[Crash-utility] Re: [PATCH v8 2/3] xarray: add large folio support

Thanks for all the improvements. LGTM, ack for the patchset. Thanks, Tao Liu On Mon, May 18, 2026 at 11:38 PM Huang Shijie <huangsj(a)hygon.cn&gt; wrote: > > We may meet a large folio at two cases: > 1.) when height is 1, the real data layout may looks like this: > -------------------------------------------- > crash> p *(struct xa_node*)0xffff889883a6a910 > $5 = { > shift = 0 '\000', > offset = 0 '\000', > count = 64 '@', > nr_values = 0 '\000', > ................. > slots = { 0xffffea0061d21000, 0x2, 0x2, 0x2, > 0xffffea0121d85c00, 0x12, 0x12, 0x12, > 0xffffea0121d9f400, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, > 0xffffea0121583800, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, > 0xffffea0121833e00, 0x62, 0x62, 0x62, 0x62, 0x62, 0x62, 0x62, > 0xffffea0121eb3800, 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, > 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, > 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, > 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, 0x82, > 0x82, 0x82, 0x82 > }, > ................. > } > -------------------------------------------- > The page orders for above folios: > 0xffffea0061d21000 --> order 2 > 0xffffea0121d85c00 --> order 2 > 0xffffea0121d9f400 --> order 3 > 0xffffea0121583800 --> order 3 > 0xffffea0121833e00 --> order 3 > 0xffffea0121eb3800 --> order 5 > > 2.) when height is not 1, the real data layout may looks like this: > -------------------------------------------- > slot: { 0xffff8a2c866b745a, 0xffff8a2c866b16d2, 0xfffff9fcc4ea4000, 0xfffff9fcc4eb9000, ..} > -------------------------------------------- > The 0xffff8a2c866b745a and 0xffff8a2c866b16d2 is a internal node, not a folio. > The page orders for above folios: > 0xfffff9fcc4ea4000 --> order 6 > > Current code does not work correctly with large folio page cache. > This patch adds the large folio support with following: > > 1.) Add XARRAY_TYPE_PAGE_CACHE flag for do_xarray(). > 2.) Add update_count hook for do_xarray_info{}, > add update_off hook for xarray_ops{}. > 3.) changed the do_xarray_iter() to check the update_off > at proper place (height == 1 and height > 1). > 4.) Implement the folio_update_count/folio_xarray_update_off > hooks for large folio page cache. > > Signed-off-by: Huang Shijie <huangsj(a)hygon.cn&gt; > --- > defs.h | 5 +++++ > filesys.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++----- > tools.c | 15 +++++++++++++-- > 3 files changed, 64 insertions(+), 7 deletions(-) > > diff --git a/defs.h b/defs.h > index bd996ef..e7e97e7 100644 > --- a/defs.h > +++ b/defs.h > @@ -5689,6 +5689,9 @@ int do_radix_tree_traverse(ulong ptr, int is_root, struct radix_tree_ops *ops); > struct xarray_ops { > void (*entry)(ulong node, ulong slot, const char *path, > ulong index, void *private); > + uint (*update_off)(ulong node, uint height, char *path, ulong index, > + ulong slot, uint off, ulong shift, struct xarray_ops *ops, > + bool *should_continue); > uint radix; > void *private; > }; > @@ -6003,6 +6006,8 @@ ulong do_xarray(ulong, int, struct list_pair *); > #define XARRAY_DUMP_CB (5) > #define XARRAY_TAG_MASK (3UL) > #define XARRAY_TAG_INTERNAL (2UL) > +#define XARRAY_TYPE_PAGE_CACHE 0x8 > +extern ulong XA_CHUNK_SHIFT; > > int folio_order(ulong folio); > > diff --git a/filesys.c b/filesys.c > index 34944e2..35d55a5 100644 > --- a/filesys.c > +++ b/filesys.c > @@ -2289,7 +2289,7 @@ dump_inode_page_cache_info(ulong inode) > if (root_rnode) > count = do_radix_tree(root_rnode, RADIX_TREE_DUMP_CB, &lp); > else if (xarray) > - count = do_xarray(xarray, XARRAY_DUMP_CB, &lp); > + count = do_xarray(xarray, XARRAY_DUMP_CB | XARRAY_TYPE_PAGE_CACHE, &lp); > > if (count != nrpages) > error(INFO, "%s page count: %ld nrpages: %ld\n", > @@ -4217,12 +4217,46 @@ struct do_xarray_info { > ulong maxcount; > ulong count; > void *data; > + ulong (*update_count)(ulong); > }; > + > +static ulong > +folio_update_count(ulong slot) > +{ > + return 1 << folio_order(slot); > +} > + > +static uint folio_xarray_update_off(ulong node, uint height, char *path, ulong index, > + ulong slot, uint off, ulong shift, struct xarray_ops *ops, bool *should_continue) > +{ > + uint order; > + > + *should_continue = false; > + > + if (height == 1) { > + order = folio_order(slot) % XA_CHUNK_SHIFT; > + return 1 << order; > + } > + > + /* height > 1 */ > + if ((slot & XARRAY_TAG_MASK) == 0) { > + ops->entry(node, slot, path, index | off, ops->private); > + *should_continue = true; > + order = folio_order(slot) % XA_CHUNK_SHIFT; > + return 1 << order; > + } > + return 1; > +} > + > static void do_xarray_count(ulong node, ulong slot, const char *path, > ulong index, void *private) > { > struct do_xarray_info *info = private; > - info->count++; > + > + if (info->update_count) > + info->count += info->update_count(slot); > + else > + info->count++; > } > static void do_xarray_search(ulong node, ulong slot, const char *path, > ulong index, void *private) > @@ -4239,8 +4273,9 @@ static void do_xarray_dump(ulong node, ulong slot, const char *path, > ulong index, void *private) > { > struct do_xarray_info *info = private; > + > fprintf(fp, "[%ld] %lx\n", index, slot); > - info->count++; > + do_xarray_count(node, slot, path, index, private); > } > static void do_xarray_gather(ulong node, ulong slot, const char *path, > ulong index, void *private) > @@ -4274,7 +4309,8 @@ static void do_xarray_dump_cb(ulong node, ulong slot, const char *path, > "operation failed: entry: %ld item: %lx\n", > info->count, slot); > } > - info->count++; > + > + do_xarray_count(node, slot, path, index, private); > } > > /* > @@ -4318,7 +4354,12 @@ do_xarray(ulong root, int flag, struct list_pair *xp) > .private = &info, > }; > > - switch (flag) > + if (flag & XARRAY_TYPE_PAGE_CACHE) { > + info.update_count = folio_update_count; > + ops.update_off = folio_xarray_update_off; > + } > + > + switch (flag & 0x7) > { > case XARRAY_COUNT: > ops.entry = do_xarray_count; > diff --git a/tools.c b/tools.c > index 69250c4..7dc11ae 100644 > --- a/tools.c > +++ b/tools.c > @@ -4728,7 +4728,7 @@ error_height: > return -1; > } > > -static ulong XA_CHUNK_SHIFT = UNINITIALIZED; > +ulong XA_CHUNK_SHIFT = UNINITIALIZED; > static ulong XA_CHUNK_SIZE = UNINITIALIZED; > static ulong XA_CHUNK_MASK = UNINITIALIZED; > > @@ -4737,21 +4737,32 @@ do_xarray_iter(ulong node, uint height, char *path, > ulong index, struct xarray_ops *ops) > { > uint off; > + uint update_off; > + bool should_continue; > > if (!hq_enter(node)) > error(FATAL, > "\nduplicate tree node: %lx\n", node); > > - for (off = 0; off < XA_CHUNK_SIZE; off++) { > + for (off = 0; off < XA_CHUNK_SIZE; off += update_off) { > ulong slot; > ulong shift = (height - 1) * XA_CHUNK_SHIFT; > > + update_off = 1; > + > readmem(node + OFFSET(xa_node_slots) + > sizeof(void *) * off, KVADDR, &slot, sizeof(void *), > "xa_node.slots[off]", FAULT_ON_ERROR); > if (!slot) > continue; > > + if (ops->update_off) { > + update_off = ops->update_off(node, height, path, index, > + slot, off, shift, ops, &should_continue); > + if (should_continue) > + continue; > + } > + > if ((slot & XARRAY_TAG_MASK) == XARRAY_TAG_INTERNAL) > slot &= ~XARRAY_TAG_INTERNAL; > > -- > 2.53.0 > > > >