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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>
This commit is contained in:
Benjamin Coddington 2016-03-22 10:28:36 -04:00 committed by J. Bruce Fields
parent 4b15da44e7
commit ac503e4a30
3 changed files with 30 additions and 7 deletions
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7
fs/nfsd/nfs3proc.c
View File

@ -147,6 +147,7 @@ nfsd3_proc_read(struct svc_rqst *rqstp, struct nfsd3_readargs *argp,
{
__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 @@ nfsd3_proc_read(struct svc_rqst *rqstp, struct nfsd3_readargs *argp,
* 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 @@ nfsd3_proc_read(struct svc_rqst *rqstp, struct nfsd3_readargs *argp,
&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);

11
fs/nfsd/nfs4xdr.c
View File

@ -3365,6 +3365,7 @@ static __be32 nfsd4_encode_splice_read(
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 @@ static __be32 nfsd4_encode_splice_read(
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 @@ static __be32 nfsd4_encode_splice_read(
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 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
}
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);

19
fs/nfsd/vfs.h
View File

@ -139,4 +139,23 @@ static inline int nfsd_create_is_exclusive(int createmode)
|| 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 */