blob: e55723744f582991b9fdf75c77905bb4b0fa37ca [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* dax: direct host memory access
* Copyright (C) 2020 Red Hat, Inc.
*/
#include "fuse_i.h"
#include <linux/delay.h>
#include <linux/dax.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/pfn_t.h>
#include <linux/iomap.h>
#include <linux/interval_tree.h>
/*
* Default memory range size. A power of 2 so it agrees with common FUSE_INIT
* map_alignment values 4KB and 64KB.
*/
#define FUSE_DAX_SHIFT 21
#define FUSE_DAX_SZ (1 << FUSE_DAX_SHIFT)
#define FUSE_DAX_PAGES (FUSE_DAX_SZ / PAGE_SIZE)
/* Number of ranges reclaimer will try to free in one invocation */
#define FUSE_DAX_RECLAIM_CHUNK (10)
/*
* Dax memory reclaim threshold in percetage of total ranges. When free
* number of free ranges drops below this threshold, reclaim can trigger
* Default is 20%
*/
#define FUSE_DAX_RECLAIM_THRESHOLD (20)
/** Translation information for file offsets to DAX window offsets */
struct fuse_dax_mapping {
/* Pointer to inode where this memory range is mapped */
struct inode *inode;
/* Will connect in fcd->free_ranges to keep track of free memory */
struct list_head list;
/* For interval tree in file/inode */
struct interval_tree_node itn;
/* Will connect in fc->busy_ranges to keep track busy memory */
struct list_head busy_list;
/** Position in DAX window */
u64 window_offset;
/** Length of mapping, in bytes */
loff_t length;
/* Is this mapping read-only or read-write */
bool writable;
/* reference count when the mapping is used by dax iomap. */
refcount_t refcnt;
};
/* Per-inode dax map */
struct fuse_inode_dax {
/* Semaphore to protect modifications to the dmap tree */
struct rw_semaphore sem;
/* Sorted rb tree of struct fuse_dax_mapping elements */
struct rb_root_cached tree;
unsigned long nr;
};
struct fuse_conn_dax {
/* DAX device */
struct dax_device *dev;
/* Lock protecting accessess to members of this structure */
spinlock_t lock;
/* List of memory ranges which are busy */
unsigned long nr_busy_ranges;
struct list_head busy_ranges;
/* Worker to free up memory ranges */
struct delayed_work free_work;
/* Wait queue for a dax range to become free */
wait_queue_head_t range_waitq;
/* DAX Window Free Ranges */
long nr_free_ranges;
struct list_head free_ranges;
unsigned long nr_ranges;
};
static inline struct fuse_dax_mapping *
node_to_dmap(struct interval_tree_node *node)
{
if (!node)
return NULL;
return container_of(node, struct fuse_dax_mapping, itn);
}
static struct fuse_dax_mapping *
alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode);
static void
__kick_dmap_free_worker(struct fuse_conn_dax *fcd, unsigned long delay_ms)
{
unsigned long free_threshold;
/* If number of free ranges are below threshold, start reclaim */
free_threshold = max_t(unsigned long, fcd->nr_ranges * FUSE_DAX_RECLAIM_THRESHOLD / 100,
1);
if (fcd->nr_free_ranges < free_threshold)
queue_delayed_work(system_long_wq, &fcd->free_work,
msecs_to_jiffies(delay_ms));
}
static void kick_dmap_free_worker(struct fuse_conn_dax *fcd,
unsigned long delay_ms)
{
spin_lock(&fcd->lock);
__kick_dmap_free_worker(fcd, delay_ms);
spin_unlock(&fcd->lock);
}
static struct fuse_dax_mapping *alloc_dax_mapping(struct fuse_conn_dax *fcd)
{
struct fuse_dax_mapping *dmap;
spin_lock(&fcd->lock);
dmap = list_first_entry_or_null(&fcd->free_ranges,
struct fuse_dax_mapping, list);
if (dmap) {
list_del_init(&dmap->list);
WARN_ON(fcd->nr_free_ranges <= 0);
fcd->nr_free_ranges--;
}
spin_unlock(&fcd->lock);
kick_dmap_free_worker(fcd, 0);
return dmap;
}
/* This assumes fcd->lock is held */
static void __dmap_remove_busy_list(struct fuse_conn_dax *fcd,
struct fuse_dax_mapping *dmap)
{
list_del_init(&dmap->busy_list);
WARN_ON(fcd->nr_busy_ranges == 0);
fcd->nr_busy_ranges--;
}
static void dmap_remove_busy_list(struct fuse_conn_dax *fcd,
struct fuse_dax_mapping *dmap)
{
spin_lock(&fcd->lock);
__dmap_remove_busy_list(fcd, dmap);
spin_unlock(&fcd->lock);
}
/* This assumes fcd->lock is held */
static void __dmap_add_to_free_pool(struct fuse_conn_dax *fcd,
struct fuse_dax_mapping *dmap)
{
list_add_tail(&dmap->list, &fcd->free_ranges);
fcd->nr_free_ranges++;
wake_up(&fcd->range_waitq);
}
static void dmap_add_to_free_pool(struct fuse_conn_dax *fcd,
struct fuse_dax_mapping *dmap)
{
/* Return fuse_dax_mapping to free list */
spin_lock(&fcd->lock);
__dmap_add_to_free_pool(fcd, dmap);
spin_unlock(&fcd->lock);
}
static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
struct fuse_dax_mapping *dmap, bool writable,
bool upgrade)
{
struct fuse_mount *fm = get_fuse_mount(inode);
struct fuse_conn_dax *fcd = fm->fc->dax;
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_setupmapping_in inarg;
loff_t offset = start_idx << FUSE_DAX_SHIFT;
FUSE_ARGS(args);
ssize_t err;
WARN_ON(fcd->nr_free_ranges < 0);
/* Ask fuse daemon to setup mapping */
memset(&inarg, 0, sizeof(inarg));
inarg.foffset = offset;
inarg.fh = -1;
inarg.moffset = dmap->window_offset;
inarg.len = FUSE_DAX_SZ;
inarg.flags |= FUSE_SETUPMAPPING_FLAG_READ;
if (writable)
inarg.flags |= FUSE_SETUPMAPPING_FLAG_WRITE;
args.opcode = FUSE_SETUPMAPPING;
args.nodeid = fi->nodeid;
args.in_numargs = 1;
args.in_args[0].size = sizeof(inarg);
args.in_args[0].value = &inarg;
err = fuse_simple_request(fm, &args);
if (err < 0)
return err;
dmap->writable = writable;
if (!upgrade) {
/*
* We don't take a reference on inode. inode is valid right now
* and when inode is going away, cleanup logic should first
* cleanup dmap entries.
*/
dmap->inode = inode;
dmap->itn.start = dmap->itn.last = start_idx;
/* Protected by fi->dax->sem */
interval_tree_insert(&dmap->itn, &fi->dax->tree);
fi->dax->nr++;
spin_lock(&fcd->lock);
list_add_tail(&dmap->busy_list, &fcd->busy_ranges);
fcd->nr_busy_ranges++;
spin_unlock(&fcd->lock);
}
return 0;
}
static int fuse_send_removemapping(struct inode *inode,
struct fuse_removemapping_in *inargp,
struct fuse_removemapping_one *remove_one)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_mount *fm = get_fuse_mount(inode);
FUSE_ARGS(args);
args.opcode = FUSE_REMOVEMAPPING;
args.nodeid = fi->nodeid;
args.in_numargs = 2;
args.in_args[0].size = sizeof(*inargp);
args.in_args[0].value = inargp;
args.in_args[1].size = inargp->count * sizeof(*remove_one);
args.in_args[1].value = remove_one;
return fuse_simple_request(fm, &args);
}
static int dmap_removemapping_list(struct inode *inode, unsigned int num,
struct list_head *to_remove)
{
struct fuse_removemapping_one *remove_one, *ptr;
struct fuse_removemapping_in inarg;
struct fuse_dax_mapping *dmap;
int ret, i = 0, nr_alloc;
nr_alloc = min_t(unsigned int, num, FUSE_REMOVEMAPPING_MAX_ENTRY);
remove_one = kmalloc_array(nr_alloc, sizeof(*remove_one), GFP_NOFS);
if (!remove_one)
return -ENOMEM;
ptr = remove_one;
list_for_each_entry(dmap, to_remove, list) {
ptr->moffset = dmap->window_offset;
ptr->len = dmap->length;
ptr++;
i++;
num--;
if (i >= nr_alloc || num == 0) {
memset(&inarg, 0, sizeof(inarg));
inarg.count = i;
ret = fuse_send_removemapping(inode, &inarg,
remove_one);
if (ret)
goto out;
ptr = remove_one;
i = 0;
}
}
out:
kfree(remove_one);
return ret;
}
/*
* Cleanup dmap entry and add back to free list. This should be called with
* fcd->lock held.
*/
static void dmap_reinit_add_to_free_pool(struct fuse_conn_dax *fcd,
struct fuse_dax_mapping *dmap)
{
pr_debug("fuse: freeing memory range start_idx=0x%lx end_idx=0x%lx window_offset=0x%llx length=0x%llx\n",
dmap->itn.start, dmap->itn.last, dmap->window_offset,
dmap->length);
__dmap_remove_busy_list(fcd, dmap);
dmap->inode = NULL;
dmap->itn.start = dmap->itn.last = 0;
__dmap_add_to_free_pool(fcd, dmap);
}
/*
* Free inode dmap entries whose range falls inside [start, end].
* Does not take any locks. At this point of time it should only be
* called from evict_inode() path where we know all dmap entries can be
* reclaimed.
*/
static void inode_reclaim_dmap_range(struct fuse_conn_dax *fcd,
struct inode *inode,
loff_t start, loff_t end)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_dax_mapping *dmap, *n;
int err, num = 0;
LIST_HEAD(to_remove);
unsigned long start_idx = start >> FUSE_DAX_SHIFT;
unsigned long end_idx = end >> FUSE_DAX_SHIFT;
struct interval_tree_node *node;
while (1) {
node = interval_tree_iter_first(&fi->dax->tree, start_idx,
end_idx);
if (!node)
break;
dmap = node_to_dmap(node);
/* inode is going away. There should not be any users of dmap */
WARN_ON(refcount_read(&dmap->refcnt) > 1);
interval_tree_remove(&dmap->itn, &fi->dax->tree);
num++;
list_add(&dmap->list, &to_remove);
}
/* Nothing to remove */
if (list_empty(&to_remove))
return;
WARN_ON(fi->dax->nr < num);
fi->dax->nr -= num;
err = dmap_removemapping_list(inode, num, &to_remove);
if (err && err != -ENOTCONN) {
pr_warn("Failed to removemappings. start=0x%llx end=0x%llx\n",
start, end);
}
spin_lock(&fcd->lock);
list_for_each_entry_safe(dmap, n, &to_remove, list) {
list_del_init(&dmap->list);
dmap_reinit_add_to_free_pool(fcd, dmap);
}
spin_unlock(&fcd->lock);
}
static int dmap_removemapping_one(struct inode *inode,
struct fuse_dax_mapping *dmap)
{
struct fuse_removemapping_one forget_one;
struct fuse_removemapping_in inarg;
memset(&inarg, 0, sizeof(inarg));
inarg.count = 1;
memset(&forget_one, 0, sizeof(forget_one));
forget_one.moffset = dmap->window_offset;
forget_one.len = dmap->length;
return fuse_send_removemapping(inode, &inarg, &forget_one);
}
/*
* It is called from evict_inode() and by that time inode is going away. So
* this function does not take any locks like fi->dax->sem for traversing
* that fuse inode interval tree. If that lock is taken then lock validator
* complains of deadlock situation w.r.t fs_reclaim lock.
*/
void fuse_dax_inode_cleanup(struct inode *inode)
{
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_inode *fi = get_fuse_inode(inode);
/*
* fuse_evict_inode() has already called truncate_inode_pages_final()
* before we arrive here. So we should not have to worry about any
* pages/exception entries still associated with inode.
*/
inode_reclaim_dmap_range(fc->dax, inode, 0, -1);
WARN_ON(fi->dax->nr);
}
static void fuse_fill_iomap_hole(struct iomap *iomap, loff_t length)
{
iomap->addr = IOMAP_NULL_ADDR;
iomap->length = length;
iomap->type = IOMAP_HOLE;
}
static void fuse_fill_iomap(struct inode *inode, loff_t pos, loff_t length,
struct iomap *iomap, struct fuse_dax_mapping *dmap,
unsigned int flags)
{
loff_t offset, len;
loff_t i_size = i_size_read(inode);
offset = pos - (dmap->itn.start << FUSE_DAX_SHIFT);
len = min(length, dmap->length - offset);
/* If length is beyond end of file, truncate further */
if (pos + len > i_size)
len = i_size - pos;
if (len > 0) {
iomap->addr = dmap->window_offset + offset;
iomap->length = len;
if (flags & IOMAP_FAULT)
iomap->length = ALIGN(len, PAGE_SIZE);
iomap->type = IOMAP_MAPPED;
/*
* increace refcnt so that reclaim code knows this dmap is in
* use. This assumes fi->dax->sem mutex is held either
* shared/exclusive.
*/
refcount_inc(&dmap->refcnt);
/* iomap->private should be NULL */
WARN_ON_ONCE(iomap->private);
iomap->private = dmap;
} else {
/* Mapping beyond end of file is hole */
fuse_fill_iomap_hole(iomap, length);
}
}
static int fuse_setup_new_dax_mapping(struct inode *inode, loff_t pos,
loff_t length, unsigned int flags,
struct iomap *iomap)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_conn_dax *fcd = fc->dax;
struct fuse_dax_mapping *dmap, *alloc_dmap = NULL;
int ret;
bool writable = flags & IOMAP_WRITE;
unsigned long start_idx = pos >> FUSE_DAX_SHIFT;
struct interval_tree_node *node;
/*
* Can't do inline reclaim in fault path. We call
* dax_layout_busy_page() before we free a range. And
* fuse_wait_dax_page() drops fi->i_mmap_sem lock and requires it.
* In fault path we enter with fi->i_mmap_sem held and can't drop
* it. Also in fault path we hold fi->i_mmap_sem shared and not
* exclusive, so that creates further issues with fuse_wait_dax_page().
* Hence return -EAGAIN and fuse_dax_fault() will wait for a memory
* range to become free and retry.
*/
if (flags & IOMAP_FAULT) {
alloc_dmap = alloc_dax_mapping(fcd);
if (!alloc_dmap)
return -EAGAIN;
} else {
alloc_dmap = alloc_dax_mapping_reclaim(fcd, inode);
if (IS_ERR(alloc_dmap))
return PTR_ERR(alloc_dmap);
}
/* If we are here, we should have memory allocated */
if (WARN_ON(!alloc_dmap))
return -EIO;
/*
* Take write lock so that only one caller can try to setup mapping
* and other waits.
*/
down_write(&fi->dax->sem);
/*
* We dropped lock. Check again if somebody else setup
* mapping already.
*/
node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
if (node) {
dmap = node_to_dmap(node);
fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
dmap_add_to_free_pool(fcd, alloc_dmap);
up_write(&fi->dax->sem);
return 0;
}
/* Setup one mapping */
ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, alloc_dmap,
writable, false);
if (ret < 0) {
dmap_add_to_free_pool(fcd, alloc_dmap);
up_write(&fi->dax->sem);
return ret;
}
fuse_fill_iomap(inode, pos, length, iomap, alloc_dmap, flags);
up_write(&fi->dax->sem);
return 0;
}
static int fuse_upgrade_dax_mapping(struct inode *inode, loff_t pos,
loff_t length, unsigned int flags,
struct iomap *iomap)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_dax_mapping *dmap;
int ret;
unsigned long idx = pos >> FUSE_DAX_SHIFT;
struct interval_tree_node *node;
/*
* Take exclusive lock so that only one caller can try to setup
* mapping and others wait.
*/
down_write(&fi->dax->sem);
node = interval_tree_iter_first(&fi->dax->tree, idx, idx);
/* We are holding either inode lock or i_mmap_sem, and that should
* ensure that dmap can't be truncated. We are holding a reference
* on dmap and that should make sure it can't be reclaimed. So dmap
* should still be there in tree despite the fact we dropped and
* re-acquired the fi->dax->sem lock.
*/
ret = -EIO;
if (WARN_ON(!node))
goto out_err;
dmap = node_to_dmap(node);
/* We took an extra reference on dmap to make sure its not reclaimd.
* Now we hold fi->dax->sem lock and that reference is not needed
* anymore. Drop it.
*/
if (refcount_dec_and_test(&dmap->refcnt)) {
/* refcount should not hit 0. This object only goes
* away when fuse connection goes away
*/
WARN_ON_ONCE(1);
}
/* Maybe another thread already upgraded mapping while we were not
* holding lock.
*/
if (dmap->writable) {
ret = 0;
goto out_fill_iomap;
}
ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, dmap, true,
true);
if (ret < 0)
goto out_err;
out_fill_iomap:
fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
out_err:
up_write(&fi->dax->sem);
return ret;
}
/* This is just for DAX and the mapping is ephemeral, do not use it for other
* purposes since there is no block device with a permanent mapping.
*/
static int fuse_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
unsigned int flags, struct iomap *iomap,
struct iomap *srcmap)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_dax_mapping *dmap;
bool writable = flags & IOMAP_WRITE;
unsigned long start_idx = pos >> FUSE_DAX_SHIFT;
struct interval_tree_node *node;
/* We don't support FIEMAP */
if (WARN_ON(flags & IOMAP_REPORT))
return -EIO;
iomap->offset = pos;
iomap->flags = 0;
iomap->bdev = NULL;
iomap->dax_dev = fc->dax->dev;
/*
* Both read/write and mmap path can race here. So we need something
* to make sure if we are setting up mapping, then other path waits
*
* For now, use a semaphore for this. It probably needs to be
* optimized later.
*/
down_read(&fi->dax->sem);
node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
if (node) {
dmap = node_to_dmap(node);
if (writable && !dmap->writable) {
/* Upgrade read-only mapping to read-write. This will
* require exclusive fi->dax->sem lock as we don't want
* two threads to be trying to this simultaneously
* for same dmap. So drop shared lock and acquire
* exclusive lock.
*
* Before dropping fi->dax->sem lock, take reference
* on dmap so that its not freed by range reclaim.
*/
refcount_inc(&dmap->refcnt);
up_read(&fi->dax->sem);
pr_debug("%s: Upgrading mapping at offset 0x%llx length 0x%llx\n",
__func__, pos, length);
return fuse_upgrade_dax_mapping(inode, pos, length,
flags, iomap);
} else {
fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
up_read(&fi->dax->sem);
return 0;
}
} else {
up_read(&fi->dax->sem);
pr_debug("%s: no mapping at offset 0x%llx length 0x%llx\n",
__func__, pos, length);
if (pos >= i_size_read(inode))
goto iomap_hole;
return fuse_setup_new_dax_mapping(inode, pos, length, flags,
iomap);
}
/*
* If read beyond end of file happens, fs code seems to return
* it as hole
*/
iomap_hole:
fuse_fill_iomap_hole(iomap, length);
pr_debug("%s returning hole mapping. pos=0x%llx length_asked=0x%llx length_returned=0x%llx\n",
__func__, pos, length, iomap->length);
return 0;
}
static int fuse_iomap_end(struct inode *inode, loff_t pos, loff_t length,
ssize_t written, unsigned int flags,
struct iomap *iomap)
{
struct fuse_dax_mapping *dmap = iomap->private;
if (dmap) {
if (refcount_dec_and_test(&dmap->refcnt)) {
/* refcount should not hit 0. This object only goes
* away when fuse connection goes away
*/
WARN_ON_ONCE(1);
}
}
/* DAX writes beyond end-of-file aren't handled using iomap, so the
* file size is unchanged and there is nothing to do here.
*/
return 0;
}
static const struct iomap_ops fuse_iomap_ops = {
.iomap_begin = fuse_iomap_begin,
.iomap_end = fuse_iomap_end,
};
static void fuse_wait_dax_page(struct inode *inode)
{
struct fuse_inode *fi = get_fuse_inode(inode);
up_write(&fi->i_mmap_sem);
schedule();
down_write(&fi->i_mmap_sem);
}
/* Should be called with fi->i_mmap_sem lock held exclusively */
static int __fuse_dax_break_layouts(struct inode *inode, bool *retry,
loff_t start, loff_t end)
{
struct page *page;
page = dax_layout_busy_page_range(inode->i_mapping, start, end);
if (!page)
return 0;
*retry = true;
return ___wait_var_event(&page->_refcount,
atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
0, 0, fuse_wait_dax_page(inode));
}
/* dmap_end == 0 leads to unmapping of whole file */
int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start,
u64 dmap_end)
{
bool retry;
int ret;
do {
retry = false;
ret = __fuse_dax_break_layouts(inode, &retry, dmap_start,
dmap_end);
} while (ret == 0 && retry);
return ret;
}
ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
struct inode *inode = file_inode(iocb->ki_filp);
ssize_t ret;
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!inode_trylock_shared(inode))
return -EAGAIN;
} else {
inode_lock_shared(inode);
}
ret = dax_iomap_rw(iocb, to, &fuse_iomap_ops);
inode_unlock_shared(inode);
/* TODO file_accessed(iocb->f_filp) */
return ret;
}
static bool file_extending_write(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
return (iov_iter_rw(from) == WRITE &&
((iocb->ki_pos) >= i_size_read(inode) ||
(iocb->ki_pos + iov_iter_count(from) > i_size_read(inode))));
}
static ssize_t fuse_dax_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
ssize_t ret;
ret = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
if (ret < 0)
return ret;
fuse_invalidate_attr(inode);
fuse_write_update_size(inode, iocb->ki_pos);
return ret;
}
ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
ssize_t ret;
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!inode_trylock(inode))
return -EAGAIN;
} else {
inode_lock(inode);
}
ret = generic_write_checks(iocb, from);
if (ret <= 0)
goto out;
ret = file_remove_privs(iocb->ki_filp);
if (ret)
goto out;
/* TODO file_update_time() but we don't want metadata I/O */
/* Do not use dax for file extending writes as write and on
* disk i_size increase are not atomic otherwise.
*/
if (file_extending_write(iocb, from))
ret = fuse_dax_direct_write(iocb, from);
else
ret = dax_iomap_rw(iocb, from, &fuse_iomap_ops);
out:
inode_unlock(inode);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
return ret;
}
static int fuse_dax_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
struct fuse_conn *fc = get_fuse_conn(inode);
return dax_writeback_mapping_range(mapping, fc->dax->dev, wbc);
}
static vm_fault_t __fuse_dax_fault(struct vm_fault *vmf,
enum page_entry_size pe_size, bool write)
{
vm_fault_t ret;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct super_block *sb = inode->i_sb;
pfn_t pfn;
int error = 0;
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_conn_dax *fcd = fc->dax;
bool retry = false;
if (write)
sb_start_pagefault(sb);
retry:
if (retry && !(fcd->nr_free_ranges > 0))
wait_event(fcd->range_waitq, (fcd->nr_free_ranges > 0));
/*
* We need to serialize against not only truncate but also against
* fuse dax memory range reclaim. While a range is being reclaimed,
* we do not want any read/write/mmap to make progress and try
* to populate page cache or access memory we are trying to free.
*/
down_read(&get_fuse_inode(inode)->i_mmap_sem);
ret = dax_iomap_fault(vmf, pe_size, &pfn, &error, &fuse_iomap_ops);
if ((ret & VM_FAULT_ERROR) && error == -EAGAIN) {
error = 0;
retry = true;
up_read(&get_fuse_inode(inode)->i_mmap_sem);
goto retry;
}
if (ret & VM_FAULT_NEEDDSYNC)
ret = dax_finish_sync_fault(vmf, pe_size, pfn);
up_read(&get_fuse_inode(inode)->i_mmap_sem);
if (write)
sb_end_pagefault(sb);
return ret;
}
static vm_fault_t fuse_dax_fault(struct vm_fault *vmf)
{
return __fuse_dax_fault(vmf, PE_SIZE_PTE,
vmf->flags & FAULT_FLAG_WRITE);
}
static vm_fault_t fuse_dax_huge_fault(struct vm_fault *vmf,
enum page_entry_size pe_size)
{
return __fuse_dax_fault(vmf, pe_size, vmf->flags & FAULT_FLAG_WRITE);
}
static vm_fault_t fuse_dax_page_mkwrite(struct vm_fault *vmf)
{
return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
}
static vm_fault_t fuse_dax_pfn_mkwrite(struct vm_fault *vmf)
{
return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
}
static const struct vm_operations_struct fuse_dax_vm_ops = {
.fault = fuse_dax_fault,
.huge_fault = fuse_dax_huge_fault,
.page_mkwrite = fuse_dax_page_mkwrite,
.pfn_mkwrite = fuse_dax_pfn_mkwrite,
};
int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma)
{
file_accessed(file);
vma->vm_ops = &fuse_dax_vm_ops;
vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
return 0;
}
static int dmap_writeback_invalidate(struct inode *inode,
struct fuse_dax_mapping *dmap)
{
int ret;
loff_t start_pos = dmap->itn.start << FUSE_DAX_SHIFT;
loff_t end_pos = (start_pos + FUSE_DAX_SZ - 1);
ret = filemap_fdatawrite_range(inode->i_mapping, start_pos, end_pos);
if (ret) {
pr_debug("fuse: filemap_fdatawrite_range() failed. err=%d start_pos=0x%llx, end_pos=0x%llx\n",
ret, start_pos, end_pos);
return ret;
}
ret = invalidate_inode_pages2_range(inode->i_mapping,
start_pos >> PAGE_SHIFT,
end_pos >> PAGE_SHIFT);
if (ret)
pr_debug("fuse: invalidate_inode_pages2_range() failed err=%d\n",
ret);
return ret;
}
static int reclaim_one_dmap_locked(struct inode *inode,
struct fuse_dax_mapping *dmap)
{
int ret;
struct fuse_inode *fi = get_fuse_inode(inode);
/*
* igrab() was done to make sure inode won't go under us, and this
* further avoids the race with evict().
*/
ret = dmap_writeback_invalidate(inode, dmap);
if (ret)
return ret;
/* Remove dax mapping from inode interval tree now */
interval_tree_remove(&dmap->itn, &fi->dax->tree);
fi->dax->nr--;
/* It is possible that umount/shutdown has killed the fuse connection
* and worker thread is trying to reclaim memory in parallel. Don't
* warn in that case.
*/
ret = dmap_removemapping_one(inode, dmap);
if (ret && ret != -ENOTCONN) {
pr_warn("Failed to remove mapping. offset=0x%llx len=0x%llx ret=%d\n",
dmap->window_offset, dmap->length, ret);
}
return 0;
}
/* Find first mapped dmap for an inode and return file offset. Caller needs
* to hold fi->dax->sem lock either shared or exclusive.
*/
static struct fuse_dax_mapping *inode_lookup_first_dmap(struct inode *inode)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_dax_mapping *dmap;
struct interval_tree_node *node;
for (node = interval_tree_iter_first(&fi->dax->tree, 0, -1); node;
node = interval_tree_iter_next(node, 0, -1)) {
dmap = node_to_dmap(node);
/* still in use. */
if (refcount_read(&dmap->refcnt) > 1)
continue;
return dmap;
}
return NULL;
}
/*
* Find first mapping in the tree and free it and return it. Do not add
* it back to free pool.
*/
static struct fuse_dax_mapping *
inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
bool *retry)
{
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_dax_mapping *dmap;
u64 dmap_start, dmap_end;
unsigned long start_idx;
int ret;
struct interval_tree_node *node;
down_write(&fi->i_mmap_sem);
/* Lookup a dmap and corresponding file offset to reclaim. */
down_read(&fi->dax->sem);
dmap = inode_lookup_first_dmap(inode);
if (dmap) {
start_idx = dmap->itn.start;
dmap_start = start_idx << FUSE_DAX_SHIFT;
dmap_end = dmap_start + FUSE_DAX_SZ - 1;
}
up_read(&fi->dax->sem);
if (!dmap)
goto out_mmap_sem;
/*
* Make sure there are no references to inode pages using
* get_user_pages()
*/
ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end);
if (ret) {
pr_debug("fuse: fuse_dax_break_layouts() failed. err=%d\n",
ret);
dmap = ERR_PTR(ret);
goto out_mmap_sem;
}
down_write(&fi->dax->sem);
node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
/* Range already got reclaimed by somebody else */
if (!node) {
if (retry)
*retry = true;
goto out_write_dmap_sem;
}
dmap = node_to_dmap(node);
/* still in use. */
if (refcount_read(&dmap->refcnt) > 1) {
dmap = NULL;
if (retry)
*retry = true;
goto out_write_dmap_sem;
}
ret = reclaim_one_dmap_locked(inode, dmap);
if (ret < 0) {
dmap = ERR_PTR(ret);
goto out_write_dmap_sem;
}
/* Clean up dmap. Do not add back to free list */
dmap_remove_busy_list(fcd, dmap);
dmap->inode = NULL;
dmap->itn.start = dmap->itn.last = 0;
pr_debug("fuse: %s: inline reclaimed memory range. inode=%p, window_offset=0x%llx, length=0x%llx\n",
__func__, inode, dmap->window_offset, dmap->length);
out_write_dmap_sem:
up_write(&fi->dax->sem);
out_mmap_sem:
up_write(&fi->i_mmap_sem);
return dmap;
}
static struct fuse_dax_mapping *
alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode)
{
struct fuse_dax_mapping *dmap;
struct fuse_inode *fi = get_fuse_inode(inode);
while (1) {
bool retry = false;
dmap = alloc_dax_mapping(fcd);
if (dmap)
return dmap;
dmap = inode_inline_reclaim_one_dmap(fcd, inode, &retry);
/*
* Either we got a mapping or it is an error, return in both
* the cases.
*/
if (dmap)
return dmap;
/* If we could not reclaim a mapping because it
* had a reference or some other temporary failure,
* Try again. We want to give up inline reclaim only
* if there is no range assigned to this node. Otherwise
* if a deadlock is possible if we sleep with fi->i_mmap_sem
* held and worker to free memory can't make progress due
* to unavailability of fi->i_mmap_sem lock. So sleep
* only if fi->dax->nr=0
*/
if (retry)
continue;
/*
* There are no mappings which can be reclaimed. Wait for one.
* We are not holding fi->dax->sem. So it is possible
* that range gets added now. But as we are not holding
* fi->i_mmap_sem, worker should still be able to free up
* a range and wake us up.
*/
if (!fi->dax->nr && !(fcd->nr_free_ranges > 0)) {
if (wait_event_killable_exclusive(fcd->range_waitq,
(fcd->nr_free_ranges > 0))) {
return ERR_PTR(-EINTR);
}
}
}
}
static int lookup_and_reclaim_dmap_locked(struct fuse_conn_dax *fcd,
struct inode *inode,
unsigned long start_idx)
{
int ret;
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_dax_mapping *dmap;
struct interval_tree_node *node;
/* Find fuse dax mapping at file offset inode. */
node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
/* Range already got cleaned up by somebody else */
if (!node)
return 0;
dmap = node_to_dmap(node);
/* still in use. */
if (refcount_read(&dmap->refcnt) > 1)
return 0;
ret = reclaim_one_dmap_locked(inode, dmap);
if (ret < 0)
return ret;
/* Cleanup dmap entry and add back to free list */
spin_lock(&fcd->lock);
dmap_reinit_add_to_free_pool(fcd, dmap);
spin_unlock(&fcd->lock);
return ret;
}
/*
* Free a range of memory.
* Locking:
* 1. Take fi->i_mmap_sem to block dax faults.
* 2. Take fi->dax->sem to protect interval tree and also to make sure
* read/write can not reuse a dmap which we might be freeing.
*/
static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
struct inode *inode,
unsigned long start_idx,
unsigned long end_idx)
{
int ret;
struct fuse_inode *fi = get_fuse_inode(inode);
loff_t dmap_start = start_idx << FUSE_DAX_SHIFT;
loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1;
down_write(&fi->i_mmap_sem);
ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end);
if (ret) {
pr_debug("virtio_fs: fuse_dax_break_layouts() failed. err=%d\n",
ret);
goto out_mmap_sem;
}
down_write(&fi->dax->sem);
ret = lookup_and_reclaim_dmap_locked(fcd, inode, start_idx);
up_write(&fi->dax->sem);
out_mmap_sem:
up_write(&fi->i_mmap_sem);
return ret;
}
static int try_to_free_dmap_chunks(struct fuse_conn_dax *fcd,
unsigned long nr_to_free)
{
struct fuse_dax_mapping *dmap, *pos, *temp;
int ret, nr_freed = 0;
unsigned long start_idx = 0, end_idx = 0;
struct inode *inode = NULL;
/* Pick first busy range and free it for now*/
while (1) {
if (nr_freed >= nr_to_free)
break;
dmap = NULL;
spin_lock(&fcd->lock);
if (!fcd->nr_busy_ranges) {
spin_unlock(&fcd->lock);
return 0;
}
list_for_each_entry_safe(pos, temp, &fcd->busy_ranges,
busy_list) {
/* skip this range if it's in use. */
if (refcount_read(&pos->refcnt) > 1)
continue;
inode = igrab(pos->inode);
/*
* This inode is going away. That will free
* up all the ranges anyway, continue to
* next range.
*/
if (!inode)
continue;
/*
* Take this element off list and add it tail. If
* this element can't be freed, it will help with
* selecting new element in next iteration of loop.
*/
dmap = pos;
list_move_tail(&dmap->busy_list, &fcd->busy_ranges);
start_idx = end_idx = dmap->itn.start;
break;
}
spin_unlock(&fcd->lock);
if (!dmap)
return 0;
ret = lookup_and_reclaim_dmap(fcd, inode, start_idx, end_idx);
iput(inode);
if (ret)
return ret;
nr_freed++;
}
return 0;
}
static void fuse_dax_free_mem_worker(struct work_struct *work)
{
int ret;
struct fuse_conn_dax *fcd = container_of(work, struct fuse_conn_dax,
free_work.work);
ret = try_to_free_dmap_chunks(fcd, FUSE_DAX_RECLAIM_CHUNK);
if (ret) {
pr_debug("fuse: try_to_free_dmap_chunks() failed with err=%d\n",
ret);
}
/* If number of free ranges are still below threshold, requeue */
kick_dmap_free_worker(fcd, 1);
}
static void fuse_free_dax_mem_ranges(struct list_head *mem_list)
{
struct fuse_dax_mapping *range, *temp;
/* Free All allocated elements */
list_for_each_entry_safe(range, temp, mem_list, list) {
list_del(&range->list);
if (!list_empty(&range->busy_list))
list_del(&range->busy_list);
kfree(range);
}
}
void fuse_dax_conn_free(struct fuse_conn *fc)
{
if (fc->dax) {
fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
kfree(fc->dax);
}
}
static int fuse_dax_mem_range_init(struct fuse_conn_dax *fcd)
{
long nr_pages, nr_ranges;
void *kaddr;
pfn_t pfn;
struct fuse_dax_mapping *range;
int ret, id;
size_t dax_size = -1;
unsigned long i;
init_waitqueue_head(&fcd->range_waitq);
INIT_LIST_HEAD(&fcd->free_ranges);
INIT_LIST_HEAD(&fcd->busy_ranges);
INIT_DELAYED_WORK(&fcd->free_work, fuse_dax_free_mem_worker);
id = dax_read_lock();
nr_pages = dax_direct_access(fcd->dev, 0, PHYS_PFN(dax_size), &kaddr,
&pfn);
dax_read_unlock(id);
if (nr_pages < 0) {
pr_debug("dax_direct_access() returned %ld\n", nr_pages);
return nr_pages;
}
nr_ranges = nr_pages/FUSE_DAX_PAGES;
pr_debug("%s: dax mapped %ld pages. nr_ranges=%ld\n",
__func__, nr_pages, nr_ranges);
for (i = 0; i < nr_ranges; i++) {
range = kzalloc(sizeof(struct fuse_dax_mapping), GFP_KERNEL);
ret = -ENOMEM;
if (!range)
goto out_err;
/* TODO: This offset only works if virtio-fs driver is not
* having some memory hidden at the beginning. This needs
* better handling
*/
range->window_offset = i * FUSE_DAX_SZ;
range->length = FUSE_DAX_SZ;
INIT_LIST_HEAD(&range->busy_list);
refcount_set(&range->refcnt, 1);
list_add_tail(&range->list, &fcd->free_ranges);
}
fcd->nr_free_ranges = nr_ranges;
fcd->nr_ranges = nr_ranges;
return 0;
out_err:
/* Free All allocated elements */
fuse_free_dax_mem_ranges(&fcd->free_ranges);
return ret;
}
int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev)
{
struct fuse_conn_dax *fcd;
int err;
if (!dax_dev)
return 0;
fcd = kzalloc(sizeof(*fcd), GFP_KERNEL);
if (!fcd)
return -ENOMEM;
spin_lock_init(&fcd->lock);
fcd->dev = dax_dev;
err = fuse_dax_mem_range_init(fcd);
if (err) {
kfree(fcd);
return err;
}
fc->dax = fcd;
return 0;
}
bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi)
{
struct fuse_conn *fc = get_fuse_conn_super(sb);
fi->dax = NULL;
if (fc->dax) {
fi->dax = kzalloc(sizeof(*fi->dax), GFP_KERNEL_ACCOUNT);
if (!fi->dax)
return false;
init_rwsem(&fi->dax->sem);
fi->dax->tree = RB_ROOT_CACHED;
}
return true;
}
static const struct address_space_operations fuse_dax_file_aops = {
.writepages = fuse_dax_writepages,
.direct_IO = noop_direct_IO,
.set_page_dirty = __set_page_dirty_no_writeback,
.invalidatepage = noop_invalidatepage,
};
void fuse_dax_inode_init(struct inode *inode)
{
struct fuse_conn *fc = get_fuse_conn(inode);
if (!fc->dax)
return;
inode->i_flags |= S_DAX;
inode->i_data.a_ops = &fuse_dax_file_aops;
}
bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment)
{
if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) {
pr_warn("FUSE: map_alignment %u incompatible with dax mem range size %u\n",
map_alignment, FUSE_DAX_SZ);
return false;
}
return true;
}
void fuse_dax_cancel_work(struct fuse_conn *fc)
{
struct fuse_conn_dax *fcd = fc->dax;
if (fcd)
cancel_delayed_work_sync(&fcd->free_work);
}
EXPORT_SYMBOL_GPL(fuse_dax_cancel_work);