[PATCH 0/6] fuse: allocate req->pages[] dynamically

[PATCH 0/6] fuse: allocate req->pages[] dynamically

[Maxim Patlasov]

Hi,

Currently, any fuse request always includes inline pages[] array of
FUSE_MAX_PAGES_PER_REQ elements. This is the waste of memory because
in many cases smaller size would suffice.

The patch-set tries to allocate only as many elements of pages[] array as
actaully needed. This will be even more useful in the future because of:

1. Mitsuo's patches making maximum read/write request size tunable.
2. My patches optimizing scatter-gather direct IO. To make them simplier I'll
need to substitute array of 'struct page *' with array of 'struct bio_vec'.
It would make memory overhead worse if implemented w/o this patch-set.

Thanks,
Maxim

---

Maxim Patlasov (6):
      fuse: general infrastructure for pages[] of variable size
      fuse: categorize fuse_get_req()
      fuse: rework fuse_retrieve()
      fuse: rework fuse_readpages()
      fuse: rework fuse_perform_write()
      fuse: rework fuse_do_ioctl()


 fs/fuse/cuse.c   |    2 +-
 fs/fuse/dev.c    |   70 +++++++++++++++++++++++++++++++++++++-----------------
 fs/fuse/dir.c    |   38 +++++++++++++++--------------
 fs/fuse/file.c   |   53 +++++++++++++++++++++++++----------------
 fs/fuse/fuse_i.h |   45 ++++++++++++++++++++++++++++++-----
 fs/fuse/inode.c  |    6 ++---
 6 files changed, 143 insertions(+), 71 deletions(-)

-- 
Signature

[PATCH 1/6] fuse: general infrastructure for pages[] of variable size

[Maxim Patlasov]

The patch removes inline array of FUSE_MAX_PAGES_PER_REQ page pointers from
fuse_req. Instead of that, req->pages may now point either to small inline
array or to an array allocated dynamically.

This essentially means that all callers of fuse_request_alloc[_nofs] should
pass the number of pages needed explicitly.

The patch doesn't make any logic changes.
---
 fs/fuse/dev.c    |   40 ++++++++++++++++++++++++++++++----------
 fs/fuse/file.c   |    4 ++--
 fs/fuse/fuse_i.h |    9 ++++++---
 fs/fuse/inode.c  |    4 ++--
 4 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 7df2b5e..c0283a1 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -36,32 +36,52 @@ static struct fuse_conn *fuse_get_conn(struct file *file)
 
 static void fuse_request_init(struct fuse_req *req)
 {
+	struct page **pages = req->pages;
+
 	memset(req, 0, sizeof(*req));
 	INIT_LIST_HEAD(&req->list);
 	INIT_LIST_HEAD(&req->intr_entry);
 	init_waitqueue_head(&req->waitq);
 	atomic_set(&req->count, 1);
+
+	req->pages = pages;
 }
 
-struct fuse_req *fuse_request_alloc(void)
+static struct fuse_req *__fuse_request_alloc(int npages, gfp_t flags)
 {
-	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_KERNEL);
-	if (req)
+	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, flags);
+	if (req) {
+		if (npages <= 1)
+			req->pages = req->inline_pages;
+		else
+			req->pages = kmalloc(sizeof(struct page *) * npages,
+					     flags);
+
+		if (!req->pages) {
+			kmem_cache_free(fuse_req_cachep, req);
+			return NULL;
+		}
+
 		fuse_request_init(req);
+	}
 	return req;
 }
+
+struct fuse_req *fuse_request_alloc(int npages)
+{
+	return __fuse_request_alloc(npages, GFP_KERNEL);
+}
 EXPORT_SYMBOL_GPL(fuse_request_alloc);
 
-struct fuse_req *fuse_request_alloc_nofs(void)
+struct fuse_req *fuse_request_alloc_nofs(int npages)
 {
-	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_NOFS);
-	if (req)
-		fuse_request_init(req);
-	return req;
+	return __fuse_request_alloc(npages, GFP_NOFS);
 }
 
 void fuse_request_free(struct fuse_req *req)
 {
+	if (req->pages != req->inline_pages)
+		kfree(req->pages);
 	kmem_cache_free(fuse_req_cachep, req);
 }
 
@@ -116,7 +136,7 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc)
 	if (!fc->connected)
 		goto out;
 
-	req = fuse_request_alloc();
+	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
 	err = -ENOMEM;
 	if (!req)
 		goto out;
@@ -193,7 +213,7 @@ struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
 
 	atomic_inc(&fc->num_waiting);
 	wait_event(fc->blocked_waitq, !fc->blocked);
-	req = fuse_request_alloc();
+	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
 	if (!req)
 		req = get_reserved_req(fc, file);
 
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index aba15f1..7423ea4 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -57,7 +57,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
 		return NULL;
 
 	ff->fc = fc;
-	ff->reserved_req = fuse_request_alloc();
+	ff->reserved_req = fuse_request_alloc(0);
 	if (unlikely(!ff->reserved_req)) {
 		kfree(ff);
 		return NULL;
@@ -1272,7 +1272,7 @@ static int fuse_writepage_locked(struct page *page)
 
 	set_page_writeback(page);
 
-	req = fuse_request_alloc_nofs();
+	req = fuse_request_alloc_nofs(1);
 	if (!req)
 		goto err;
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e24dd74..5e78840 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -291,7 +291,10 @@ struct fuse_req {
 	} misc;
 
 	/** page vector */
-	struct page *pages[FUSE_MAX_PAGES_PER_REQ];
+	struct page **pages;
+
+	/** inline page vector */
+	struct page *inline_pages[1];
 
 	/** number of pages in vector */
 	unsigned num_pages;
@@ -658,9 +661,9 @@ void fuse_ctl_cleanup(void);
 /**
  * Allocate a request
  */
-struct fuse_req *fuse_request_alloc(void);
+struct fuse_req *fuse_request_alloc(int npages);
 
-struct fuse_req *fuse_request_alloc_nofs(void);
+struct fuse_req *fuse_request_alloc_nofs(int npages);
 
 /**
  * Free a request
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index ce0a283..3f399ba 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1027,12 +1027,12 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	/* only now - we want root dentry with NULL ->d_op */
 	sb->s_d_op = &fuse_dentry_operations;
 
-	init_req = fuse_request_alloc();
+	init_req = fuse_request_alloc(0);
 	if (!init_req)
 		goto err_put_root;
 
 	if (is_bdev) {
-		fc->destroy_req = fuse_request_alloc();
+		fc->destroy_req = fuse_request_alloc(0);
 		if (!fc->destroy_req)
 			goto err_free_init_req;
 	}

Re: [PATCH 1/6] fuse: general infrastructure for pages[] of variable size

[Miklos Szeredi]

Maxim Patlasov <mpatlasov@parallels.com> writes:

> The patch removes inline array of FUSE_MAX_PAGES_PER_REQ page pointers from
> fuse_req. Instead of that, req->pages may now point either to small inline
> array or to an array allocated dynamically.
>
> This essentially means that all callers of fuse_request_alloc[_nofs] should
> pass the number of pages needed explicitly.
>
> The patch doesn't make any logic changes.

See comments inline.


> ---
>  fs/fuse/dev.c    |   40 ++++++++++++++++++++++++++++++----------
>  fs/fuse/file.c   |    4 ++--
>  fs/fuse/fuse_i.h |    9 ++++++---
>  fs/fuse/inode.c  |    4 ++--
>  4 files changed, 40 insertions(+), 17 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 7df2b5e..c0283a1 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -36,32 +36,52 @@ static struct fuse_conn *fuse_get_conn(struct file *file)
>  
>  static void fuse_request_init(struct fuse_req *req)
>  {
> +	struct page **pages = req->pages;
> +

Rather than this, make fuse_request_init() take 'pages' as a second
argument.

>  	memset(req, 0, sizeof(*req));
>  	INIT_LIST_HEAD(&req->list);
>  	INIT_LIST_HEAD(&req->intr_entry);
>  	init_waitqueue_head(&req->waitq);
>  	atomic_set(&req->count, 1);
> +
> +	req->pages = pages;
>  }
>  
> -struct fuse_req *fuse_request_alloc(void)
> +static struct fuse_req *__fuse_request_alloc(int npages, gfp_t flags)
>  {
> -	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_KERNEL);
> -	if (req)
> +	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, flags);
> +	if (req) {
> +		if (npages <= 1)

Instead of '1' use a constant (e.g. FUSE_REQ_INLINE_PAGES)

> +			req->pages = req->inline_pages;
> +		else
> +			req->pages = kmalloc(sizeof(struct page *) * npages,
> +					     flags);
> +
> +		if (!req->pages) {
> +			kmem_cache_free(fuse_req_cachep, req);
> +			return NULL;
> +		}
> +
>  		fuse_request_init(req);
> +	}
>  	return req;
>  }
> +
> +struct fuse_req *fuse_request_alloc(int npages)
> +{
> +	return __fuse_request_alloc(npages, GFP_KERNEL);
> +}
>  EXPORT_SYMBOL_GPL(fuse_request_alloc);
>  
> -struct fuse_req *fuse_request_alloc_nofs(void)
> +struct fuse_req *fuse_request_alloc_nofs(int npages)
>  {
> -	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_NOFS);
> -	if (req)
> -		fuse_request_init(req);
> -	return req;
> +	return __fuse_request_alloc(npages, GFP_NOFS);
>  }
>  
>  void fuse_request_free(struct fuse_req *req)
>  {
> +	if (req->pages != req->inline_pages)
> +		kfree(req->pages);
>  	kmem_cache_free(fuse_req_cachep, req);
>  }
>  
> @@ -116,7 +136,7 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc)
>  	if (!fc->connected)
>  		goto out;
>  
> -	req = fuse_request_alloc();
> +	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
>  	err = -ENOMEM;
>  	if (!req)
>  		goto out;
> @@ -193,7 +213,7 @@ struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
>  
>  	atomic_inc(&fc->num_waiting);
>  	wait_event(fc->blocked_waitq, !fc->blocked);
> -	req = fuse_request_alloc();
> +	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
>  	if (!req)
>  		req = get_reserved_req(fc, file);
>  
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index aba15f1..7423ea4 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -57,7 +57,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
>  		return NULL;
>  
>  	ff->fc = fc;
> -	ff->reserved_req = fuse_request_alloc();
> +	ff->reserved_req = fuse_request_alloc(0);
>  	if (unlikely(!ff->reserved_req)) {
>  		kfree(ff);
>  		return NULL;
> @@ -1272,7 +1272,7 @@ static int fuse_writepage_locked(struct page *page)
>  
>  	set_page_writeback(page);
>  
> -	req = fuse_request_alloc_nofs();
> +	req = fuse_request_alloc_nofs(1);
>  	if (!req)
>  		goto err;
>  
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index e24dd74..5e78840 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -291,7 +291,10 @@ struct fuse_req {
>  	} misc;
>  
>  	/** page vector */
> -	struct page *pages[FUSE_MAX_PAGES_PER_REQ];
> +	struct page **pages;
> +
> +	/** inline page vector */
> +	struct page *inline_pages[1];
>  

To defend against programming errors, I think it would be wise to add

	/** size of the 'pages' array */
	unsigned max_pages;

so that when storing pages in the array we can check whether we are
overflowing the array.

>  	/** number of pages in vector */
>  	unsigned num_pages;
> @@ -658,9 +661,9 @@ void fuse_ctl_cleanup(void);
>  /**
>   * Allocate a request
>   */
> -struct fuse_req *fuse_request_alloc(void);
> +struct fuse_req *fuse_request_alloc(int npages);
>  
> -struct fuse_req *fuse_request_alloc_nofs(void);
> +struct fuse_req *fuse_request_alloc_nofs(int npages);
>  
>  /**
>   * Free a request
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index ce0a283..3f399ba 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1027,12 +1027,12 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
>  	/* only now - we want root dentry with NULL ->d_op */
>  	sb->s_d_op = &fuse_dentry_operations;
>  
> -	init_req = fuse_request_alloc();
> +	init_req = fuse_request_alloc(0);
>  	if (!init_req)
>  		goto err_put_root;
>  
>  	if (is_bdev) {
> -		fc->destroy_req = fuse_request_alloc();
> +		fc->destroy_req = fuse_request_alloc(0);
>  		if (!fc->destroy_req)
>  			goto err_free_init_req;
>  	}

[PATCH 2/6] fuse: categorize fuse_get_req()

[Maxim Patlasov]

The patch categorizes all fuse_get_req() invocations into three categories:
 - fuse_get_req_nopages() - when caller doesn't care about req->pages
 - fuse_get_req_onepage() - when caller need exactly one page
 - fuse_get_req_multipage() - in other cases.

The decision to split one fuse_get_req() into three different functions was
made because having fuse_get_req(fc, n) scattered over code would be too error
prone. After splitting, it's clear from the first glance when a caller needs
multi-page fuse_req.

The patch doesn't make any logic changes. In multi-page case, it silly
allocates array of FUSE_MAX_PAGES_PER_REQ page pointers. This will be amended
by future patches.
---
 fs/fuse/cuse.c   |    2 +-
 fs/fuse/dev.c    |   10 +++++-----
 fs/fuse/dir.c    |   38 +++++++++++++++++++-------------------
 fs/fuse/file.c   |   30 +++++++++++++++---------------
 fs/fuse/fuse_i.h |   36 +++++++++++++++++++++++++++++++++---
 fs/fuse/inode.c  |    2 +-
 6 files changed, 74 insertions(+), 44 deletions(-)

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 3426521..672d86a 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -411,7 +411,7 @@ static int cuse_send_init(struct cuse_conn *cc)
 
 	BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_onepage(fc);
 	if (IS_ERR(req)) {
 		rc = PTR_ERR(req);
 		goto err;
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index c0283a1..6e38af5 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -117,7 +117,7 @@ static void fuse_req_init_context(struct fuse_req *req)
 	req->in.h.pid = current->pid;
 }
 
-struct fuse_req *fuse_get_req(struct fuse_conn *fc)
+struct fuse_req *fuse_get_req(struct fuse_conn *fc, int npages)
 {
 	struct fuse_req *req;
 	sigset_t oldset;
@@ -136,7 +136,7 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc)
 	if (!fc->connected)
 		goto out;
 
-	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
+	req = fuse_request_alloc(npages);
 	err = -ENOMEM;
 	if (!req)
 		goto out;
@@ -207,13 +207,13 @@ static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
  * filesystem should not have it's own file open.  If deadlock is
  * intentional, it can still be broken by "aborting" the filesystem.
  */
-struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
+struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc, struct file *file)
 {
 	struct fuse_req *req;
 
 	atomic_inc(&fc->num_waiting);
 	wait_event(fc->blocked_waitq, !fc->blocked);
-	req = fuse_request_alloc(FUSE_MAX_PAGES_PER_REQ);
+	req = fuse_request_alloc(0);
 	if (!req)
 		req = get_reserved_req(fc, file);
 
@@ -1563,7 +1563,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 	unsigned int offset;
 	size_t total_len = 0;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 324bc08..ff7af98 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -178,7 +178,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 			return -ECHILD;
 
 		fc = get_fuse_conn(inode);
-		req = fuse_get_req(fc);
+		req = fuse_get_req_nopages(fc);
 		if (IS_ERR(req))
 			return 0;
 
@@ -271,7 +271,7 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
 	if (name->len > FUSE_NAME_MAX)
 		goto out;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	err = PTR_ERR(req);
 	if (IS_ERR(req))
 		goto out;
@@ -391,7 +391,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	if (!forget)
 		goto out_err;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	err = PTR_ERR(req);
 	if (IS_ERR(req))
 		goto out_put_forget_req;
@@ -592,7 +592,7 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
 {
 	struct fuse_mknod_in inarg;
 	struct fuse_conn *fc = get_fuse_conn(dir);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -623,7 +623,7 @@ static int fuse_mkdir(struct inode *dir, struct dentry *entry, umode_t mode)
 {
 	struct fuse_mkdir_in inarg;
 	struct fuse_conn *fc = get_fuse_conn(dir);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -647,7 +647,7 @@ static int fuse_symlink(struct inode *dir, struct dentry *entry,
 {
 	struct fuse_conn *fc = get_fuse_conn(dir);
 	unsigned len = strlen(link) + 1;
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -664,7 +664,7 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)
 {
 	int err;
 	struct fuse_conn *fc = get_fuse_conn(dir);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -696,7 +696,7 @@ static int fuse_rmdir(struct inode *dir, struct dentry *entry)
 {
 	int err;
 	struct fuse_conn *fc = get_fuse_conn(dir);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -723,7 +723,7 @@ static int fuse_rename(struct inode *olddir, struct dentry *oldent,
 	int err;
 	struct fuse_rename_in inarg;
 	struct fuse_conn *fc = get_fuse_conn(olddir);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 
 	if (IS_ERR(req))
 		return PTR_ERR(req);
@@ -776,7 +776,7 @@ static int fuse_link(struct dentry *entry, struct inode *newdir,
 	struct fuse_link_in inarg;
 	struct inode *inode = entry->d_inode;
 	struct fuse_conn *fc = get_fuse_conn(inode);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -848,7 +848,7 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
 	struct fuse_req *req;
 	u64 attr_version;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1029,7 +1029,7 @@ static int fuse_access(struct inode *inode, int mask)
 	if (fc->no_access)
 		return 0;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1167,7 +1167,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
 	if (is_bad_inode(inode))
 		return -EIO;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_onepage(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1197,7 +1197,7 @@ static char *read_link(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
 	struct fuse_conn *fc = get_fuse_conn(inode);
-	struct fuse_req *req = fuse_get_req(fc);
+	struct fuse_req *req = fuse_get_req_nopages(fc);
 	char *link;
 
 	if (IS_ERR(req))
@@ -1410,7 +1410,7 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
 	if (attr->ia_valid & ATTR_SIZE)
 		is_truncate = true;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1518,7 +1518,7 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 	if (fc->no_setxattr)
 		return -EOPNOTSUPP;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1557,7 +1557,7 @@ static ssize_t fuse_getxattr(struct dentry *entry, const char *name,
 	if (fc->no_getxattr)
 		return -EOPNOTSUPP;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1609,7 +1609,7 @@ static ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size)
 	if (fc->no_listxattr)
 		return -EOPNOTSUPP;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1654,7 +1654,7 @@ static int fuse_removexattr(struct dentry *entry, const char *name)
 	if (fc->no_removexattr)
 		return -EOPNOTSUPP;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 7423ea4..c811f3d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -25,7 +25,7 @@ static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
 	struct fuse_req *req;
 	int err;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -368,7 +368,7 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (fc->no_flush)
 		return 0;
 
-	req = fuse_get_req_nofail(fc, file);
+	req = fuse_get_req_nofail_nopages(fc, file);
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;
 	inarg.lock_owner = fuse_lock_owner_id(fc, id);
@@ -436,7 +436,7 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
 
 	fuse_sync_writes(inode);
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		goto out;
@@ -544,7 +544,7 @@ static int fuse_readpage(struct file *file, struct page *page)
 	 */
 	fuse_wait_on_page_writeback(inode, page->index);
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_onepage(fc);
 	err = PTR_ERR(req);
 	if (IS_ERR(req))
 		goto out;
@@ -657,7 +657,7 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 	     (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
 	     req->pages[req->num_pages - 1]->index + 1 != page->index)) {
 		fuse_send_readpages(req, data->file);
-		data->req = req = fuse_get_req(fc);
+		data->req = req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 		if (IS_ERR(req)) {
 			unlock_page(page);
 			return PTR_ERR(req);
@@ -683,7 +683,7 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 
 	data.file = file;
 	data.inode = inode;
-	data.req = fuse_get_req(fc);
+	data.req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 	err = PTR_ERR(data.req);
 	if (IS_ERR(data.req))
 		goto out;
@@ -890,7 +890,7 @@ static ssize_t fuse_perform_write(struct file *file,
 		struct fuse_req *req;
 		ssize_t count;
 
-		req = fuse_get_req(fc);
+		req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 		if (IS_ERR(req)) {
 			err = PTR_ERR(req);
 			break;
@@ -1072,7 +1072,7 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
 	ssize_t res = 0;
 	struct fuse_req *req;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1108,7 +1108,7 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
 			break;
 		if (count) {
 			fuse_put_request(fc, req);
-			req = fuse_get_req(fc);
+			req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 			if (IS_ERR(req))
 				break;
 		}
@@ -1470,7 +1470,7 @@ static int fuse_getlk(struct file *file, struct file_lock *fl)
 	struct fuse_lk_out outarg;
 	int err;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1505,7 +1505,7 @@ static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
 	if (fl->fl_flags & FL_CLOSE)
 		return 0;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -1574,7 +1574,7 @@ static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
 	if (!inode->i_sb->s_bdev || fc->no_bmap)
 		return 0;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return 0;
 
@@ -1872,7 +1872,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
 		num_pages++;
 	}
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		req = NULL;
@@ -2075,7 +2075,7 @@ unsigned fuse_file_poll(struct file *file, poll_table *wait)
 		fuse_register_polled_file(fc, ff);
 	}
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return POLLERR;
 
@@ -2193,7 +2193,7 @@ long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 	if (fc->no_fallocate)
 		return -EOPNOTSUPP;
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5e78840..f41b149 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -671,14 +671,44 @@ struct fuse_req *fuse_request_alloc_nofs(int npages);
 void fuse_request_free(struct fuse_req *req);
 
 /**
- * Get a request, may fail with -ENOMEM
+ * Get a request, may fail with -ENOMEM,
+ * caller should specify # elements in req->pages[] explicitly
  */
-struct fuse_req *fuse_get_req(struct fuse_conn *fc);
+struct fuse_req *fuse_get_req(struct fuse_conn *fc, int npages);
+
+/**
+ * Get a request, may fail with -ENOMEM,
+ * useful for callers who doesn't use req->pages[]
+ */
+static inline struct fuse_req *fuse_get_req_nopages(struct fuse_conn *fc)
+{
+	return fuse_get_req(fc, 0);
+}
+
+/**
+ * Get a request, may fail with -ENOMEM,
+ * useful for callers who need only one page in req->pages[]
+ */
+static inline struct fuse_req *fuse_get_req_onepage(struct fuse_conn *fc)
+{
+	return fuse_get_req(fc, 1);
+}
+
+/**
+ * Get a request, may fail with -ENOMEM,
+ * useful for callers who need many pages in req->pages[]
+ */
+static inline struct fuse_req *fuse_get_req_multipage(struct fuse_conn *fc,
+						      int n)
+{
+	return fuse_get_req(fc, n);
+}
 
 /**
  * Gets a requests for a file operation, always succeeds
  */
-struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file);
+struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
+					     struct file *file);
 
 /**
  * Decrement reference count of a request.  If count goes to zero free
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 3f399ba..efb6144 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -411,7 +411,7 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 		return 0;
 	}
 
-	req = fuse_get_req(fc);
+	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 

Re: [PATCH 2/6] fuse: categorize fuse_get_req()

[Miklos Szeredi]

Maxim Patlasov <mpatlasov@parallels.com> writes:

> The patch categorizes all fuse_get_req() invocations into three categories:
>  - fuse_get_req_nopages() - when caller doesn't care about req->pages
>  - fuse_get_req_onepage() - when caller need exactly one page
>  - fuse_get_req_multipage() - in other cases.

I think you are overcomplicating this.

Just have two functions: fuse_get_req_nopages() and fuse_get_req().

I don't think the _onepage variant deserves a separate helper.

Thanks,
Miklos

[PATCH 3/6] fuse: rework fuse_retrieve()

[Maxim Patlasov]

The patch reworks fuse_retrieve() to allocate only so many page pointers
as needed. The core part of the patch is the following calculation:

	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

(thanks Miklos for formula). All other changes are moslty shuffling lines.

The patch also contains one-line fix suggested by Miklos: the loop iterating
over pages from inode mapping should interpret 'offset' as offset in the very
first page only.
---
 fs/fuse/dev.c |   26 ++++++++++++++++----------
 1 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6e38af5..cf69df3 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1562,13 +1562,24 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 	unsigned int num;
 	unsigned int offset;
 	size_t total_len = 0;
+	int num_pages;
 
-	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
+	offset = outarg->offset & ~PAGE_CACHE_MASK;
+	file_size = i_size_read(inode);
+
+	num = outarg->size;
+	if (outarg->offset > file_size)
+		num = 0;
+	else if (outarg->offset + num > file_size)
+		num = file_size - outarg->offset;
+
+	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	num_pages = min(num_pages, FUSE_MAX_PAGES_PER_REQ);
+
+	req = fuse_get_req_multipage(fc, num_pages);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
-	offset = outarg->offset & ~PAGE_CACHE_MASK;
-
 	req->in.h.opcode = FUSE_NOTIFY_REPLY;
 	req->in.h.nodeid = outarg->nodeid;
 	req->in.numargs = 2;
@@ -1577,14 +1588,8 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 	req->end = fuse_retrieve_end;
 
 	index = outarg->offset >> PAGE_CACHE_SHIFT;
-	file_size = i_size_read(inode);
-	num = outarg->size;
-	if (outarg->offset > file_size)
-		num = 0;
-	else if (outarg->offset + num > file_size)
-		num = file_size - outarg->offset;
 
-	while (num && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
+	while (num && req->num_pages < num_pages) {
 		struct page *page;
 		unsigned int this_num;
 
@@ -1596,6 +1601,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
 		req->pages[req->num_pages] = page;
 		req->num_pages++;
 
+		offset = 0;
 		num -= this_num;
 		total_len += this_num;
 		index++;

Re: [PATCH 3/6] fuse: rework fuse_retrieve()

[Miklos Szeredi]

Maxim Patlasov <mpatlasov@parallels.com> writes:

> The patch reworks fuse_retrieve() to allocate only so many page pointers
> as needed. The core part of the patch is the following calculation:
>
> 	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
>
> (thanks Miklos for formula). All other changes are moslty shuffling lines.
>
> The patch also contains one-line fix suggested by Miklos: the loop iterating
> over pages from inode mapping should interpret 'offset' as offset in the very
> first page only.

That fix is already in -linus, so let's leave it out of this patch.

Thanks,
Miklos

> ---
>  fs/fuse/dev.c |   26 ++++++++++++++++----------
>  1 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 6e38af5..cf69df3 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1562,13 +1562,24 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
>  	unsigned int num;
>  	unsigned int offset;
>  	size_t total_len = 0;
> +	int num_pages;
>  
> -	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
> +	offset = outarg->offset & ~PAGE_CACHE_MASK;
> +	file_size = i_size_read(inode);
> +
> +	num = outarg->size;
> +	if (outarg->offset > file_size)
> +		num = 0;
> +	else if (outarg->offset + num > file_size)
> +		num = file_size - outarg->offset;
> +
> +	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +	num_pages = min(num_pages, FUSE_MAX_PAGES_PER_REQ);
> +
> +	req = fuse_get_req_multipage(fc, num_pages);
>  	if (IS_ERR(req))
>  		return PTR_ERR(req);
>  
> -	offset = outarg->offset & ~PAGE_CACHE_MASK;
> -
>  	req->in.h.opcode = FUSE_NOTIFY_REPLY;
>  	req->in.h.nodeid = outarg->nodeid;
>  	req->in.numargs = 2;
> @@ -1577,14 +1588,8 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
>  	req->end = fuse_retrieve_end;
>  
>  	index = outarg->offset >> PAGE_CACHE_SHIFT;
> -	file_size = i_size_read(inode);
> -	num = outarg->size;
> -	if (outarg->offset > file_size)
> -		num = 0;
> -	else if (outarg->offset + num > file_size)
> -		num = file_size - outarg->offset;
>  
> -	while (num && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
> +	while (num && req->num_pages < num_pages) {
>  		struct page *page;
>  		unsigned int this_num;
>  
> @@ -1596,6 +1601,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
>  		req->pages[req->num_pages] = page;
>  		req->num_pages++;
>  
> +		offset = 0;
>  		num -= this_num;
>  		total_len += this_num;
>  		index++;

[PATCH 4/6] fuse: rework fuse_readpages()

[Maxim Patlasov]

The patch uses 'nr_pages' argument of fuse_readpages() as the heuristics for
number of page pointers to allocate.

This can be improved further by taking in consideration fc->max_read and gaps
between page indices, but it's not clear wheteher it's worthy or not.
---
 fs/fuse/file.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c811f3d..9a6dcc6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -641,6 +641,7 @@ struct fuse_fill_data {
 	struct fuse_req *req;
 	struct file *file;
 	struct inode *inode;
+	unsigned nr_pages;
 };
 
 static int fuse_readpages_fill(void *_data, struct page *page)
@@ -656,8 +657,10 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 	    (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
 	     (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
 	     req->pages[req->num_pages - 1]->index + 1 != page->index)) {
+		int nr_alloc = min_t(unsigned, data->nr_pages,
+				     FUSE_MAX_PAGES_PER_REQ);
 		fuse_send_readpages(req, data->file);
-		data->req = req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
+		data->req = req = fuse_get_req_multipage(fc, nr_alloc);
 		if (IS_ERR(req)) {
 			unlock_page(page);
 			return PTR_ERR(req);
@@ -666,6 +669,7 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 	page_cache_get(page);
 	req->pages[req->num_pages] = page;
 	req->num_pages++;
+	data->nr_pages--;
 	return 0;
 }
 
@@ -676,6 +680,7 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_fill_data data;
 	int err;
+	int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
 
 	err = -EIO;
 	if (is_bad_inode(inode))
@@ -683,7 +688,8 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 
 	data.file = file;
 	data.inode = inode;
-	data.req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
+	data.req = fuse_get_req_multipage(fc, nr_alloc);
+	data.nr_pages = nr_pages;
 	err = PTR_ERR(data.req);
 	if (IS_ERR(data.req))
 		goto out;

Re: [PATCH 4/6] fuse: rework fuse_readpages()

[Miklos Szeredi]

Maxim Patlasov <mpatlasov@parallels.com> writes:

> The patch uses 'nr_pages' argument of fuse_readpages() as the heuristics for
> number of page pointers to allocate.
>
> This can be improved further by taking in consideration fc->max_read and gaps
> between page indices, but it's not clear wheteher it's worthy or not.
> ---
>  fs/fuse/file.c |   10 ++++++++--
>  1 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index c811f3d..9a6dcc6 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -641,6 +641,7 @@ struct fuse_fill_data {
>  	struct fuse_req *req;
>  	struct file *file;
>  	struct inode *inode;
> +	unsigned nr_pages;
>  };
>  
>  static int fuse_readpages_fill(void *_data, struct page *page)
> @@ -656,8 +657,10 @@ static int fuse_readpages_fill(void *_data, struct page *page)
>  	    (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
>  	     (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
>  	     req->pages[req->num_pages - 1]->index + 1 != page->index)) {
> +		int nr_alloc = min_t(unsigned, data->nr_pages,
> +				     FUSE_MAX_PAGES_PER_REQ);
>  		fuse_send_readpages(req, data->file);
> -		data->req = req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
> +		data->req = req = fuse_get_req_multipage(fc, nr_alloc);
>  		if (IS_ERR(req)) {
>  			unlock_page(page);
>  			return PTR_ERR(req);
> @@ -666,6 +669,7 @@ static int fuse_readpages_fill(void *_data, struct page *page)
>  	page_cache_get(page);


Okay, this is where things get hairy and where we should do something like:

	if (WARN_ON(req->num_pages >= req->max_pages))
		return -EIO;

>  	req->pages[req->num_pages] = page;
>  	req->num_pages++;
> +	data->nr_pages--;
>  	return 0;
>  }
>  
> @@ -676,6 +680,7 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
>  	struct fuse_conn *fc = get_fuse_conn(inode);
>  	struct fuse_fill_data data;
>  	int err;
> +	int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
>  
>  	err = -EIO;
>  	if (is_bad_inode(inode))
> @@ -683,7 +688,8 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
>  
>  	data.file = file;
>  	data.inode = inode;
> -	data.req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
> +	data.req = fuse_get_req_multipage(fc, nr_alloc);
> +	data.nr_pages = nr_pages;
>  	err = PTR_ERR(data.req);
>  	if (IS_ERR(data.req))
>  		goto out;

[PATCH 5/6] fuse: rework fuse_perform_write()

[Maxim Patlasov]

The patch allocates as many page pointers in fuse_req as needed to cover
interval [pos .. pos+len-1]. FUSE_WR_PAGES macro is introduced to hide this
cumbersome arithmetics.
---
 fs/fuse/file.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9a6dcc6..84cc83c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -815,7 +815,8 @@ static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
 
 static ssize_t fuse_fill_write_pages(struct fuse_req *req,
 			       struct address_space *mapping,
-			       struct iov_iter *ii, loff_t pos)
+			       struct iov_iter *ii, loff_t pos,
+			       unsigned nr_pages)
 {
 	struct fuse_conn *fc = get_fuse_conn(mapping->host);
 	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
@@ -875,11 +876,16 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
 		if (!fc->big_writes)
 			break;
 	} while (iov_iter_count(ii) && count < fc->max_write &&
-		 req->num_pages < FUSE_MAX_PAGES_PER_REQ && offset == 0);
+		 req->num_pages < nr_pages && offset == 0);
 
 	return count > 0 ? count : err;
 }
 
+#define FUSE_WR_PAGES(pos, len) min_t(unsigned,				      \
+				      ((pos + len - 1) >> PAGE_CACHE_SHIFT) - \
+				      (pos >> PAGE_CACHE_SHIFT) + 1,	      \
+				      FUSE_MAX_PAGES_PER_REQ)
+
 static ssize_t fuse_perform_write(struct file *file,
 				  struct address_space *mapping,
 				  struct iov_iter *ii, loff_t pos)
@@ -895,14 +901,15 @@ static ssize_t fuse_perform_write(struct file *file,
 	do {
 		struct fuse_req *req;
 		ssize_t count;
+		unsigned nr_pages = FUSE_WR_PAGES(pos, iov_iter_count(ii));
 
-		req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
+		req = fuse_get_req_multipage(fc, nr_pages);
 		if (IS_ERR(req)) {
 			err = PTR_ERR(req);
 			break;
 		}
 
-		count = fuse_fill_write_pages(req, mapping, ii, pos);
+		count = fuse_fill_write_pages(req, mapping, ii, pos, nr_pages);
 		if (count <= 0) {
 			err = count;
 		} else {

Re: [PATCH 5/6] fuse: rework fuse_perform_write()

[Miklos Szeredi]

Maxim Patlasov <mpatlasov@parallels.com> writes:

> The patch allocates as many page pointers in fuse_req as needed to cover
> interval [pos .. pos+len-1]. FUSE_WR_PAGES macro is introduced to hide this
> cumbersome arithmetics.

Please don't ever use a macro for something which you can use an inline
function.

> ---
>  fs/fuse/file.c |   15 +++++++++++----
>  1 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 9a6dcc6..84cc83c 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -815,7 +815,8 @@ static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
>  
>  static ssize_t fuse_fill_write_pages(struct fuse_req *req,
>  			       struct address_space *mapping,
> -			       struct iov_iter *ii, loff_t pos)
> +			       struct iov_iter *ii, loff_t pos,
> +			       unsigned nr_pages)
>  {
>  	struct fuse_conn *fc = get_fuse_conn(mapping->host);
>  	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
> @@ -875,11 +876,16 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
>  		if (!fc->big_writes)
>  			break;
>  	} while (iov_iter_count(ii) && count < fc->max_write &&
> -		 req->num_pages < FUSE_MAX_PAGES_PER_REQ && offset == 0);
> +		 req->num_pages < nr_pages && offset == 0);
>  
>  	return count > 0 ? count : err;
>  }
>  
> +#define FUSE_WR_PAGES(pos, len) min_t(unsigned,				      \
> +				      ((pos + len - 1) >> PAGE_CACHE_SHIFT) - \
> +				      (pos >> PAGE_CACHE_SHIFT) + 1,	      \
> +				      FUSE_MAX_PAGES_PER_REQ)
> +
>  static ssize_t fuse_perform_write(struct file *file,
>  				  struct address_space *mapping,
>  				  struct iov_iter *ii, loff_t pos)
> @@ -895,14 +901,15 @@ static ssize_t fuse_perform_write(struct file *file,
>  	do {
>  		struct fuse_req *req;
>  		ssize_t count;
> +		unsigned nr_pages = FUSE_WR_PAGES(pos, iov_iter_count(ii));
>  
> -		req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
> +		req = fuse_get_req_multipage(fc, nr_pages);
>  		if (IS_ERR(req)) {
>  			err = PTR_ERR(req);
>  			break;
>  		}
>  
> -		count = fuse_fill_write_pages(req, mapping, ii, pos);
> +		count = fuse_fill_write_pages(req, mapping, ii, pos, nr_pages);
>  		if (count <= 0) {
>  			err = count;
>  		} else {

[PATCH 6/6] fuse: rework fuse_do_ioctl()

[Maxim Patlasov]

fuse_do_ioctl() already calculates the number of pages it's going to use. It is
stored in 'num_pages' variable. So the patch simply uses it for allocating
fuse_req.
---
 fs/fuse/file.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 84cc83c..abb070b 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1885,7 +1885,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
 		num_pages++;
 	}
 
-	req = fuse_get_req_multipage(fc, FUSE_MAX_PAGES_PER_REQ);
+	req = fuse_get_req_multipage(fc, num_pages);
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		req = NULL;

Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically

[Maxim V. Patlasov]

Hi,

I noticed that 'Signed-off-by' is missed in my patches. Very sorry for 
inconvenience. I'll be more careful next time.

Thanks,
Maxim

09/07/2012 09:40 PM, Maxim Patlasov пишет:
> Hi,
>
> Currently, any fuse request always includes inline pages[] array of
> FUSE_MAX_PAGES_PER_REQ elements. This is the waste of memory because
> in many cases smaller size would suffice.
> ...

Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically

[Maxim V. Patlasov]

Hi Miklos,

So far as no objections appeared, I'll go ahead and replace fuse 
req->page with req->pagevec. It will point to an array of structs:

struct page_vec {
     struct page    *pv_page;
     unsigned int    pv_len;
     unsigned int    pv_offset;
};

instead of 'struct page *' as it used to be. It seems to be what you 
suggested in one of your comments. Are you OK about it?

Thanks,
Maxim

09/07/2012 09:40 PM, Maxim Patlasov пишет:
> Hi,
>
> Currently, any fuse request always includes inline pages[] array of
> FUSE_MAX_PAGES_PER_REQ elements. This is the waste of memory because
> in many cases smaller size would suffice.
>
> The patch-set tries to allocate only as many elements of pages[] array as
> actaully needed. This will be even more useful in the future because of:
>
> 1. Mitsuo's patches making maximum read/write request size tunable.
> 2. My patches optimizing scatter-gather direct IO. To make them simplier I'll
> need to substitute array of 'struct page *' with array of 'struct bio_vec'.
> It would make memory overhead worse if implemented w/o this patch-set.
>
> Thanks,
> Maxim
>

Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically

[Miklos Szeredi]

"Maxim V. Patlasov" <mpatlasov@parallels.com> writes:

> Hi Miklos,
>
> So far as no objections appeared, I'll go ahead and replace fuse req->page with
> req->pagevec. It will point to an array of structs:
>
> struct page_vec {
>     struct page    *pv_page;
>     unsigned int    pv_len;
>     unsigned int    pv_offset;
> };
>
> instead of 'struct page *' as it used to be. It seems to be what you suggested
> in one of your comments. Are you OK about it?

Yes, that's exactly what I was thinking.

Thanks,
Miklos

Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically

[Maxim V. Patlasov]

Hi Miklos,

09/12/2012 08:49 PM, Miklos Szeredi пишет:
> "Maxim V. Patlasov" <mpatlasov@parallels.com> writes:
>
>> Hi Miklos,
>>
>> So far as no objections appeared, I'll go ahead and replace fuse req->page with
>> req->pagevec. It will point to an array of structs:
>>
>> struct page_vec {
>>      struct page    *pv_page;
>>      unsigned int    pv_len;
>>      unsigned int    pv_offset;
>> };
>>
>> instead of 'struct page *' as it used to be. It seems to be what you suggested
>> in one of your comments. Are you OK about it?
> Yes, that's exactly what I was thinking.

I've encountered a problem while trying to follow this approach. 
fuse_get_user_pages() passes 'req->pages' to get_user_pages_fast(). 
get_user_pages_fast() and friends are not ready to get a pointer to 
array of page_vec-s from fuse. I can see five ways to solve the problem:

1. Re-work get_user_pages_fast() and friends adding ability to fill 
page_vec array. Too much work. Very ugly. I strongly dislike this way.

2. Allocate a temporary array of page pointers in fuse_get_user_pages() 
to use as argument to get_user_pages_fast(). Ugly and may have 
performance impact. I dislike this way too.

3. Call get_user_pages_fast() for each page (i.e. pass npages == 1 to 
it). Easy to implement but may have performance impact. I'd refrain from it.

4. Keep req->pages 'as is', but add req->page_descs pointing to an array 
of <offset, len> structures. Looks clumsy, straightforward, but quite 
doable.

5. Use a hack in fuse_get_user_pages(): temporarily cast req->pagevecs 
to 'struct page **pages', pass it get_user_pages_fast(), then transform 
the content of req->pagevecs[] to have page pointers stored in proper 
places (like 'for (i=...) pagevecs[i].pv_page = pages[i];').

What do you think?

Btw, thanks a lot for careful review of patch-set. I agree with your 
comments. Next version will have those findings fixed.

Thanks,
Maxim

Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically

[Miklos Szeredi]

"Maxim V. Patlasov" <mpatlasov@parallels.com> writes:

> Hi Miklos,
>
> 09/12/2012 08:49 PM, Miklos Szeredi пишет:
>> "Maxim V. Patlasov" <mpatlasov@parallels.com> writes:
>>
>>> Hi Miklos,
>>>
>>> So far as no objections appeared, I'll go ahead and replace fuse req->page with
>>> req->pagevec. It will point to an array of structs:
>>>
>>> struct page_vec {
>>>      struct page    *pv_page;
>>>      unsigned int    pv_len;
>>>      unsigned int    pv_offset;
>>> };
>>>
>>> instead of 'struct page *' as it used to be. It seems to be what you suggested
>>> in one of your comments. Are you OK about it?
>> Yes, that's exactly what I was thinking.
>
> I've encountered a problem while trying to follow this
> approach. fuse_get_user_pages() passes 'req->pages' to
> get_user_pages_fast(). get_user_pages_fast() and friends are not ready to get a
> pointer to array of page_vec-s from fuse. I can see five ways to solve the
> problem:
>
> 1. Re-work get_user_pages_fast() and friends adding ability to fill page_vec
> array. Too much work. Very ugly. I strongly dislike this way.
>
> 2. Allocate a temporary array of page pointers in fuse_get_user_pages() to use
> as argument to get_user_pages_fast(). Ugly and may have performance impact. I
> dislike this way too.
>
> 3. Call get_user_pages_fast() for each page (i.e. pass npages == 1 to it). Easy
> to implement but may have performance impact. I'd refrain from it.
>
> 4. Keep req->pages 'as is', but add req->page_descs pointing to an array of
> <offset, len> structures. Looks clumsy, straightforward, but quite
> doable.
>
> 5. Use a hack in fuse_get_user_pages(): temporarily cast req->pagevecs to
> struct page **pages', pass it get_user_pages_fast(), then transform the content
> of req->pagevecs[] to have page pointers stored in proper places (like 'for
> (i=...) pagevecs[i].pv_page = pages[i];').
>
> What do you think?

I'd go for number 4.


Thanks,
Miklos