<2) + resp->count +4);
fh_copy(&resp->fh, &argp->fh);
@@ -167,8 +168,8 @@
&resp->count);
if (nfserr == 0) {
struct inode *inode = d_inode(resp->fh.fh_dentry);
-
- resp->eof = (argp->offset + resp->count) >= inode->i_size;
+ resp->eof = nfsd_eof_on_read(cnt, resp->count, argp->offset,
+ inode->i_size);
}
RETURN_STATUS(nfserr);
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index aa87954..9df898b 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3365,6 +3365,7 @@
struct xdr_stream *xdr = &resp->xdr;
struct xdr_buf *buf = xdr->buf;
u32 eof;
+ long len;
int space_left;
__be32 nfserr;
__be32 *p = xdr->p - 2;
@@ -3373,6 +3374,7 @@
if (xdr->end - xdr->p < 1)
return nfserr_resource;
+ len = maxcount;
nfserr = nfsd_splice_read(read->rd_rqstp, file,
read->rd_offset, &maxcount);
if (nfserr) {
@@ -3385,8 +3387,8 @@
return nfserr;
}
- eof = (read->rd_offset + maxcount >=
- d_inode(read->rd_fhp->fh_dentry)->i_size);
+ eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
+ d_inode(read->rd_fhp->fh_dentry)->i_size);
*(p++) = htonl(eof);
*(p++) = htonl(maxcount);
@@ -3456,14 +3458,15 @@
}
read->rd_vlen = v;
+ len = maxcount;
nfserr = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
read->rd_vlen, &maxcount);
if (nfserr)
return nfserr;
xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
- eof = (read->rd_offset + maxcount >=
- d_inode(read->rd_fhp->fh_dentry)->i_size);
+ eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
+ d_inode(read->rd_fhp->fh_dentry)->i_size);
tmp = htonl(eof);
write_bytes_to_xdr_buf(xdr->buf, starting_len , &tmp, 4);
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index c11ba31..2d573ec 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -139,4 +139,23 @@
|| createmode == NFS4_CREATE_EXCLUSIVE4_1;
}
+static inline bool nfsd_eof_on_read(long requested, long read,
+ loff_t offset, loff_t size)
+{
+ /* We assume a short read means eof: */
+ if (requested > read)
+ return true;
+ /*
+ * A non-short read might also reach end of file. The spec
+ * still requires us to set eof in that case.
+ *
+ * Further operations may have modified the file size since
+ * the read, so the following check is not atomic with the read.
+ * We've only seen that cause a problem for a client in the case
+ * where the read returned a count of 0 without setting eof.
+ * That case was fixed by the addition of the above check.
+ */
+ return (offset + read >= size);
+}
+
#endif /* LINUX_NFSD_VFS_H */