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fuse: allow kernel to access "direct_io" files 

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@suse.cz>
This commit is contained in:
Miklos Szeredi 2009-04-02 14:25:34 +02:00
parent 833bb3046b
commit f4975c67dd
2 changed files with 31 additions and 12 deletions
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1
fs/fuse/dir.c
View File

@ -1032,6 +1032,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
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);

42
fs/fuse/file.c
View File

@ -386,7 +386,6 @@ void fuse_read_fill(struct fuse_req *req, struct file *file,
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 *file, struct page *page)
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 fuse_req *req, struct file *file,
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_req *req, struct file *file,
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 file *file, struct inode *inode,
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(struct fuse_req *req,
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(struct fuse_req *req, int write)
}
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(&current->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(&current->mm->mmap_sem);
if (npages < 0)
@ -957,6 +967,15 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
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 file *file, const char __user *buf,
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 page *page)
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;