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Date: Mon, 30 Mar 2009 22:02:17 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: [patch 1/3] fuse: allow kernel to access "direct_io" files
From: Miklos Szeredi <mszeredi@...e.cz>
Allow the kernel read and write on "direct_io" files. This is
necessary for nfs export and execute support.
The implementation is simple: if an access from the kernel is
detected, don't perform get_user_pages(), just use the kernel address
provided by the requester to copy from/to the userspace filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
fs/fuse/dir.c | 1 +
fs/fuse/file.c | 53 ++++++++++++++++++++++++++++++++++++++++-------------
2 files changed, 41 insertions(+), 13 deletions(-)
Index: linux-2.6/fs/fuse/file.c
===================================================================
--- linux-2.6.orig/fs/fuse/file.c 2009-03-25 10:30:52.000000000 +0100
+++ linux-2.6/fs/fuse/file.c 2009-03-25 10:35:22.000000000 +0100
@@ -386,7 +386,6 @@ void fuse_read_fill(struct fuse_req *req
req->in.numargs = 1;
req->in.args[0].size = sizeof(struct fuse_read_in);
req->in.args[0].value = inarg;
- req->out.argpages = 1;
req->out.argvar = 1;
req->out.numargs = 1;
req->out.args[0].size = count;
@@ -453,6 +452,7 @@ static int fuse_readpage(struct file *fi
attr_ver = fuse_get_attr_version(fc);
req->out.page_zeroing = 1;
+ req->out.argpages = 1;
req->num_pages = 1;
req->pages[0] = page;
num_read = fuse_send_read(req, file, inode, pos, count, NULL);
@@ -510,6 +510,8 @@ static void fuse_send_readpages(struct f
struct fuse_conn *fc = get_fuse_conn(inode);
loff_t pos = page_offset(req->pages[0]);
size_t count = req->num_pages << PAGE_CACHE_SHIFT;
+
+ req->out.argpages = 1;
req->out.page_zeroing = 1;
fuse_read_fill(req, file, inode, pos, count, FUSE_READ);
req->misc.read.attr_ver = fuse_get_attr_version(fc);
@@ -621,7 +623,6 @@ static void fuse_write_fill(struct fuse_
inarg->flags = file ? file->f_flags : 0;
req->in.h.opcode = FUSE_WRITE;
req->in.h.nodeid = get_node_id(inode);
- req->in.argpages = 1;
req->in.numargs = 2;
if (fc->minor < 9)
req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
@@ -695,6 +696,7 @@ static int fuse_buffered_write(struct fi
if (IS_ERR(req))
return PTR_ERR(req);
+ req->in.argpages = 1;
req->num_pages = 1;
req->pages[0] = page;
req->page_offset = offset;
@@ -771,6 +773,7 @@ static ssize_t fuse_fill_write_pages(str
size_t count = 0;
int err;
+ req->in.argpages = 1;
req->page_offset = offset;
do {
@@ -935,21 +938,28 @@ static void fuse_release_user_pages(stru
}
static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
- unsigned nbytes, int write)
+ unsigned *nbytesp, int write)
{
+ unsigned nbytes = *nbytesp;
unsigned long user_addr = (unsigned long) buf;
unsigned offset = user_addr & ~PAGE_MASK;
int npages;
- /* This doesn't work with nfsd */
- if (!current->mm)
- return -EPERM;
+ /* Special case for kernel I/O: can copy directly into the buffer */
+ if (segment_eq(get_fs(), KERNEL_DS)) {
+ if (write)
+ req->in.args[1].value = (void *) user_addr;
+ else
+ req->out.args[0].value = (void *) user_addr;
+
+ return 0;
+ }
nbytes = min(nbytes, (unsigned) FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
down_read(¤t->mm->mmap_sem);
- npages = get_user_pages(current, current->mm, user_addr, npages, write,
+ npages = get_user_pages(current, current->mm, user_addr, npages, !write,
0, req->pages, NULL);
up_read(¤t->mm->mmap_sem);
if (npages < 0)
@@ -957,6 +967,15 @@ static int fuse_get_user_pages(struct fu
req->num_pages = npages;
req->page_offset = offset;
+
+ if (write)
+ req->in.argpages = 1;
+ else
+ req->out.argpages = 1;
+
+ nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
+ *nbytesp = min(*nbytesp, nbytes);
+
return 0;
}
@@ -979,15 +998,13 @@ static ssize_t fuse_direct_io(struct fil
while (count) {
size_t nres;
- size_t nbytes_limit = min(count, nmax);
- size_t nbytes;
- int err = fuse_get_user_pages(req, buf, nbytes_limit, !write);
+ size_t nbytes = min(count, nmax);
+ int err = fuse_get_user_pages(req, buf, &nbytes, write);
if (err) {
res = err;
break;
}
- nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
- nbytes = min(nbytes_limit, nbytes);
+
if (write)
nres = fuse_send_write(req, file, inode, pos, nbytes,
current->files);
@@ -1163,6 +1180,7 @@ static int fuse_writepage_locked(struct
fuse_write_fill(req, NULL, ff, inode, page_offset(page), 0, 1);
copy_highpage(tmp_page, page);
+ req->in.argpages = 1;
req->num_pages = 1;
req->pages[0] = tmp_page;
req->page_offset = 0;
Index: linux-2.6/fs/fuse/dir.c
===================================================================
--- linux-2.6.orig/fs/fuse/dir.c 2009-03-25 10:31:06.000000000 +0100
+++ linux-2.6/fs/fuse/dir.c 2009-03-25 10:31:10.000000000 +0100
@@ -1032,6 +1032,7 @@ static int fuse_readdir(struct file *fil
fuse_put_request(fc, req);
return -ENOMEM;
}
+ req->out.argpages = 1;
req->num_pages = 1;
req->pages[0] = page;
fuse_read_fill(req, file, inode, file->f_pos, PAGE_SIZE, FUSE_READDIR);
--
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