linux/fs/fuse/control.c
NeilBrown 670d21c6e1 fuse: remove reliance on bdi congestion
The bdi congestion tracking in not widely used and will be removed.

Fuse is one of a small number of filesystems that uses it, setting both
the sync (read) and async (write) congestion flags at what it determines
are appropriate times.

The only remaining effect of the sync flag is to cause read-ahead to be
skipped.  The only remaining effect of the async flag is to cause (some)
WB_SYNC_NONE writes to be skipped.

So instead of setting the flags, change:

 - .readahead to stop when it has submitted all non-async pages for
   read.

 - .writepages to do nothing if WB_SYNC_NONE and the flag would be set

 - .writepage to return AOP_WRITEPAGE_ACTIVATE if WB_SYNC_NONE and the
   flag would be set.

The writepages change causes a behavioural change in that pageout() can
now return PAGE_ACTIVATE instead of PAGE_KEEP, so SetPageActive() will be
called on the page which (I think) will further delay the next attempt at
writeout.  This might be a good thing.

Link: https://lkml.kernel.org/r/164549983737.9187.2627117501000365074.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Paolo Valente <paolo.valente@linaro.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:00 -07:00

385 lines
8.5 KiB
C

/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2008 Miklos Szeredi <miklos@szeredi.hu>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
#include "fuse_i.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs_context.h>
#define FUSE_CTL_SUPER_MAGIC 0x65735543
/*
* This is non-NULL when the single instance of the control filesystem
* exists. Protected by fuse_mutex
*/
static struct super_block *fuse_control_sb;
static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
{
struct fuse_conn *fc;
mutex_lock(&fuse_mutex);
fc = file_inode(file)->i_private;
if (fc)
fc = fuse_conn_get(fc);
mutex_unlock(&fuse_mutex);
return fc;
}
static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
if (fc->abort_err)
fc->aborted = true;
fuse_abort_conn(fc);
fuse_conn_put(fc);
}
return count;
}
static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
char tmp[32];
size_t size;
if (!*ppos) {
long value;
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
value = atomic_read(&fc->num_waiting);
file->private_data = (void *)value;
fuse_conn_put(fc);
}
size = sprintf(tmp, "%ld\n", (long)file->private_data);
return simple_read_from_buffer(buf, len, ppos, tmp, size);
}
static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos, unsigned val)
{
char tmp[32];
size_t size = sprintf(tmp, "%u\n", val);
return simple_read_from_buffer(buf, len, ppos, tmp, size);
}
static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos, unsigned *val,
unsigned global_limit)
{
unsigned long t;
unsigned limit = (1 << 16) - 1;
int err;
if (*ppos)
return -EINVAL;
err = kstrtoul_from_user(buf, count, 0, &t);
if (err)
return err;
if (!capable(CAP_SYS_ADMIN))
limit = min(limit, global_limit);
if (t > limit)
return -EINVAL;
*val = t;
return count;
}
static ssize_t fuse_conn_max_background_read(struct file *file,
char __user *buf, size_t len,
loff_t *ppos)
{
struct fuse_conn *fc;
unsigned val;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
val = READ_ONCE(fc->max_background);
fuse_conn_put(fc);
return fuse_conn_limit_read(file, buf, len, ppos, val);
}
static ssize_t fuse_conn_max_background_write(struct file *file,
const char __user *buf,
size_t count, loff_t *ppos)
{
unsigned val;
ssize_t ret;
ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
max_user_bgreq);
if (ret > 0) {
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
spin_lock(&fc->bg_lock);
fc->max_background = val;
fc->blocked = fc->num_background >= fc->max_background;
if (!fc->blocked)
wake_up(&fc->blocked_waitq);
spin_unlock(&fc->bg_lock);
fuse_conn_put(fc);
}
}
return ret;
}
static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
char __user *buf, size_t len,
loff_t *ppos)
{
struct fuse_conn *fc;
unsigned val;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
val = READ_ONCE(fc->congestion_threshold);
fuse_conn_put(fc);
return fuse_conn_limit_read(file, buf, len, ppos, val);
}
static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
const char __user *buf,
size_t count, loff_t *ppos)
{
unsigned val;
struct fuse_conn *fc;
ssize_t ret;
ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
max_user_congthresh);
if (ret <= 0)
goto out;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
goto out;
down_read(&fc->killsb);
spin_lock(&fc->bg_lock);
fc->congestion_threshold = val;
spin_unlock(&fc->bg_lock);
up_read(&fc->killsb);
fuse_conn_put(fc);
out:
return ret;
}
static const struct file_operations fuse_ctl_abort_ops = {
.open = nonseekable_open,
.write = fuse_conn_abort_write,
.llseek = no_llseek,
};
static const struct file_operations fuse_ctl_waiting_ops = {
.open = nonseekable_open,
.read = fuse_conn_waiting_read,
.llseek = no_llseek,
};
static const struct file_operations fuse_conn_max_background_ops = {
.open = nonseekable_open,
.read = fuse_conn_max_background_read,
.write = fuse_conn_max_background_write,
.llseek = no_llseek,
};
static const struct file_operations fuse_conn_congestion_threshold_ops = {
.open = nonseekable_open,
.read = fuse_conn_congestion_threshold_read,
.write = fuse_conn_congestion_threshold_write,
.llseek = no_llseek,
};
static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
struct fuse_conn *fc,
const char *name,
int mode, int nlink,
const struct inode_operations *iop,
const struct file_operations *fop)
{
struct dentry *dentry;
struct inode *inode;
BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
dentry = d_alloc_name(parent, name);
if (!dentry)
return NULL;
inode = new_inode(fuse_control_sb);
if (!inode) {
dput(dentry);
return NULL;
}
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_uid = fc->user_id;
inode->i_gid = fc->group_id;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
/* setting ->i_op to NULL is not allowed */
if (iop)
inode->i_op = iop;
inode->i_fop = fop;
set_nlink(inode, nlink);
inode->i_private = fc;
d_add(dentry, inode);
fc->ctl_dentry[fc->ctl_ndents++] = dentry;
return dentry;
}
/*
* Add a connection to the control filesystem (if it exists). Caller
* must hold fuse_mutex
*/
int fuse_ctl_add_conn(struct fuse_conn *fc)
{
struct dentry *parent;
char name[32];
if (!fuse_control_sb)
return 0;
parent = fuse_control_sb->s_root;
inc_nlink(d_inode(parent));
sprintf(name, "%u", fc->dev);
parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
&simple_dir_inode_operations,
&simple_dir_operations);
if (!parent)
goto err;
if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
NULL, &fuse_ctl_waiting_ops) ||
!fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
NULL, &fuse_ctl_abort_ops) ||
!fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
1, NULL, &fuse_conn_max_background_ops) ||
!fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
S_IFREG | 0600, 1, NULL,
&fuse_conn_congestion_threshold_ops))
goto err;
return 0;
err:
fuse_ctl_remove_conn(fc);
return -ENOMEM;
}
/*
* Remove a connection from the control filesystem (if it exists).
* Caller must hold fuse_mutex
*/
void fuse_ctl_remove_conn(struct fuse_conn *fc)
{
int i;
if (!fuse_control_sb)
return;
for (i = fc->ctl_ndents - 1; i >= 0; i--) {
struct dentry *dentry = fc->ctl_dentry[i];
d_inode(dentry)->i_private = NULL;
if (!i) {
/* Get rid of submounts: */
d_invalidate(dentry);
}
dput(dentry);
}
drop_nlink(d_inode(fuse_control_sb->s_root));
}
static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
{
static const struct tree_descr empty_descr = {""};
struct fuse_conn *fc;
int err;
err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
if (err)
return err;
mutex_lock(&fuse_mutex);
BUG_ON(fuse_control_sb);
fuse_control_sb = sb;
list_for_each_entry(fc, &fuse_conn_list, entry) {
err = fuse_ctl_add_conn(fc);
if (err) {
fuse_control_sb = NULL;
mutex_unlock(&fuse_mutex);
return err;
}
}
mutex_unlock(&fuse_mutex);
return 0;
}
static int fuse_ctl_get_tree(struct fs_context *fsc)
{
return get_tree_single(fsc, fuse_ctl_fill_super);
}
static const struct fs_context_operations fuse_ctl_context_ops = {
.get_tree = fuse_ctl_get_tree,
};
static int fuse_ctl_init_fs_context(struct fs_context *fsc)
{
fsc->ops = &fuse_ctl_context_ops;
return 0;
}
static void fuse_ctl_kill_sb(struct super_block *sb)
{
struct fuse_conn *fc;
mutex_lock(&fuse_mutex);
fuse_control_sb = NULL;
list_for_each_entry(fc, &fuse_conn_list, entry)
fc->ctl_ndents = 0;
mutex_unlock(&fuse_mutex);
kill_litter_super(sb);
}
static struct file_system_type fuse_ctl_fs_type = {
.owner = THIS_MODULE,
.name = "fusectl",
.init_fs_context = fuse_ctl_init_fs_context,
.kill_sb = fuse_ctl_kill_sb,
};
MODULE_ALIAS_FS("fusectl");
int __init fuse_ctl_init(void)
{
return register_filesystem(&fuse_ctl_fs_type);
}
void __exit fuse_ctl_cleanup(void)
{
unregister_filesystem(&fuse_ctl_fs_type);
}