Commit a5864c99 authored by Trond Myklebust's avatar Trond Myklebust

NFS: Do not serialise O_DIRECT reads and writes

Allow dio requests to be scheduled in parallel, but ensuring that they
do not conflict with buffered I/O.
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 18290650
......@@ -6,7 +6,7 @@ obj-$(CONFIG_NFS_FS) += nfs.o
CFLAGS_nfstrace.o += -I$(src)
nfs-y := client.o dir.o file.o getroot.o inode.o super.o \
direct.o pagelist.o read.o symlink.o unlink.o \
io.o direct.o pagelist.o read.o symlink.o unlink.o \
write.o namespace.o mount_clnt.o nfstrace.o
nfs-$(CONFIG_ROOT_NFS) += nfsroot.o
nfs-$(CONFIG_SYSCTL) += sysctl.o
......
......@@ -578,17 +578,12 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
if (!count)
goto out;
inode_lock(inode);
result = nfs_sync_mapping(mapping);
if (result)
goto out_unlock;
task_io_account_read(count);
result = -ENOMEM;
dreq = nfs_direct_req_alloc();
if (dreq == NULL)
goto out_unlock;
goto out;
dreq->inode = inode;
dreq->bytes_left = dreq->max_count = count;
......@@ -603,10 +598,12 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
nfs_start_io_direct(inode);
NFS_I(inode)->read_io += count;
result = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
inode_unlock(inode);
nfs_end_io_direct(inode);
if (!result) {
result = nfs_direct_wait(dreq);
......@@ -614,13 +611,8 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
iocb->ki_pos += result;
}
nfs_direct_req_release(dreq);
return result;
out_release:
nfs_direct_req_release(dreq);
out_unlock:
inode_unlock(inode);
out:
return result;
}
......@@ -1008,25 +1000,12 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
pos = iocb->ki_pos;
end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
inode_lock(inode);
result = nfs_sync_mapping(mapping);
if (result)
goto out_unlock;
if (mapping->nrpages) {
result = invalidate_inode_pages2_range(mapping,
pos >> PAGE_SHIFT, end);
if (result)
goto out_unlock;
}
task_io_account_write(count);
result = -ENOMEM;
dreq = nfs_direct_req_alloc();
if (!dreq)
goto out_unlock;
goto out;
dreq->inode = inode;
dreq->bytes_left = dreq->max_count = count;
......@@ -1041,6 +1020,8 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
nfs_start_io_direct(inode);
result = nfs_direct_write_schedule_iovec(dreq, iter, pos);
if (mapping->nrpages) {
......@@ -1048,7 +1029,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
pos >> PAGE_SHIFT, end);
}
inode_unlock(inode);
nfs_end_io_direct(inode);
if (!result) {
result = nfs_direct_wait(dreq);
......@@ -1058,13 +1039,9 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
generic_write_sync(iocb, result);
}
}
nfs_direct_req_release(dreq);
return result;
out_release:
nfs_direct_req_release(dreq);
out_unlock:
inode_unlock(inode);
out:
return result;
}
......
......@@ -170,12 +170,14 @@ nfs_file_read(struct kiocb *iocb, struct iov_iter *to)
iocb->ki_filp,
iov_iter_count(to), (unsigned long) iocb->ki_pos);
result = nfs_revalidate_mapping_protected(inode, iocb->ki_filp->f_mapping);
nfs_start_io_read(inode);
result = nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
if (!result) {
result = generic_file_read_iter(iocb, to);
if (result > 0)
nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
}
nfs_end_io_read(inode);
return result;
}
EXPORT_SYMBOL_GPL(nfs_file_read);
......@@ -191,12 +193,14 @@ nfs_file_splice_read(struct file *filp, loff_t *ppos,
dprintk("NFS: splice_read(%pD2, %lu@%Lu)\n",
filp, (unsigned long) count, (unsigned long long) *ppos);
res = nfs_revalidate_mapping_protected(inode, filp->f_mapping);
nfs_start_io_read(inode);
res = nfs_revalidate_mapping(inode, filp->f_mapping);
if (!res) {
res = generic_file_splice_read(filp, ppos, pipe, count, flags);
if (res > 0)
nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, res);
}
nfs_end_io_read(inode);
return res;
}
EXPORT_SYMBOL_GPL(nfs_file_splice_read);
......@@ -645,14 +649,14 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
goto out;
}
inode_lock(inode);
nfs_start_io_write(inode);
result = generic_write_checks(iocb, from);
if (result > 0) {
current->backing_dev_info = inode_to_bdi(inode);
result = generic_perform_write(file, from, iocb->ki_pos);
current->backing_dev_info = NULL;
}
inode_unlock(inode);
nfs_end_io_write(inode);
if (result <= 0)
goto out;
......
......@@ -411,6 +411,14 @@ extern void __exit unregister_nfs_fs(void);
extern bool nfs_sb_active(struct super_block *sb);
extern void nfs_sb_deactive(struct super_block *sb);
/* io.c */
extern void nfs_start_io_read(struct inode *inode);
extern void nfs_end_io_read(struct inode *inode);
extern void nfs_start_io_write(struct inode *inode);
extern void nfs_end_io_write(struct inode *inode);
extern void nfs_start_io_direct(struct inode *inode);
extern void nfs_end_io_direct(struct inode *inode);
/* namespace.c */
#define NFS_PATH_CANONICAL 1
extern char *nfs_path(char **p, struct dentry *dentry,
......
/*
* Copyright (c) 2016 Trond Myklebust
*
* I/O and data path helper functionality.
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/rwsem.h>
#include <linux/fs.h>
#include <linux/nfs_fs.h>
#include "internal.h"
/* Call with exclusively locked inode->i_rwsem */
static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode)
{
if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
clear_bit(NFS_INO_ODIRECT, &nfsi->flags);
inode_dio_wait(inode);
}
}
/**
* nfs_start_io_read - declare the file is being used for buffered reads
* @inode - file inode
*
* Declare that a buffered read operation is about to start, and ensure
* that we block all direct I/O.
* On exit, the function ensures that the NFS_INO_ODIRECT flag is unset,
* and holds a shared lock on inode->i_rwsem to ensure that the flag
* cannot be changed.
* In practice, this means that buffered read operations are allowed to
* execute in parallel, thanks to the shared lock, whereas direct I/O
* operations need to wait to grab an exclusive lock in order to set
* NFS_INO_ODIRECT.
* Note that buffered writes and truncates both take a write lock on
* inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
*/
void
nfs_start_io_read(struct inode *inode)
{
struct nfs_inode *nfsi = NFS_I(inode);
/* Be an optimist! */
down_read(&inode->i_rwsem);
if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0)
return;
up_read(&inode->i_rwsem);
/* Slow path.... */
down_write(&inode->i_rwsem);
nfs_block_o_direct(nfsi, inode);
downgrade_write(&inode->i_rwsem);
}
/**
* nfs_end_io_read - declare that the buffered read operation is done
* @inode - file inode
*
* Declare that a buffered read operation is done, and release the shared
* lock on inode->i_rwsem.
*/
void
nfs_end_io_read(struct inode *inode)
{
up_read(&inode->i_rwsem);
}
/**
* nfs_start_io_write - declare the file is being used for buffered writes
* @inode - file inode
*
* Declare that a buffered read operation is about to start, and ensure
* that we block all direct I/O.
*/
void
nfs_start_io_write(struct inode *inode)
{
down_write(&inode->i_rwsem);
nfs_block_o_direct(NFS_I(inode), inode);
}
/**
* nfs_end_io_write - declare that the buffered write operation is done
* @inode - file inode
*
* Declare that a buffered write operation is done, and release the
* lock on inode->i_rwsem.
*/
void
nfs_end_io_write(struct inode *inode)
{
up_write(&inode->i_rwsem);
}
/* Call with exclusively locked inode->i_rwsem */
static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode)
{
if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
set_bit(NFS_INO_ODIRECT, &nfsi->flags);
nfs_wb_all(inode);
}
}
/**
* nfs_end_io_direct - declare the file is being used for direct i/o
* @inode - file inode
*
* Declare that a direct I/O operation is about to start, and ensure
* that we block all buffered I/O.
* On exit, the function ensures that the NFS_INO_ODIRECT flag is set,
* and holds a shared lock on inode->i_rwsem to ensure that the flag
* cannot be changed.
* In practice, this means that direct I/O operations are allowed to
* execute in parallel, thanks to the shared lock, whereas buffered I/O
* operations need to wait to grab an exclusive lock in order to clear
* NFS_INO_ODIRECT.
* Note that buffered writes and truncates both take a write lock on
* inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
*/
void
nfs_start_io_direct(struct inode *inode)
{
struct nfs_inode *nfsi = NFS_I(inode);
/* Be an optimist! */
down_read(&inode->i_rwsem);
if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0)
return;
up_read(&inode->i_rwsem);
/* Slow path.... */
down_write(&inode->i_rwsem);
nfs_block_buffered(nfsi, inode);
downgrade_write(&inode->i_rwsem);
}
/**
* nfs_end_io_direct - declare that the direct i/o operation is done
* @inode - file inode
*
* Declare that a direct I/O operation is done, and release the shared
* lock on inode->i_rwsem.
*/
void
nfs_end_io_direct(struct inode *inode)
{
up_read(&inode->i_rwsem);
}
......@@ -210,6 +210,7 @@ struct nfs_inode {
#define NFS_INO_LAYOUTCOMMIT (9) /* layoutcommit required */
#define NFS_INO_LAYOUTCOMMITTING (10) /* layoutcommit inflight */
#define NFS_INO_LAYOUTSTATS (11) /* layoutstats inflight */
#define NFS_INO_ODIRECT (12) /* I/O setting is O_DIRECT */
static inline struct nfs_inode *NFS_I(const struct inode *inode)
{
......
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