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Subjectsendfile bugs(?)


There seems to be couple of issues in sendfile code.
- read_write.c: sys_sendfile:do_sendfile checks for ppos
to be NULL, the intension is checking the contents for
zero.
- locks_verify_write() may checks at different offset for
permission, and copy at different offset, since it is also
using out_file->f_pos. And also it will be cleaner to
update out_file->f_pos atomically only when it succeeds.
It also deletes the dependency on f_pos from filemap.c.

Thanks,
Prasanna.

--- fs/read_write.c.saved Tue Aug 10 19:10:35 2004
+++ fs/read_write.c Tue Aug 10 19:34:09 2004
@@ -546,6 +546,7 @@
loff_t pos;
ssize_t retval;
int fput_needed_in, fput_needed_out;
+ struct sendfile_target target;

/*
* Get input file, and verify that it is ok..
@@ -562,7 +563,7 @@
goto fput_in;
if (!in_file->f_op || !in_file->f_op->sendfile)
goto fput_in;
- if (!ppos)
+ if (!*ppos)
ppos = &in_file->f_pos;
retval = locks_verify_area(FLOCK_VERIFY_READ, in_inode, in_file,
*ppos, count);
if (retval)
@@ -585,7 +586,10 @@
if (!out_file->f_op || !out_file->f_op->sendpage)
goto fput_out;
out_inode = out_file->f_dentry->d_inode;
- retval = locks_verify_area(FLOCK_VERIFY_WRITE, out_inode,
out_file, out_file->f_pos, count);
+
+ target.file = out_file;
+ target.pos = out_file->f_pos;
+ retval = locks_verify_area(FLOCK_VERIFY_WRITE, out_inode,
out_file, target.pos, count);
if (retval)
goto fput_out;

@@ -607,10 +611,12 @@
count = max - pos;
}

- retval = in_file->f_op->sendfile(in_file, ppos, count,
file_send_actor, out_file);
+ retval = in_file->f_op->sendfile(in_file, ppos, count,
file_send_actor, &target);

if (*ppos > max)
retval = -EOVERFLOW;
+ if (!retval)
+ out_file->f_pos = target.pos;

fput_out:
fput_light(out_file, fput_needed_out);
--- include/linux/fs.h.saved Tue Aug 10 19:17:05 2004
+++ include/linux/fs.h Tue Aug 10 19:24:53 2004
@@ -851,9 +851,15 @@
size_t count;
char __user * buf;
int error;
+ loff_t *pos;
} read_descriptor_t;

typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
unsigned long, unsigned long);
+
+struct sendfile_target {
+ struct file *file;
+ loff_t pos;
+};

/*
* NOTE:
--- mm/filemap.c.saved Tue Aug 10 19:13:07 2004
+++ mm/filemap.c Tue Aug 10 19:24:35 2004
@@ -941,13 +941,14 @@
{
ssize_t written;
unsigned long count = desc->count;
- struct file *file = (struct file *) desc->buf;
+ struct file *file = desc->buf;
+ loff_t *ppos = desc->pos;

if (size > count)
size = count;

written = file->f_op->sendpage(file, page, offset,
- size, &file->f_pos, size<count);
+ size, ppos, size<count);
if (written < 0) {
desc->error = written;
written = 0;
@@ -958,17 +959,19 @@
}

ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
- size_t count, read_actor_t actor, void __user
*target)
+ size_t count, read_actor_t actor, void __user
*arg)
{
read_descriptor_t desc;
+ struct sendfile_target *target = arg;

if (!count)
return 0;

desc.written = 0;
desc.count = count;
- desc.buf = target;
+ desc.buf = target->file;
desc.error = 0;
+ desc.pos = &target->pos;

do_generic_file_read(in_file, ppos, &desc, actor);
if (desc.written)
-
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