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[87.17.106.94]) by smtp.gmail.com with ESMTPSA id g12-20020a056402114c00b004404e290e7esm6854178edw.77.2022.08.21.11.10.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 Aug 2022 11:11:00 -0700 (PDT) From: "Fabio M. De Francesco" To: Ira Weiny , "Matthew Wilcox (Oracle)" , Jens Axboe , Bart Van Assche , Christian Brauner , Andrew Morton , Kees Cook , Jeff Layton , Damien Le Moal , Arnd Bergmann , Roman Gushchin , Muchun Song , Chaitanya Kulkarni , "Martin K. Petersen" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: "Fabio M. De Francesco" , Viacheslav Dubeyko Subject: [RESEND PATCH 4/4] hfsplus: Convert kmap() to kmap_local_page() in btree.c Date: Sun, 21 Aug 2022 20:10:45 +0200 Message-Id: <20220821181045.8528-5-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220821181045.8528-1-fmdefrancesco@gmail.com> References: <20220821181045.8528-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org kmap() is being deprecated in favor of kmap_local_page(). There are 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 are still valid. Since its use in btree.c is safe everywhere, it should be preferred. Therefore, replace kmap() with kmap_local_page() in btree.c. Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with HIGHMEM64GB enabled. Cc: Viacheslav Dubeyko Suggested-by: Ira Weiny Reviewed-by: Ira Weiny Reviewed-by: Viacheslav Dubeyko Signed-off-by: Fabio M. De Francesco --- fs/hfsplus/btree.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c index 3a917a9a4edd..9e1732a2b92a 100644 --- a/fs/hfsplus/btree.c +++ b/fs/hfsplus/btree.c @@ -163,7 +163,7 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id) goto free_inode; /* Load the header */ - head = (struct hfs_btree_header_rec *)(kmap(page) + + head = (struct hfs_btree_header_rec *)(kmap_local_page(page) + sizeof(struct hfs_bnode_desc)); tree->root = be32_to_cpu(head->root); tree->leaf_count = be32_to_cpu(head->leaf_count); @@ -240,12 +240,12 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id) (tree->node_size + PAGE_SIZE - 1) >> PAGE_SHIFT; - kunmap(page); + kunmap_local(head); put_page(page); return tree; fail_page: - kunmap(page); + kunmap_local(head); put_page(page); free_inode: tree->inode->i_mapping->a_ops = &hfsplus_aops; @@ -292,7 +292,7 @@ int hfs_btree_write(struct hfs_btree *tree) return -EIO; /* Load the header */ page = node->page[0]; - head = (struct hfs_btree_header_rec *)(kmap(page) + + head = (struct hfs_btree_header_rec *)(kmap_local_page(page) + sizeof(struct hfs_bnode_desc)); head->root = cpu_to_be32(tree->root); @@ -304,7 +304,7 @@ int hfs_btree_write(struct hfs_btree *tree) head->attributes = cpu_to_be32(tree->attributes); head->depth = cpu_to_be16(tree->depth); - kunmap(page); + kunmap_local(head); set_page_dirty(page); hfs_bnode_put(node); return 0; @@ -395,7 +395,7 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree) off += node->page_offset; pagep = node->page + (off >> PAGE_SHIFT); - data = kmap(*pagep); + data = kmap_local_page(*pagep); off &= ~PAGE_MASK; idx = 0; @@ -408,7 +408,7 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree) idx += i; data[off] |= m; set_page_dirty(*pagep); - kunmap(*pagep); + kunmap_local(data); tree->free_nodes--; mark_inode_dirty(tree->inode); hfs_bnode_put(node); @@ -418,14 +418,14 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree) } } if (++off >= PAGE_SIZE) { - kunmap(*pagep); - data = kmap(*++pagep); + kunmap_local(data); + data = kmap_local_page(*++pagep); off = 0; } idx += 8; len--; } - kunmap(*pagep); + kunmap_local(data); nidx = node->next; if (!nidx) { hfs_dbg(BNODE_MOD, "create new bmap node\n"); @@ -441,7 +441,7 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree) off = off16; off += node->page_offset; pagep = node->page + (off >> PAGE_SHIFT); - data = kmap(*pagep); + data = kmap_local_page(*pagep); off &= ~PAGE_MASK; } } @@ -491,7 +491,7 @@ void hfs_bmap_free(struct hfs_bnode *node) } off += node->page_offset + nidx / 8; page = node->page[off >> PAGE_SHIFT]; - data = kmap(page); + data = kmap_local_page(page); off &= ~PAGE_MASK; m = 1 << (~nidx & 7); byte = data[off]; @@ -499,13 +499,13 @@ void hfs_bmap_free(struct hfs_bnode *node) pr_crit("trying to free free bnode " "%u(%d)\n", node->this, node->type); - kunmap(page); + kunmap_local(data); hfs_bnode_put(node); return; } data[off] = byte & ~m; set_page_dirty(page); - kunmap(page); + kunmap_local(data); hfs_bnode_put(node); tree->free_nodes++; mark_inode_dirty(tree->inode);