On systems with very large numbers (> 1600 or so) of SCSI devices,
cat /proc/scsi/scsi ends up failing with -ENOMEM. This is due to
the show routine simply iterating over all of the devices with
bus_for_each_dev(), and trying to dump all of them into the buffer
at the same time. On my test system (using scsi_debug with 4064 devices),
the output ends up being ~ 632k, far more than kmalloc will typically allow.
This patch uses seq_file directly instead of single_file, and breaks up
the operations into the 4 seq_file callbacks. The result is that
each show() operation only dumps ~ 180 bytes into the buffer at a time
so we don't run out of memory.
Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
---
drivers/scsi/scsi_proc.c | 69 ++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 63 insertions(+), 6 deletions(-)
diff -rup a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c
--- a/drivers/scsi/scsi_proc.c 2007-04-12 13:41:06.000000000 -0400
+++ b/drivers/scsi/scsi_proc.c 2007-04-12 13:47:38.000000000 -0400
@@ -294,20 +294,77 @@ static ssize_t proc_scsi_write(struct fi
return err;
}
-static int proc_scsi_show(struct seq_file *s, void *p)
+static struct device *next_device(struct klist_iter *i)
{
- seq_printf(s, "Attached devices:\n");
- bus_for_each_dev(&scsi_bus_type, NULL, s, proc_print_scsidevice);
- return 0;
+ struct klist_node *n = klist_next(i);
+ return n ? container_of(n, struct device, knode_bus) : NULL;
+}
+
+static void *scsi_seq_start(struct seq_file *sfile, loff_t *pos)
+{
+ struct klist_iter *iter;
+ struct device *dev = NULL;
+ loff_t l = *pos;
+
+ iter = kmalloc(sizeof (*iter), GFP_KERNEL);
+ if (!iter)
+ return ERR_PTR(-ENOMEM);
+
+ klist_iter_init_node(&scsi_bus_type.klist_devices, iter, NULL);
+
+ do {
+ dev = next_device(iter);
+ } while (l-- && dev);
+
+ sfile->private = iter;
+ return dev;
}
+static void *scsi_seq_next(struct seq_file *sfile, void *v, loff_t *pos)
+{
+ struct klist_iter *iter = (struct klist_iter *)sfile->private;
+ ++*pos;
+ return next_device(iter);
+}
+
+static void scsi_seq_stop(struct seq_file *sfile, void *v)
+{
+ struct klist_iter *iter = (struct klist_iter *)sfile->private;
+ sfile->private = NULL;
+ klist_iter_exit(iter);
+ kfree(iter);
+}
+
+static int scsi_seq_show(struct seq_file *sfile, void *v)
+{
+ struct klist_iter *iter = (struct klist_iter *)sfile->private;
+ struct device *dev = (struct device *)v;
+ struct klist_node *head;
+
+ spin_lock(&iter->i_klist->k_lock);
+ head = container_of(iter->i_klist->k_list.next,
+ struct klist_node, n_node);
+ if (&dev->knode_bus == head)
+ seq_puts(sfile, "Attached devices:\n");
+ spin_unlock(&iter->i_klist->k_lock);
+
+ return proc_print_scsidevice(dev, sfile);
+}
+
+static struct seq_operations scsi_seq_ops = {
+ .start = scsi_seq_start,
+ .next = scsi_seq_next,
+ .stop = scsi_seq_stop,
+ .show = scsi_seq_show
+};
+
static int proc_scsi_open(struct inode *inode, struct file *file)
{
/*
* We don't really needs this for the write case but it doesn't
* harm either.
*/
- return single_open(file, proc_scsi_show, NULL);
+ return seq_open(file, &scsi_seq_ops);
}
static struct file_operations proc_scsi_operations = {
@@ -315,7 +372,7 @@ static struct file_operations proc_scsi_
.read = seq_read,
.write = proc_scsi_write,
.llseek = seq_lseek,
- .release = single_release,
+ .release = seq_release,
};
int __init scsi_init_procfs(void)
-
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