From: Mike Snitzer <snitzer@xxxxxxxxxx>
Add 'io_cache_read' to NFSD's debugfs interface so that any data
read by NFSD will either be:
- cached using page cache (NFSD_IO_BUFFERED=0)
- cached but removed from the page cache upon completion
(NFSD_IO_DONTCACHE=1).
io_cache_read may be set by writing to:
/sys/kernel/debug/nfsd/io_cache_read
Add 'io_cache_write' to NFSD's debugfs interface so that any data
written by NFSD will either be:
- cached using page cache (NFSD_IO_BUFFERED=0)
- cached but removed from the page cache upon completion
(NFSD_IO_DONTCACHE=1).
io_cache_write may be set by writing to:
/sys/kernel/debug/nfsd/io_cache_write
The default value for both settings is NFSD_IO_BUFFERED, which is
NFSD's existing behavior for both read and write. Changes to these
settings take immediate effect for all exports and NFS versions.
Currently only xfs and ext4 implement RWF_DONTCACHE. For file
systems that do not implement RWF_DONTCACHE, NFSD use only buffered
I/O when the io_cache setting is NFSD_IO_DONTCACHE.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/nfsd/debugfs.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++
fs/nfsd/nfsd.h | 9 +++++
fs/nfsd/vfs.c | 21 +++++++++++
3 files changed, 123 insertions(+)
Changes since v1:
- Corrected patch author
- Break back to NFSD_IO_BUFFERED when exported file system does not
support RWF_DONTCACHE
- Smoke tested NFSD_IO_DONTCACHE with NFSv3,v4.0,v4.1 on xfs and
tmpfs
diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c
index 84b0c8b559dc..2b1bb716b608 100644
--- a/fs/nfsd/debugfs.c
+++ b/fs/nfsd/debugfs.c
@@ -27,11 +27,98 @@ static int nfsd_dsr_get(void *data, u64 *val)
static int nfsd_dsr_set(void *data, u64 val)
{
nfsd_disable_splice_read = (val > 0) ? true : false;
+ if (!nfsd_disable_splice_read) {
+ /*
+ * Must use buffered I/O if splice_read is enabled.
+ */
+ nfsd_io_cache_read = NFSD_IO_BUFFERED;
+ }
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%llu\n");
+/*
+ * /sys/kernel/debug/nfsd/io_cache_read
+ *
+ * Contents:
+ * %0: NFS READ will use buffered IO
+ * %1: NFS READ will use dontcache (buffered IO w/ dropbehind)
+ *
+ * This setting takes immediate effect for all NFS versions,
+ * all exports, and in all NFSD net namespaces.
+ */
+
+static int nfsd_io_cache_read_get(void *data, u64 *val)
+{
+ *val = nfsd_io_cache_read;
+ return 0;
+}
+
+static int nfsd_io_cache_read_set(void *data, u64 val)
+{
+ int ret = 0;
+
+ switch (val) {
+ case NFSD_IO_BUFFERED:
+ nfsd_io_cache_read = NFSD_IO_BUFFERED;
+ break;
+ case NFSD_IO_DONTCACHE:
+ /*
+ * Must disable splice_read when enabling
+ * NFSD_IO_DONTCACHE.
+ */
+ nfsd_disable_splice_read = true;
+ nfsd_io_cache_read = val;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get,
+ nfsd_io_cache_read_set, "%llu\n");
+
+/*
+ * /sys/kernel/debug/nfsd/io_cache_write
+ *
+ * Contents:
+ * %0: NFS WRITE will use buffered IO
+ * %1: NFS WRITE will use dontcache (buffered IO w/ dropbehind)
+ *
+ * This setting takes immediate effect for all NFS versions,
+ * all exports, and in all NFSD net namespaces.
+ */
+
+static int nfsd_io_cache_write_get(void *data, u64 *val)
+{
+ *val = nfsd_io_cache_write;
+ return 0;
+}
+
+static int nfsd_io_cache_write_set(void *data, u64 val)
+{
+ int ret = 0;
+
+ switch (val) {
+ case NFSD_IO_BUFFERED:
+ case NFSD_IO_DONTCACHE:
+ nfsd_io_cache_write = val;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_write_fops, nfsd_io_cache_write_get,
+ nfsd_io_cache_write_set, "%llu\n");
+
void nfsd_debugfs_exit(void)
{
debugfs_remove_recursive(nfsd_top_dir);
@@ -44,4 +131,10 @@ void nfsd_debugfs_init(void)
debugfs_create_file("disable-splice-read", S_IWUSR | S_IRUGO,
nfsd_top_dir, NULL, &nfsd_dsr_fops);
+
+ debugfs_create_file("io_cache_read", 0644, nfsd_top_dir, NULL,
+ &nfsd_io_cache_read_fops);
+
+ debugfs_create_file("io_cache_write", 0644, nfsd_top_dir, NULL,
+ &nfsd_io_cache_write_fops);
}
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 1cd0bed57bc2..809729d41e08 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -153,6 +153,15 @@ static inline void nfsd_debugfs_exit(void) {}
extern bool nfsd_disable_splice_read __read_mostly;
+enum {
+ /* Any new NFSD_IO enum value must be added at the end */
+ NFSD_IO_BUFFERED,
+ NFSD_IO_DONTCACHE,
+};
+
+extern u64 nfsd_io_cache_read __read_mostly;
+extern u64 nfsd_io_cache_write __read_mostly;
+
extern int nfsd_max_blksize;
static inline int nfsd_v4client(struct svc_rqst *rq)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 3cd3b9e069f4..714777c221ed 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -49,6 +49,8 @@
#define NFSDDBG_FACILITY NFSDDBG_FILEOP
bool nfsd_disable_splice_read __read_mostly;
+u64 nfsd_io_cache_read __read_mostly = NFSD_IO_BUFFERED;
+u64 nfsd_io_cache_write __read_mostly = NFSD_IO_BUFFERED;
/**
* nfserrno - Map Linux errnos to NFS errnos
@@ -1099,6 +1101,16 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
size_t len;
init_sync_kiocb(&kiocb, file);
+
+ switch (nfsd_io_cache_read) {
+ case NFSD_IO_BUFFERED:
+ break;
+ case NFSD_IO_DONTCACHE:
+ if (file->f_op->fop_flags & FOP_DONTCACHE)
+ kiocb.ki_flags = IOCB_DONTCACHE;
+ break;
+ }
+
kiocb.ki_pos = offset;
v = 0;
@@ -1224,6 +1236,15 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
since = READ_ONCE(file->f_wb_err);
if (verf)
nfsd_copy_write_verifier(verf, nn);
+
+ switch (nfsd_io_cache_write) {
+ case NFSD_IO_BUFFERED:
+ break;
+ case NFSD_IO_DONTCACHE:
+ if (file->f_op->fop_flags & FOP_DONTCACHE)
+ kiocb.ki_flags |= IOCB_DONTCACHE;
+ break;
+ }
host_err = vfs_iocb_iter_write(file, &kiocb, &iter);
if (host_err < 0) {
commit_reset_write_verifier(nn, rqstp, host_err);
--
2.50.0
