From ca0ac8dfd35b218b3c95d3b38c695fbff35d94ca Mon Sep 17 00:00:00 2001 From: "Fabio M. De Francesco" Date: Sun, 21 Aug 2022 20:03:59 +0200 Subject: hfs: replace kmap() with kmap_local_page() in bnode.c kmap() is being deprecated in favor of kmap_local_page(). Two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap's pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and still valid. Since its use in bnode.c is safe everywhere, it should be preferred. Therefore, replace kmap() with kmap_local_page() in bnode.c. Where possible, use the suited standard helpers (memzero_page(), memcpy_page()) instead of open coding kmap_local_page() plus memset() or memcpy(). Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with HIGHMEM64GB enabled. Link: https://lkml.kernel.org/r/20220821180400.8198-3-fmdefrancesco@gmail.com Signed-off-by: Fabio M. De Francesco Suggested-by: Ira Weiny Reviewed-by: Viacheslav Dubeyko Cc: Arnd Bergmann Cc: Chaitanya Kulkarni Cc: Christian Brauner (Microsoft) Cc: Damien Le Moal Cc: Jeff Layton Cc: Jens Axboe Cc: Kees Cook Cc: Martin K. Petersen Cc: Matthew Wilcox Cc: Muchun Song Cc: Roman Gushchin Cc: Theodore Ts'o Signed-off-by: Andrew Morton --- fs/hfs/bnode.c | 32 ++++++++++++-------------------- 1 file changed, 12 insertions(+), 20 deletions(-) (limited to 'fs/hfs') diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c index c83fd0e8404d..2015e42e752a 100644 --- a/fs/hfs/bnode.c +++ b/fs/hfs/bnode.c @@ -21,7 +21,6 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len) int pagenum; int bytes_read; int bytes_to_read; - void *vaddr; off += node->page_offset; pagenum = off >> PAGE_SHIFT; @@ -33,9 +32,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len) page = node->page[pagenum]; bytes_to_read = min_t(int, len - bytes_read, PAGE_SIZE - off); - vaddr = kmap_atomic(page); - memcpy(buf + bytes_read, vaddr + off, bytes_to_read); - kunmap_atomic(vaddr); + memcpy_from_page(buf + bytes_read, page, off, bytes_to_read); pagenum++; off = 0; /* page offset only applies to the first page */ @@ -80,8 +77,7 @@ void hfs_bnode_write(struct hfs_bnode *node, void *buf, int off, int len) off += node->page_offset; page = node->page[0]; - memcpy(kmap(page) + off, buf, len); - kunmap(page); + memcpy_to_page(page, off, buf, len); set_page_dirty(page); } @@ -105,8 +101,7 @@ void hfs_bnode_clear(struct hfs_bnode *node, int off, int len) off += node->page_offset; page = node->page[0]; - memset(kmap(page) + off, 0, len); - kunmap(page); + memzero_page(page, off, len); set_page_dirty(page); } @@ -123,9 +118,7 @@ void hfs_bnode_copy(struct hfs_bnode *dst_node, int dst, src_page = src_node->page[0]; dst_page = dst_node->page[0]; - memcpy(kmap(dst_page) + dst, kmap(src_page) + src, len); - kunmap(src_page); - kunmap(dst_page); + memcpy_page(dst_page, dst, src_page, src, len); set_page_dirty(dst_page); } @@ -140,9 +133,9 @@ void hfs_bnode_move(struct hfs_bnode *node, int dst, int src, int len) src += node->page_offset; dst += node->page_offset; page = node->page[0]; - ptr = kmap(page); + ptr = kmap_local_page(page); memmove(ptr + dst, ptr + src, len); - kunmap(page); + kunmap_local(ptr); set_page_dirty(page); } @@ -346,13 +339,14 @@ struct hfs_bnode *hfs_bnode_find(struct hfs_btree *tree, u32 num) if (!test_bit(HFS_BNODE_NEW, &node->flags)) return node; - desc = (struct hfs_bnode_desc *)(kmap(node->page[0]) + node->page_offset); + desc = (struct hfs_bnode_desc *)(kmap_local_page(node->page[0]) + + node->page_offset); node->prev = be32_to_cpu(desc->prev); node->next = be32_to_cpu(desc->next); node->num_recs = be16_to_cpu(desc->num_recs); node->type = desc->type; node->height = desc->height; - kunmap(node->page[0]); + kunmap_local(desc); switch (node->type) { case HFS_NODE_HEADER: @@ -436,14 +430,12 @@ struct hfs_bnode *hfs_bnode_create(struct hfs_btree *tree, u32 num) } pagep = node->page; - memset(kmap(*pagep) + node->page_offset, 0, - min((int)PAGE_SIZE, (int)tree->node_size)); + memzero_page(*pagep, node->page_offset, + min((int)PAGE_SIZE, (int)tree->node_size)); set_page_dirty(*pagep); - kunmap(*pagep); for (i = 1; i < tree->pages_per_bnode; i++) { - memset(kmap(*++pagep), 0, PAGE_SIZE); + memzero_page(*++pagep, 0, PAGE_SIZE); set_page_dirty(*pagep); - kunmap(*pagep); } clear_bit(HFS_BNODE_NEW, &node->flags); wake_up(&node->lock_wq); -- cgit v1.2.3-58-ga151