NFSD: Add io_cache_{read,write} controls to debugfs

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@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c
index f07d790d56aa74213e1c43831cd0faa91d86444f..ed2b9e066206b757b0df9d9086a05d69d3d0eb4b 100644 (file)
--- 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);
+       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 1cd0bed57bc2f27248fd66a8efef692a5e9a390c..809729d41e08657ab7da088af33e29a5ee89f893 100644 (file)
--- 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 3cd3b9e069f4af08e777ab10a56fb75fc2648da1..714777c221ed6087d83f7ec6195d40c5064844f9 100644 (file)
--- 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);