[PATCH 5.15 002/106] nfsd: Replace use of rwsem with errseq_t

Greg Kroah-Hartman
2022-06-20T13:21:49Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb upstream.

The nfsd_file nf_rwsem is currently being used to separate file write
and commit instances to ensure that we catch errors and apply them to
the correct write/commit.
We can improve scalability at the expense of a little accuracy (some
extra false positives) by replacing the nf_rwsem with more careful
use of the errseq_t mechanism to track errors across the different
operations.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[ cel: rebased on zero-verifier fix ]
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/nfsd/filecache.c | 1 -
fs/nfsd/filecache.h | 1 -
fs/nfsd/nfs4proc.c | 16 +++++++++-------
fs/nfsd/vfs.c | 40 +++++++++++++++-------------------------
4 files changed, 24 insertions(+), 34 deletions(-)

--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -194,7 +194,6 @@ nfsd_file_alloc(struct inode *inode, uns
__set_bit(NFSD_FILE_BREAK_READ, &nf->nf_flags);
}
nf->nf_mark = NULL;
- init_rwsem(&nf->nf_rwsem);
trace_nfsd_file_alloc(nf);
}
return nf;
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -46,7 +46,6 @@ struct nfsd_file {
refcount_t nf_ref;
unsigned char nf_may;
struct nfsd_file_mark *nf_mark;
- struct rw_semaphore nf_rwsem;
};

int nfsd_file_cache_init(void);
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1515,6 +1515,9 @@ static void nfsd4_init_copy_res(struct n

static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
{
+ struct file *dst = copy->nf_dst->nf_file;
+ struct file *src = copy->nf_src->nf_file;
+ errseq_t since;
ssize_t bytes_copied = 0;
u64 bytes_total = copy->cp_count;
u64 src_pos = copy->cp_src_pos;
@@ -1527,9 +1530,8 @@ static ssize_t _nfsd_copy_file_range(str
do {
if (kthread_should_stop())
break;
- bytes_copied = nfsd_copy_file_range(copy->nf_src->nf_file,
- src_pos, copy->nf_dst->nf_file, dst_pos,
- bytes_total);
+ bytes_copied = nfsd_copy_file_range(src, src_pos, dst, dst_pos,
+ bytes_total);
if (bytes_copied <= 0)
break;
bytes_total -= bytes_copied;
@@ -1539,11 +1541,11 @@ static ssize_t _nfsd_copy_file_range(str
} while (bytes_total > 0 && !copy->cp_synchronous);
/* for a non-zero asynchronous copy do a commit of data */
if (!copy->cp_synchronous && copy->cp_res.wr_bytes_written > 0) {
- down_write(&copy->nf_dst->nf_rwsem);
- status = vfs_fsync_range(copy->nf_dst->nf_file,
- copy->cp_dst_pos,
+ since = READ_ONCE(dst->f_wb_err);
+ status = vfs_fsync_range(dst, copy->cp_dst_pos,
copy->cp_res.wr_bytes_written, 0);
- up_write(&copy->nf_dst->nf_rwsem);
+ if (!status)
+ status = filemap_check_wb_err(dst->f_mapping, since);
if (!status)
copy->committed = true;
}
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -525,10 +525,11 @@ __be32 nfsd4_clone_file_range(struct nfs
{
struct file *src = nf_src->nf_file;
struct file *dst = nf_dst->nf_file;
+ errseq_t since;
loff_t cloned;
__be32 ret = 0;

- down_write(&nf_dst->nf_rwsem);
+ since = READ_ONCE(dst->f_wb_err);
cloned = vfs_clone_file_range(src, src_pos, dst, dst_pos, count, 0);
if (cloned < 0) {
ret = nfserrno(cloned);
@@ -543,6 +544,8 @@ __be32 nfsd4_clone_file_range(struct nfs
int status = vfs_fsync_range(dst, dst_pos, dst_end, 0);

if (!status)
+ status = filemap_check_wb_err(dst->f_mapping, since);
+ if (!status)
status = commit_inode_metadata(file_inode(src));
if (status < 0) {
nfsd_reset_boot_verifier(net_generic(nf_dst->nf_net,
@@ -551,7 +554,6 @@ __be32 nfsd4_clone_file_range(struct nfs
}
}
out_err:
- up_write(&nf_dst->nf_rwsem);
return ret;
}

@@ -954,6 +956,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
struct super_block *sb = file_inode(file)->i_sb;
struct svc_export *exp;
struct iov_iter iter;
+ errseq_t since;
__be32 nfserr;
int host_err;
int use_wgather;
@@ -991,8 +994,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
flags |= RWF_SYNC;

iov_iter_kvec(&iter, WRITE, vec, vlen, *cnt);
+ since = READ_ONCE(file->f_wb_err);
if (flags & RWF_SYNC) {
- down_write(&nf->nf_rwsem);
if (verf)
nfsd_copy_boot_verifier(verf,
net_generic(SVC_NET(rqstp),
@@ -1001,15 +1004,12 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
if (host_err < 0)
nfsd_reset_boot_verifier(net_generic(SVC_NET(rqstp),
nfsd_net_id));
- up_write(&nf->nf_rwsem);
} else {
- down_read(&nf->nf_rwsem);
if (verf)
nfsd_copy_boot_verifier(verf,
net_generic(SVC_NET(rqstp),
nfsd_net_id));
host_err = vfs_iter_write(file, &iter, &pos, flags);
- up_read(&nf->nf_rwsem);
}
if (host_err < 0) {
nfsd_reset_boot_verifier(net_generic(SVC_NET(rqstp),
@@ -1019,6 +1019,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
*cnt = host_err;
nfsd_stats_io_write_add(exp, *cnt);
fsnotify_modify(file);
+ host_err = filemap_check_wb_err(file->f_mapping, since);
+ if (host_err < 0)
+ goto out_nfserr;

if (stable && use_wgather) {
host_err = wait_for_concurrent_writes(file);
@@ -1099,19 +1102,6 @@ out:
}

#ifdef CONFIG_NFSD_V3
-static int
-nfsd_filemap_write_and_wait_range(struct nfsd_file *nf, loff_t offset,
- loff_t end)
-{
- struct address_space *mapping = nf->nf_file->f_mapping;
- int ret = filemap_fdatawrite_range(mapping, offset, end);
-
- if (ret)
- return ret;
- filemap_fdatawait_range_keep_errors(mapping, offset, end);
- return 0;
-}
-
/*
* Commit all pending writes to stable storage.
*
@@ -1142,25 +1132,25 @@ nfsd_commit(struct svc_rqst *rqstp, stru
if (err)
goto out;
if (EX_ISSYNC(fhp->fh_export)) {
- int err2 = nfsd_filemap_write_and_wait_range(nf, offset, end);
+ errseq_t since = READ_ONCE(nf->nf_file->f_wb_err);
+ int err2;

- down_write(&nf->nf_rwsem);
- if (!err2)
- err2 = vfs_fsync_range(nf->nf_file, offset, end, 0);
+ err2 = vfs_fsync_range(nf->nf_file, offset, end, 0);
switch (err2) {
case 0:
nfsd_copy_boot_verifier(verf, net_generic(nf->nf_net,
nfsd_net_id));
+ err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
+ since);
break;
case -EINVAL:
err = nfserr_notsupp;
break;
default:
- err = nfserrno(err2);
nfsd_reset_boot_verifier(net_generic(nf->nf_net,
nfsd_net_id));
}
- up_write(&nf->nf_rwsem);
+ err = nfserrno(err2);
} else
nfsd_copy_boot_verifier(verf, net_generic(nf->nf_net,
nfsd_net_id));