According to Jens Axboe:
> On Thu, Feb 26 2004, Andrew Morton wrote:
> > Miquel van Smoorenburg <miquels@cistron.nl> wrote:
> > > Well, I'm looking for guidance from Jens first, since I'm not sure if
> > > he wants the first solution (congestion testing passed down), the second
> > > (congestion setting passed up) or both.
> >
> > The first patch looks nice. Why do we need the "pass it up" feature?
>
> Miquel, the newer patches do tend to get too complicated. I suppose I'm
> fine with the first patch as well, modulo the dm part (I'd suggest
> merging it without and talking to Joe about doing it properly).
Okay here you go. I added bdi_rw_congested() for code in xfs and ext2
that calls both bdi_read_congested() and bdi_write_congested() in
a row, and it was "free" anyway.
bdi_congested-core.patch
--- linux-2.6.3.orig/include/linux/backing-dev.h 2004-02-04 04:43:38.000000000 +0100
+++ linux-2.6.3-congested_fn/include/linux/backing-dev.h 2004-02-26 16:17:49.000000000 +0100
@@ -20,10 +20,14 @@ enum bdi_state {
BDI_unused, /* Available bits start here */
};
+typedef int (congested_fn)(void *, int);
+
struct backing_dev_info {
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
int memory_backed; /* Cannot clean pages with writepage */
+ congested_fn *congested_fn; /* Function pointer if device is md/dm */
+ void *congested_data; /* Pointer to aux data for congested func */
};
extern struct backing_dev_info default_backing_dev_info;
@@ -32,14 +36,27 @@ int writeback_acquire(struct backing_dev
int writeback_in_progress(struct backing_dev_info *bdi);
void writeback_release(struct backing_dev_info *bdi);
+static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
+{
+ if (bdi->congested_fn)
+ return bdi->congested_fn(bdi->congested_data, bdi_bits);
+ return (bdi->state & bdi_bits);
+}
+
static inline int bdi_read_congested(struct backing_dev_info *bdi)
{
- return test_bit(BDI_read_congested, &bdi->state);
+ return bdi_congested(bdi, 1 << BDI_read_congested);
}
static inline int bdi_write_congested(struct backing_dev_info *bdi)
{
- return test_bit(BDI_write_congested, &bdi->state);
+ return bdi_congested(bdi, 1 << BDI_write_congested);
+}
+
+static inline int bdi_rw_congested(struct backing_dev_info *bdi)
+{
+ return bdi_congested(bdi, (1 << BDI_read_congested)|
+ (1 << BDI_write_congested));
}
#endif /* _LINUX_BACKING_DEV_H */
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