Home » Mailing lists » Devel » [PATCH 0/6] fuse: allocate req->pages[] dynamically
| [PATCH 0/6] fuse: allocate req->pages[] dynamically [message #47757] |
Fri, 07 September 2012 17:40  |
Maxim Patlasov
Messages: 45
Registered: July 2012
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Member |
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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
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| [PATCH 1/6] fuse: general infrastructure for pages[] of variable size [message #47758 is a reply to message #47757] |
Fri, 07 September 2012 17:41  |
Maxim Patlasov
Messages: 45
Registered: July 2012
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Member |
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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;
}
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| [PATCH 2/6] fuse: categorize fuse_get_req() [message #47759 is a reply to message #47757] |
Fri, 07 September 2012 17:41 |
Maxim Patlasov
Messages: 45
Registered: July 2012
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Member |
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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
...
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| [PATCH 3/6] fuse: rework fuse_retrieve() [message #47760 is a reply to message #47757] |
Fri, 07 September 2012 17:41 |
Maxim Patlasov
Messages: 45
Registered: July 2012
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Member |
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|
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++;
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| [PATCH 4/6] fuse: rework fuse_readpages() [message #47761 is a reply to message #47757] |
Fri, 07 September 2012 17:41 |
Maxim Patlasov
Messages: 45
Registered: July 2012
|
Member |
|
|
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;
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| [PATCH 5/6] fuse: rework fuse_perform_write() [message #47762 is a reply to message #47757] |
Fri, 07 September 2012 17:41 |
Maxim Patlasov
Messages: 45
Registered: July 2012
|
Member |
|
|
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 {
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| [PATCH 6/6] fuse: rework fuse_do_ioctl() [message #47763 is a reply to message #47757] |
Fri, 07 September 2012 17:41 |
Maxim Patlasov
Messages: 45
Registered: July 2012
|
Member |
|
|
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;
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| Re: [PATCH 1/6] fuse: general infrastructure for pages[] of variable size [message #47811 is a reply to message #47758] |
Wed, 12 September 2012 16:09 |
Miklos Szeredi
Messages: 161
Registered: April 2007
|
Senior Member |
|
|
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;
> }
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| Re: [PATCH 3/6] fuse: rework fuse_retrieve() [message #47813 is a reply to message #47760] |
Wed, 12 September 2012 16:23 |
Miklos Szeredi
Messages: 161
Registered: April 2007
|
Senior Member |
|
|
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++;
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| Re: [PATCH 4/6] fuse: rework fuse_readpages() [message #47814 is a reply to message #47761] |
Wed, 12 September 2012 16:41 |
Miklos Szeredi
Messages: 161
Registered: April 2007
|
Senior Member |
|
|
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;
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| Re: [PATCH 5/6] fuse: rework fuse_perform_write() [message #47815 is a reply to message #47762] |
Wed, 12 September 2012 16:43 |
Miklos Szeredi
Messages: 161
Registered: April 2007
|
Senior Member |
|
|
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 {
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| Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically [message #47842 is a reply to message #47816] |
Fri, 14 September 2012 13:18 |
Maxim Patlasov
Messages: 45
Registered: July 2012
|
Member |
|
|
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
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| Re: [PATCH 0/6] fuse: allocate req->pages[] dynamically [message #47847 is a reply to message #47842] |
Fri, 14 September 2012 14:39 |
Miklos Szeredi
Messages: 161
Registered: April 2007
|
Senior Member |
|
|
"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
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