Hi Wei Yang, On 03/25/18 at 12:13am, Wei Yang wrote: > On Sat, Mar 24, 2018 at 09:33:30PM +0800, Baoquan He wrote: > >> > >> Yes. That sounds perfectly acceptable. > >> > >> It would be interesting to see what this approach looks like, if you > >> have time to toss something together? > > > >OK, will make patches for reviewing. Thanks! > > Hi, Baoquan, Andrew > > I have come up with an implementation for top-down search the ram resources. > Hope this would meet your need. Thanks for telling and your effort. Glad to know I am not the only buyer of walk_system_ram_res_rev. I am fine with other ways to make it, people can compare them and know which one is better. I am working to use the list_head instead, the doubly linked list way as Andrew suggested. Andrew and other people can help make a choice. It won't be long. Thanks Baoquan > > From b36d50487f1d4e4d6a5103965a27101b3121e0ea Mon Sep 17 00:00:00 2001 > From: Wei Yang <richard.weiyang@xxxxxxxxx> > Date: Sat, 24 Mar 2018 23:25:46 +0800 > Subject: [PATCH] kernel/resource: add walk_system_ram_res_rev() > > As discussed on https://patchwork.kernel.org/patch/10300819/, this patch > comes up with a variant implementation of walk_system_ram_res_rev(), which > uses iteration instead of allocating array to store those resources. > > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> > --- > include/linux/ioport.h | 3 ++ > kernel/resource.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 116 insertions(+) > > diff --git a/include/linux/ioport.h b/include/linux/ioport.h > index da0ebaec25f0..473f1d9cb97e 100644 > --- a/include/linux/ioport.h > +++ b/include/linux/ioport.h > @@ -277,6 +277,9 @@ extern int > walk_system_ram_res(u64 start, u64 end, void *arg, > int (*func)(struct resource *, void *)); > extern int > +walk_system_ram_res_rev(u64 start, u64 end, void *arg, > + int (*func)(struct resource *, void *)); > +extern int > walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end, > void *arg, int (*func)(struct resource *, void *)); > > diff --git a/kernel/resource.c b/kernel/resource.c > index 769109f20fb7..ddf6b4c41498 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > @@ -73,6 +73,38 @@ static struct resource *next_resource(struct resource *p, bool sibling_only) > return p->sibling; > } > > +static struct resource *prev_resource(struct resource *p, bool sibling_only) > +{ > + struct resource *prev; > + if (NULL == iomem_resource.child) > + return NULL; > + > + if (p == NULL) { > + prev = iomem_resource.child; > + while (prev->sibling) > + prev = prev->sibling; > + } else { > + if (p->parent->child == p) { > + return p->parent; > + } > + > + for (prev = p->parent->child; prev->sibling != p; > + prev = prev->sibling) {} > + } > + > + /* Caller wants to traverse through siblings only */ > + if (sibling_only) > + return prev; > + > + for (;prev->child;) { > + prev = prev->child; > + > + while (prev->sibling) > + prev = prev->sibling; > + } > + return prev; > +} > + > static void *r_next(struct seq_file *m, void *v, loff_t *pos) > { > struct resource *p = v; > @@ -401,6 +433,47 @@ static int find_next_iomem_res(struct resource *res, unsigned long desc, > return 0; > } > > +/* > + * Finds the highest iomem resource existing within [res->start.res->end). > + * The caller must specify res->start, res->end, res->flags, and optionally > + * desc. If found, returns 0, res is overwritten, if not found, returns -1. > + * This function walks the whole tree and not just first level children until > + * and unless first_level_children_only is true. > + */ > +static int find_prev_iomem_res(struct resource *res, unsigned long desc, > + bool first_level_children_only) > +{ > + struct resource *p; > + > + BUG_ON(!res); > + BUG_ON(res->start >= res->end); > + > + read_lock(&resource_lock); > + > + for (p = prev_resource(NULL, first_level_children_only); p; > + p = prev_resource(p, first_level_children_only)) { > + if ((p->flags & res->flags) != res->flags) > + continue; > + if ((desc != IORES_DESC_NONE) && (desc != p->desc)) > + continue; > + if (p->end < res->start) { > + p = NULL; > + break; > + } > + if ((p->end >= res->start) && (p->start < res->end)) > + break; > + } > + > + read_unlock(&resource_lock); > + if (!p) > + return -1; > + /* copy data */ > + resource_clip(res, p->start, p->end); > + res->flags = p->flags; > + res->desc = p->desc; > + return 0; > +} > + > static int __walk_iomem_res_desc(struct resource *res, unsigned long desc, > bool first_level_children_only, > void *arg, > @@ -422,6 +495,27 @@ static int __walk_iomem_res_desc(struct resource *res, unsigned long desc, > return ret; > } > > +static int __walk_iomem_res_rev_desc(struct resource *res, unsigned long desc, > + bool first_level_children_only, > + void *arg, > + int (*func)(struct resource *, void *)) > +{ > + u64 orig_start = res->start; > + int ret = -1; > + > + while ((res->start < res->end) && > + !find_prev_iomem_res(res, desc, first_level_children_only)) { > + ret = (*func)(res, arg); > + if (ret) > + break; > + > + res->end = res->start - 1; > + res->start = orig_start; > + } > + > + return ret; > +} > + > /* > * Walks through iomem resources and calls func() with matching resource > * ranges. This walks through whole tree and not just first level children. > @@ -468,6 +562,25 @@ int walk_system_ram_res(u64 start, u64 end, void *arg, > arg, func); > } > > +/* > + * This function, being a variant of walk_system_ram_res(), calls the @func > + * callback against all memory ranges of type System RAM which are marked as > + * IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY in reversed order, i.e., from > + * higher to lower. > + */ > +int walk_system_ram_res_rev(u64 start, u64 end, void *arg, > + int (*func)(struct resource *, void *)) > +{ > + struct resource res; > + > + res.start = start; > + res.end = end; > + res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; > + > + return __walk_iomem_res_rev_desc(&res, IORES_DESC_NONE, true, > + arg, func); > +} > + > /* > * This function calls the @func callback against all memory ranges, which > * are ranges marked as IORESOURCE_MEM and IORESOUCE_BUSY. > -- > 2.15.1 > > > -- > Wei Yang > Help you, Help me _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
