fs: seq_file - add event counter to simplify poll() support

Moving the event counter into the dynamically allocated 'struc seq_file'
allows poll() support without the need to allocate its own tracking
structure.

All current users are switched over to use the new counter.

Requested-by: Andrew Morton akpm@linux-foundation.org
Acked-by: NeilBrown <neilb@suse.de>
Tested-by: Lucas De Marchi lucas.demarchi@profusion.mobi
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

6 files changed, 20 insertions, 43 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 91e31e260b4a..dfc9425db70b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6394,16 +6394,11 @@ static void md_seq_stop(struct seq_file *seq, void *v)
                 mddev_put(mddev);
 }
 
-struct mdstat_info {
-        int event;
-};
-
 static int md_seq_show(struct seq_file *seq, void *v)
 {
         mddev_t *mddev = v;
         sector_t sectors;
         mdk_rdev_t *rdev;
-        struct mdstat_info *mi = seq->private;
         struct bitmap *bitmap;
 
         if (v == (void*)1) {
@@ -6415,7 +6410,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 
                 spin_unlock(&pers_lock);
                 seq_printf(seq, "\n");
-                mi->event = atomic_read(&md_event_count);
+                seq->poll_event = atomic_read(&md_event_count);
                 return 0;
         }
         if (v == (void*)2) {
@@ -6527,26 +6522,21 @@ static const struct seq_operations md_seq_ops = {
 
 static int md_seq_open(struct inode *inode, struct file *file)
 {
+        struct seq_file *seq;
         int error;
-        struct mdstat_info *mi = kmalloc(sizeof(*mi), GFP_KERNEL);
-        if (mi == NULL)
-                return -ENOMEM;
 
         error = seq_open(file, &md_seq_ops);
         if (error)
-                kfree(mi);
-        else {
-                struct seq_file *p = file->private_data;
-                p->private = mi;
-                mi->event = atomic_read(&md_event_count);
-        }
+                return error;
+
+        seq = file->private_data;
+        seq->poll_event = atomic_read(&md_event_count);
         return error;
 }
 
 static unsigned int mdstat_poll(struct file *filp, poll_table *wait)
 {
-        struct seq_file *m = filp->private_data;
-        struct mdstat_info *mi = m->private;
+        struct seq_file *seq = filp->private_data;
         int mask;
 
         poll_wait(filp, &md_event_waiters, wait);
@@ -6554,7 +6544,7 @@ static unsigned int mdstat_poll(struct file *filp, poll_table *wait)
         /* always allow read */
         mask = POLLIN | POLLRDNORM;
 
-        if (mi->event != atomic_read(&md_event_count))
+        if (seq->poll_event != atomic_read(&md_event_count))
                 mask |= POLLERR | POLLPRI;
         return mask;
 }
diff --git a/fs/namespace.c b/fs/namespace.c
index fe59bd145d21..cda50fe9250a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -934,8 +934,8 @@ int mnt_had_events(struct proc_mounts *p)
         int res = 0;
 
         br_read_lock(vfsmount_lock);
-        if (p->event != ns->event) {
-                p->event = ns->event;
+        if (p->m.poll_event != ns->event) {
+                p->m.poll_event = ns->event;
                 res = 1;
         }
         br_read_unlock(vfsmount_lock);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index be1ff932033b..3dc5e2a5cc38 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -673,7 +673,7 @@ static int mounts_open_common(struct inode *inode, struct file *file,
         p->m.private = p;
         p->ns = ns;
         p->root = root;
-        p->event = ns->event;
+        p->m.poll_event = ns->event;
 
         return 0;
 
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 0b89efc6f215..29304855652d 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -18,7 +18,6 @@ struct proc_mounts {
         struct seq_file m; /* must be the first element */
         struct mnt_namespace *ns;
         struct path root;
-        int event;
 };
 
 struct fs_struct;
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 03c0232b4169..be720cd2038d 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -23,6 +23,7 @@ struct seq_file {
         u64 version;
         struct mutex lock;
         const struct seq_operations *op;
+        int poll_event;
         void *private;
 };
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index ff8dc1a18cb4..1b8c33907242 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1681,19 +1681,14 @@ out:
 }
 
 #ifdef CONFIG_PROC_FS
-struct proc_swaps {
-        struct seq_file seq;
-        int event;
-};
-
 static unsigned swaps_poll(struct file *file, poll_table *wait)
 {
-        struct proc_swaps *s = file->private_data;
+        struct seq_file *seq = file->private_data;
 
         poll_wait(file, &proc_poll_wait, wait);
 
-        if (s->event != atomic_read(&proc_poll_event)) {
-                s->event = atomic_read(&proc_poll_event);
+        if (seq->poll_event != atomic_read(&proc_poll_event)) {
+                seq->poll_event = atomic_read(&proc_poll_event);
                 return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
         }
 
@@ -1783,24 +1778,16 @@ static const struct seq_operations swaps_op = {
 
 static int swaps_open(struct inode *inode, struct file *file)
 {
-        struct proc_swaps *s;
+        struct seq_file *seq;
         int ret;
 
-        s = kmalloc(sizeof(struct proc_swaps), GFP_KERNEL);
-        if (!s)
-                return -ENOMEM;
-
-        file->private_data = s;
-
         ret = seq_open(file, &swaps_op);
-        if (ret) {
-                kfree(s);
+        if (ret)
                 return ret;
-        }
 
-        s->seq.private = s;
-        s->event = atomic_read(&proc_poll_event);
-        return ret;
+        seq = file->private_data;
+        seq->poll_event = atomic_read(&proc_poll_event);
+        return 0;
 }
 
 static const struct file_operations proc_swaps_operations = {