[PATCH 34/52] fuse: Add logic to free up a memory range

From: Vivek Goyal
Date: Mon Dec 10 2018 - 12:14:03 EST

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Add logic to free up a busy memory range. Freed memory range will be
returned to free pool. Add a worker which can be started to select
and free some busy memory ranges.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/fuse/file.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
fs/fuse/fuse_i.h | 10 ++++
fs/fuse/inode.c | 2 +
3 files changed, 159 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 73068289f62e..17becdff3014 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -272,7 +272,15 @@ static int fuse_setup_one_mapping(struct inode *inode,

pr_debug("fuse_setup_one_mapping() succeeded. offset=0x%llx err=%zd\n", offset, err);

- /* TODO: What locking is required here. For now, using fc->lock */
+ /*
+ * We don't take a refernce on inode. inode is valid right now and
+ * when inode is going away, cleanup logic should first cleanup
+ * dmap entries.
+ *
+ * TODO: Do we need to ensure that we are holding inode lock
+ * as well.
+ */
+ dmap->inode = inode;
dmap->start = offset;
dmap->end = offset + FUSE_DAX_MEM_RANGE_SZ - 1;
/* Protected by fi->i_dmap_sem */
@@ -347,6 +355,8 @@ void fuse_removemapping(struct inode *inode)
continue;
}

+ dmap->inode = NULL;
+
/* Add it back to free ranges list */
free_dax_mapping(fc, dmap);
}
@@ -3694,3 +3704,139 @@ void fuse_init_file_inode(struct inode *inode)
inode->i_data.a_ops = &fuse_dax_file_aops;
}
}
+
+int fuse_dax_free_one_mapping_locked(struct fuse_conn *fc, struct inode *inode,
+ u64 dmap_start)
+{
+ int ret;
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ struct fuse_dax_mapping *dmap;
+
+ WARN_ON(!inode_is_locked(inode));
+
+ /* Find fuse dax mapping at file offset inode. */
+ dmap = fuse_dax_interval_tree_iter_first(&fi->dmap_tree, dmap_start,
+ dmap_start);
+
+ /* Range already got cleaned up by somebody else */
+ if (!dmap)
+ return 0;
+
+ ret = filemap_fdatawrite_range(inode->i_mapping, dmap->start, dmap->end);
+ if (ret) {
+ printk("filemap_fdatawrite_range() failed. err=%d start=0x%llx,"
+ " end=0x%llx\n", ret, dmap->start, dmap->end);
+ return ret;
+ }
+
+ ret = invalidate_inode_pages2_range(inode->i_mapping,
+ dmap->start >> PAGE_SHIFT,
+ dmap->end >> PAGE_SHIFT);
+ /* TODO: What to do if above fails? For now,
+ * leave the range in place.
+ */
+ if (ret) {
+ printk("invalidate_inode_pages2_range() failed err=%d\n", ret);
+ return ret;
+ }
+
+ /* Remove dax mapping from inode interval tree now */
+ fuse_dax_interval_tree_remove(dmap, &fi->dmap_tree);
+ fi->nr_dmaps--;
+
+ /* Cleanup dmap entry and add back to free list */
+ spin_lock(&fc->lock);
+ list_del_init(&dmap->busy_list);
+ WARN_ON(fc->nr_busy_ranges == 0);
+ fc->nr_busy_ranges--;
+ dmap->inode = NULL;
+ dmap->start = dmap->end = 0;
+ __free_dax_mapping(fc, dmap);
+ spin_unlock(&fc->lock);
+
+ pr_debug("fuse: freed memory range window_offset=0x%llx,"
+ " length=0x%llx\n", dmap->window_offset,
+ dmap->length);
+
+ return ret;
+}
+
+/*
+ * Free a range of memory.
+ * Locking.
+ * 1. Take inode->i_rwsem to prever further read/write.
+ * 2. Take fuse_inode->i_mmap_sem to block dax faults.
+ * 3. Take fuse_inode->i_dmap_sem to protect interval tree. It might not
+ * be strictly necessary as lock 1 and 2 seem sufficient.
+ */
+int fuse_dax_free_one_mapping(struct fuse_conn *fc, struct inode *inode,
+ u64 dmap_start)
+{
+ int ret;
+ struct fuse_inode *fi = get_fuse_inode(inode);
+
+ inode_lock(inode);
+ down_write(&fi->i_mmap_sem);
+ down_write(&fi->i_dmap_sem);
+ ret = fuse_dax_free_one_mapping_locked(fc, inode, dmap_start);
+ up_write(&fi->i_dmap_sem);
+ up_write(&fi->i_mmap_sem);
+ inode_unlock(inode);
+ return ret;
+}
+
+int fuse_dax_free_memory(struct fuse_conn *fc, unsigned long nr_to_free)
+{
+ struct fuse_dax_mapping *dmap, *pos;
+ int ret, i;
+ u64 dmap_start = 0, window_offset = 0;
+ struct inode *inode = NULL;
+
+ /* Pick first busy range and free it for now*/
+ for (i = 0; i < nr_to_free; i++) {
+ dmap = NULL;
+ spin_lock(&fc->lock);
+
+ list_for_each_entry(pos, &fc->busy_ranges, busy_list) {
+ dmap = pos;
+ inode = igrab(dmap->inode);
+ /*
+ * This inode is going away. That will free
+ * up all the ranges anyway, continue to
+ * next range.
+ */
+ if (!inode)
+ continue;
+ dmap_start = dmap->start;
+ window_offset = dmap->window_offset;
+ break;
+ }
+ spin_unlock(&fc->lock);
+ if (!dmap)
+ return 0;
+
+ ret = fuse_dax_free_one_mapping(fc, inode, dmap_start);
+ iput(inode);
+ if (ret) {
+ printk("%s(window_offset=0x%llx) failed. err=%d\n",
+ __func__, window_offset, ret);
+ return ret;
+ }
+ }
+ return 0;
+}
+
+/* TODO: This probably should go in inode.c */
+void fuse_dax_free_mem_worker(struct work_struct *work)
+{
+ int ret;
+ struct fuse_conn *fc = container_of(work, struct fuse_conn,
+ dax_free_work.work);
+ pr_debug("fuse: Worker to free memory called.\n");
+ pr_debug("fuse: Worker to free memory called. nr_free_ranges=%lu"
+ " nr_busy_ranges=%lu\n", fc->nr_free_ranges,
+ fc->nr_busy_ranges);
+ ret = fuse_dax_free_memory(fc, FUSE_DAX_RECLAIM_CHUNK);
+ if (ret)
+ pr_debug("fuse: fuse_dax_free_memory() failed with err=%d\n", ret);
+}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 280f717deb57..383deaf0ecf1 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -50,6 +50,9 @@
#define FUSE_DAX_MEM_RANGE_SZ (2*1024*1024)
#define FUSE_DAX_MEM_RANGE_PAGES (FUSE_DAX_MEM_RANGE_SZ/PAGE_SIZE)

+/* Number of ranges reclaimer will try to free in one invocation */
+#define FUSE_DAX_RECLAIM_CHUNK (10)
+
/** List of active connections */
extern struct list_head fuse_conn_list;

@@ -102,6 +105,9 @@ struct fuse_forget_link {

/** 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 fc->free_ranges to keep track of free memory */
struct list_head list;

@@ -870,6 +876,9 @@ struct fuse_conn {
unsigned long nr_busy_ranges;
struct list_head busy_ranges;

+ /* Worker to free up memory ranges */
+ struct delayed_work dax_free_work;
+
/*
* DAX Window Free Ranges. TODO: This might not be best place to store
* this free list
@@ -1244,6 +1253,7 @@ unsigned fuse_len_args(unsigned numargs, struct fuse_arg *args);
* Get the next unique ID for a request
*/
u64 fuse_get_unique(struct fuse_iqueue *fiq);
+void fuse_dax_free_mem_worker(struct work_struct *work);
void fuse_removemapping(struct inode *inode);

#endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 59fc5a7a18fc..44f7bc44e319 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -713,6 +713,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
fc->user_ns = get_user_ns(user_ns);
INIT_LIST_HEAD(&fc->free_ranges);
INIT_LIST_HEAD(&fc->busy_ranges);
+ INIT_DELAYED_WORK(&fc->dax_free_work, fuse_dax_free_mem_worker);
}
EXPORT_SYMBOL_GPL(fuse_conn_init);

@@ -721,6 +722,7 @@ void fuse_conn_put(struct fuse_conn *fc)
if (refcount_dec_and_test(&fc->count)) {
if (fc->destroy_req)
fuse_request_free(fc->destroy_req);
+ flush_delayed_work(&fc->dax_free_work);
if (fc->dax_dev)
fuse_free_dax_mem_ranges(&fc->free_ranges);
put_pid_ns(fc->pid_ns);
--
2.13.6

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