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SubjectRe: [PATCH] (resend) reuse xxx_fifo_fops for xxx_pipe_fops
Date
On Tuesday 01 July 2008 09:32, Andrew Morton wrote:
> > I noticed that read/write/rdwr_pipe_fops are (1) const and
> > (2) exactly identical to xxx_fifo_fops, which are also const.
> >
> > Attached patch #defines xxx_pipe_fops as aliases to xxx_fifo_fops.
> > Size difference:
> >
> > # size linux-2.6.25-rc6*/*/pipe.o
> > text data bss dec hex filename
> > 6534 144 0 6678 1a16 linux-2.6.25-rc6/fs/pipe.o
> > 5862 144 0 6006 1776 linux-2.6.25-rc6-pt/fs/pipe.o
> >
> > Run-tested on 2.6.26-rc8. Please apply.
> >
> > Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
>
> <argh, an attachment. save-as, read, edit..>

Let's see how KMail will cope with inline cut-n-paste...

> > -static const struct file_operations rdwr_pipe_fops = {
> > - .llseek = no_llseek,
> > - .read = do_sync_read,
> > - .aio_read = pipe_read,
> > - .write = do_sync_write,
> > - .aio_write = pipe_write,
> > - .poll = pipe_poll,
> > - .unlocked_ioctl = pipe_ioctl,
> > - .open = pipe_rdwr_open,
> > - .release = pipe_rdwr_release,
> > - .fasync = pipe_rdwr_fasync,
> > -};
> > +#define read_pipe_fops read_fifo_fops
> > +#define write_pipe_fops write_fifo_fops
> > +#define rdwr_pipe_fops rdwr_fifo_fops
>
> Well OK. But there's a risk that someone will go and modify
> read_fifo_fops without realising that they're also modifying
> read_pipe_fops.

Yes, it is possible.

> So it'd be better to rename read_fifo_fops to (say) shared_read_fops
> then do
>
> #define read_pipe_fops shared_read_fops
> #define read_fifo_fops shared_read_fops

I think since XXX_pipe_fops are only used in this file,
just explaining this in the comment would be enough.

Please take a look at the version below.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
--
vda


--- linux-2.6.26-rc8/fs/pipe.c.org Tue Jul 1 11:52:28 2008
+++ linux-2.6.26-rc8/fs/pipe.c Tue Jul 1 11:58:23 2008
@@ -777,6 +777,8 @@
/*
* The file_operations structs are not static because they
* are also used in linux/fs/fifo.c to do operations on FIFOs.
+ *
+ * Pipes reuse fifos' file_operations structs.
*/
const struct file_operations read_fifo_fops = {
.llseek = no_llseek,
@@ -815,43 +817,6 @@
.fasync = pipe_rdwr_fasync,
};

-static const struct file_operations read_pipe_fops = {
- .llseek = no_llseek,
- .read = do_sync_read,
- .aio_read = pipe_read,
- .write = bad_pipe_w,
- .poll = pipe_poll,
- .unlocked_ioctl = pipe_ioctl,
- .open = pipe_read_open,
- .release = pipe_read_release,
- .fasync = pipe_read_fasync,
-};
-
-static const struct file_operations write_pipe_fops = {
- .llseek = no_llseek,
- .read = bad_pipe_r,
- .write = do_sync_write,
- .aio_write = pipe_write,
- .poll = pipe_poll,
- .unlocked_ioctl = pipe_ioctl,
- .open = pipe_write_open,
- .release = pipe_write_release,
- .fasync = pipe_write_fasync,
-};
-
-static const struct file_operations rdwr_pipe_fops = {
- .llseek = no_llseek,
- .read = do_sync_read,
- .aio_read = pipe_read,
- .write = do_sync_write,
- .aio_write = pipe_write,
- .poll = pipe_poll,
- .unlocked_ioctl = pipe_ioctl,
- .open = pipe_rdwr_open,
- .release = pipe_rdwr_release,
- .fasync = pipe_rdwr_fasync,
-};
-
struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
{
struct pipe_inode_info *pipe;
@@ -927,7 +892,7 @@
inode->i_pipe = pipe;

pipe->readers = pipe->writers = 1;
- inode->i_fop = &rdwr_pipe_fops;
+ inode->i_fop = &rdwr_fifo_fops;

/*
* Mark the inode dirty from the very beginning,
@@ -978,7 +943,7 @@
d_instantiate(dentry, inode);

err = -ENFILE;
- f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipe_fops);
+ f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_fifo_fops);
if (!f)
goto err_dentry;
f->f_mapping = inode->i_mapping;
@@ -1021,7 +986,7 @@

f->f_pos = 0;
f->f_flags = O_RDONLY;
- f->f_op = &read_pipe_fops;
+ f->f_op = &read_fifo_fops;
f->f_mode = FMODE_READ;
f->f_version = 0;


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