Attached is a cleanup of fs/pipe.c, against 2.5.14-dj2.
Main changes:
* 50 lines shorter
* fifo open now runs without the big kernel lock. The code didn't rely
on the blk since ~2.3.52.
* only update mtime, atime, ctime if a nonzero amount of data was
transfered.
* enable syscall merging for O_NONBLOCK pipe_read.
* fix a race that could trigger a wakeup storm if multiple threads read
from the same pipe.
The patch doesn't apply to 2.5.15 due to the fasync support.
--
Manfred
--------------819B7409D2AE061D85A23C58
Content-Type: text/plain; charset=us-ascii;
name="patch-simplepipe"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="patch-simplepipe"
// $Header$
// Kernel Version:
// VERSION = 2
// PATCHLEVEL = 5
// SUBLEVEL = 14
// EXTRAVERSION =-dj2
--- 2.5/fs/pipe.c Thu May 9 12:52:13 2002
+++ build-2.5/fs/pipe.c Thu May 9 23:07:58 2002
@@ -25,6 +25,9 @@
*
* FIFOs and Pipes now generate SIGIO for both readers and writers.
* -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
+ *
+ * pipe_read & write cleanup
+ * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
*/
/* Drop the inode semaphore and wait for a pipe event, atomically */
@@ -44,99 +47,81 @@
pipe_read(struct file *filp, char *buf, size_t count, loff_t *ppos)
{
struct inode *inode = filp->f_dentry->d_inode;
- ssize_t size, read, ret;
+ int do_wakeup;
+ ssize_t ret;
- /* Seeks are not allowed on pipes. */
- ret = -ESPIPE;
- read = 0;
- if (ppos != &filp->f_pos)
- goto out_nolock;
+ /* pread is not allowed on pipes. */
+ if (unlikely(ppos != &filp->f_pos))
+ return -ESPIPE;
+
+ /* Null read succeeds. */
+ if (unlikely(count == 0))
+ return 0;
- /* Always return 0 on null read. */
+ do_wakeup = 0;
ret = 0;
- if (count == 0)
- goto out_nolock;
+ down(PIPE_SEM(*inode));
+ for (;;) {
+ int size = PIPE_LEN(*inode);
+ if (size) {
+ char *pipebuf = PIPE_BASE(*inode) + PIPE_START(*inode);
+ ssize_t chars = PIPE_MAX_RCHUNK(*inode);
- /* Get the pipe semaphore */
- ret = -ERESTARTSYS;
- if (down_interruptible(PIPE_SEM(*inode)))
- goto out_nolock;
-
- if (PIPE_EMPTY(*inode)) {
-do_more_read:
- ret = 0;
- if (!PIPE_WRITERS(*inode))
- goto out;
+ if (chars > count)
+ chars = count;
+ if (chars > size)
+ chars = size;
- ret = -EAGAIN;
- if (filp->f_flags & O_NONBLOCK)
- goto out;
-
- for (;;) {
- PIPE_WAITING_READERS(*inode)++;
- pipe_wait(inode);
- PIPE_WAITING_READERS(*inode)--;
- ret = -ERESTARTSYS;
- if (signal_pending(current))
- goto out;
- ret = 0;
- if (!PIPE_EMPTY(*inode))
+ if (copy_to_user(buf, pipebuf, chars)) {
+ if (!ret) ret = -EFAULT;
break;
- if (!PIPE_WRITERS(*inode))
- goto out;
- }
- }
+ }
+ ret += chars;
- /* Read what data is available. */
- ret = -EFAULT;
- while (count > 0 && (size = PIPE_LEN(*inode))) {
- char *pipebuf = PIPE_BASE(*inode) + PIPE_START(*inode);
- ssize_t chars = PIPE_MAX_RCHUNK(*inode);
-
- if (chars > count)
- chars = count;
- if (chars > size)
- chars = size;
-
- if (copy_to_user(buf, pipebuf, chars))
- goto out;
-
- read += chars;
- PIPE_START(*inode) += chars;
- PIPE_START(*inode) &= (PIPE_SIZE - 1);
- PIPE_LEN(*inode) -= chars;
- count -= chars;
- buf += chars;
+ PIPE_START(*inode) += chars;
+ PIPE_START(*inode) &= (PIPE_SIZE - 1);
+ PIPE_LEN(*inode) -= chars;
+ count -= chars;
+ buf += chars;
+ do_wakeup = 1;
+ }
+ if (!count)
+ break; /* common path: read succeeded */
+ if (PIPE_LEN(*inode)) /* test for cyclic buffers */
+ continue;
+ if (!PIPE_WRITERS(*inode))
+ break;
+ if (!PIPE_WAITING_WRITERS(*inode)) {
+ /* syscall merging: Usually we must not sleep
+ * if O_NONBLOCK is set, or if we got some data.
+ * But if a writer sleeps in kernel space, then
+ * we can wait for that data without violating POSIX.
+ */
+ if (ret)
+ break;
+ if (filp->f_flags & O_NONBLOCK) {
+ ret = -EAGAIN;
+ break;
+ }
+ }
+ if (signal_pending(current)) {
+ if (!ret) ret = -ERESTARTSYS;
+ break;
+ }
+ if (do_wakeup) {
+ wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
+ }
+ pipe_wait(inode);
}
-
- /* Cache behaviour optimization */
- if (!PIPE_LEN(*inode))
- PIPE_START(*inode) = 0;
-
- if (count && PIPE_WAITING_WRITERS(*inode) && !(filp->f_flags & O_NONBLOCK)) {
- /*
- * We know that we are going to sleep: signal
- * writers synchronously that there is more
- * room.
- */
+ up(PIPE_SEM(*inode));
+ /* Signal writers asynchronously that there is more room. */
+ if (do_wakeup) {
wake_up_interruptible(PIPE_WAIT(*inode));
- kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
- if (!PIPE_EMPTY(*inode))
- BUG();
- goto do_more_read;
+ kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
}
- /* Signal writers asynchronously that there is more room. */
- wake_up_interruptible(PIPE_WAIT(*inode));
- kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
-
- ret = read;
-out:
- up(PIPE_SEM(*inode));
-out_nolock:
- if (read)
- ret = read;
-
- UPDATE_ATIME(inode);
+ if (ret > 0)
+ UPDATE_ATIME(inode);
return ret;
}
@@ -144,116 +129,90 @@
pipe_write(struct file *filp, const char *buf, size_t count, loff_t *ppos)
{
struct inode *inode = filp->f_dentry->d_inode;
- ssize_t free, written, ret;
-
- /* Seeks are not allowed on pipes. */
- ret = -ESPIPE;
- written = 0;
- if (ppos != &filp->f_pos)
- goto out_nolock;
+ ssize_t ret;
+ size_t min;
+ int do_wakeup;
+
+ /* pwrite is not allowed on pipes. */
+ if (unlikely(ppos != &filp->f_pos))
+ return -ESPIPE;
+
+ /* Null write succeeds. */
+ if (unlikely(count == 0))
+ return 0;
- /* Null write succeeds. */
+ do_wakeup = 0;
ret = 0;
- if (count == 0)
- goto out_nolock;
-
- ret = -ERESTARTSYS;
- if (down_interruptible(PIPE_SEM(*inode)))
- goto out_nolock;
-
- /* No readers yields SIGPIPE. */
- if (!PIPE_READERS(*inode))
- goto sigpipe;
-
- /* If count <= PIPE_BUF, we have to make it atomic. */
- free = (count <= PIPE_BUF ? count : 1);
-
- /* Wait, or check for, available space. */
- if (filp->f_flags & O_NONBLOCK) {
- ret = -EAGAIN;
- if (PIPE_FREE(*inode) < free)
- goto out;
- } else {
- while (PIPE_FREE(*inode) < free) {
- PIPE_WAITING_WRITERS(*inode)++;
- pipe_wait(inode);
- PIPE_WAITING_WRITERS(*inode)--;
- ret = -ERESTARTSYS;
- if (signal_pending(current))
- goto out;
-
- if (!PIPE_READERS(*inode))
- goto sigpipe;
+ min = count;
+ if (min > PIPE_BUF)
+ min = 1;
+ down(PIPE_SEM(*inode));
+ for (;;) {
+ int free;
+ if (!PIPE_READERS(*inode)) {
+ send_sig(SIGPIPE, current, 0);
+ if (!ret) ret = -EPIPE;
+ break;
}
- }
-
- /* Copy into available space. */
- ret = -EFAULT;
- while (count > 0) {
- int space;
- char *pipebuf = PIPE_BASE(*inode) + PIPE_END(*inode);
- ssize_t chars = PIPE_MAX_WCHUNK(*inode);
-
- if ((space = PIPE_FREE(*inode)) != 0) {
+ free = PIPE_FREE(*inode);
+ if (free >= min) {
+ /* transfer data */
+ ssize_t chars = PIPE_MAX_WCHUNK(*inode);
+ char *pipebuf = PIPE_BASE(*inode) + PIPE_END(*inode);
+ /* Always wakeup, even if the copy fails. Otherwise
+ * we lock up (O_NONBLOCK-)readers that sleep due to
+ * syscall merging.
+ */
+ do_wakeup = 1;
if (chars > count)
chars = count;
- if (chars > space)
- chars = space;
+ if (chars > free)
+ chars = free;
- if (copy_from_user(pipebuf, buf, chars))
- goto out;
+ if (copy_from_user(pipebuf, buf, chars)) {
+ if (!ret) ret = -EFAULT;
+ break;
+ }
- written += chars;
+ ret += chars;
PIPE_LEN(*inode) += chars;
count -= chars;
buf += chars;
- space = PIPE_FREE(*inode);
+ }
+ if (!count)
+ break;
+ if (PIPE_FREE(*inode) && ret) {
+ /* handle cyclic data buffers */
+ min = 1;
continue;
}
-
- ret = written;
- if (filp->f_flags & O_NONBLOCK)
+ if (filp->f_flags & O_NONBLOCK) {
+ if (!ret) ret = -EAGAIN;
break;
-
- do {
- /*
- * Synchronous wake-up: it knows that this process
- * is going to give up this CPU, so it doesnt have
- * to do idle reschedules.
- */
+ }
+ if (signal_pending(current)) {
+ if (!ret) ret = -ERESTARTSYS;
+ break;
+ }
+ if (do_wakeup) {
wake_up_interruptible(PIPE_WAIT(*inode));
- kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
- PIPE_WAITING_WRITERS(*inode)++;
- pipe_wait(inode);
- PIPE_WAITING_WRITERS(*inode)--;
- if (signal_pending(current))
- goto out;
- if (!PIPE_READERS(*inode))
- goto sigpipe;
- } while (!PIPE_FREE(*inode));
- ret = -EFAULT;
+ kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
+ do_wakeup = 0;
+ }
+ PIPE_WAITING_WRITERS(*inode)++;
+ pipe_wait(inode);
+ PIPE_WAITING_WRITERS(*inode)--;
}
-
- /* Signal readers asynchronously that there is more data. */
- wake_up_interruptible(PIPE_WAIT(*inode));
- kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
-
- inode->i_ctime = inode->i_mtime = CURRENT_TIME;
- mark_inode_dirty(inode);
-
-out:
up(PIPE_SEM(*inode));
-out_nolock:
- if (written)
- ret = written;
+ if (do_wakeup) {
+ wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
+ }
+ if (ret > 0) {
+ inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+ mark_inode_dirty(inode);
+ }
return ret;
-
-sigpipe:
- if (written)
- goto out;
- up(PIPE_SEM(*inode));
- send_sig(SIGPIPE, current, 0);
- return -EPIPE;
}
static ssize_t
@@ -527,7 +486,7 @@
PIPE_BASE(*inode) = (char*) page;
PIPE_START(*inode) = PIPE_LEN(*inode) = 0;
PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0;
- PIPE_WAITING_READERS(*inode) = PIPE_WAITING_WRITERS(*inode) = 0;
+ PIPE_WAITING_WRITERS(*inode) = 0;
PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1;
*PIPE_FASYNC_READERS(*inode) = *PIPE_FASYNC_WRITERS(*inode) = NULL;
--- 2.5/include/linux/pipe_fs_i.h Thu May 9 12:52:13 2002
+++ build-2.5/include/linux/pipe_fs_i.h Thu May 9 22:22:28 2002
@@ -9,7 +9,6 @@
unsigned int start;
unsigned int readers;
unsigned int writers;
- unsigned int waiting_readers;
unsigned int waiting_writers;
unsigned int r_counter;
unsigned int w_counter;
@@ -28,7 +27,6 @@
#define PIPE_LEN(inode) ((inode).i_pipe->len)
#define PIPE_READERS(inode) ((inode).i_pipe->readers)
#define PIPE_WRITERS(inode) ((inode).i_pipe->writers)
-#define PIPE_WAITING_READERS(inode) ((inode).i_pipe->waiting_readers)
#define PIPE_WAITING_WRITERS(inode) ((inode).i_pipe->waiting_writers)
#define PIPE_RCOUNTER(inode) ((inode).i_pipe->r_counter)
#define PIPE_WCOUNTER(inode) ((inode).i_pipe->w_counter)
--- 2.5/fs/fifo.c Fri Mar 1 23:01:45 2002
+++ build-2.5/fs/fifo.c Thu May 9 21:37:58 2002
@@ -12,7 +12,6 @@
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
-#include <linux/fs.h>
static void wait_for_partner(struct inode* inode, unsigned int* cnt)
{
@@ -33,10 +32,8 @@
{
int ret;
- ret = -ERESTARTSYS;
- lock_kernel();
if (down_interruptible(PIPE_SEM(*inode)))
- goto err_nolock_nocleanup;
+ return -ERESTARTSYS;
if (!inode->i_pipe) {
ret = -ENOMEM;
@@ -117,7 +114,6 @@
/* Ok! */
up(PIPE_SEM(*inode));
- unlock_kernel();
return 0;
err_rd:
@@ -142,9 +138,6 @@
err_nocleanup:
up(PIPE_SEM(*inode));
-
-err_nolock_nocleanup:
- unlock_kernel();
return ret;
}
--------------819B7409D2AE061D85A23C58--
-
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