From bb90d4bc7b6a536b2e4db45f4763e467c2008251 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 9 Feb 2021 22:22:14 -0800 Subject: [PATCH 1/6] mm/highmem: Lift memcpy_[to|from]_page to core Working through a conversion to a call kmap_local_page() instead of kmap() revealed many places where the pattern kmap/memcpy/kunmap occurred. Eric Biggers, Matthew Wilcox, Christoph Hellwig, Dan Williams, and Al Viro all suggested putting this code into helper functions. Al Viro further pointed out that these functions already existed in the iov_iter code.[1] Various locations for the lifted functions were considered. Headers like mm.h or string.h seem ok but don't really portray the functionality well. pagemap.h made some sense but is for page cache functionality.[2] Another alternative would be to create a new header for the promoted memcpy functions, but it masks the fact that these are designed to copy to/from pages using the kernel direct mappings and complicates matters with a new header. Placing these functions in 'highmem.h' is suboptimal especially with the changes being proposed in the functionality of kmap. From a caller perspective including/using 'highmem.h' implies that the functions defined in that header are only required when highmem is in use which is increasingly not the case with modern processors. However, highmem.h is where all the current functions like this reside (zero_user(), clear_highpage(), clear_user_highpage(), copy_user_highpage(), and copy_highpage()). So it makes the most sense even though it is distasteful for some.[3] Lift memcpy_to_page() and memcpy_from_page() to pagemap.h. [1] https://lore.kernel.org/lkml/20201013200149.GI3576660@ZenIV.linux.org.uk/ https://lore.kernel.org/lkml/20201013112544.GA5249@infradead.org/ [2] https://lore.kernel.org/lkml/20201208122316.GH7338@casper.infradead.org/ [3] https://lore.kernel.org/lkml/20201013200149.GI3576660@ZenIV.linux.org.uk/#t https://lore.kernel.org/lkml/20201208163814.GN1563847@iweiny-DESK2.sc.intel.com/ Cc: Boris Pismenny Cc: Or Gerlitz Cc: Dave Hansen Suggested-by: Matthew Wilcox Suggested-by: Christoph Hellwig Suggested-by: Dan Williams Suggested-by: Al Viro Suggested-by: Eric Biggers Reviewed-by: Chaitanya Kulkarni Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Signed-off-by: David Sterba --- include/linux/highmem.h | 18 ++++++++++++++++++ lib/iov_iter.c | 14 -------------- 2 files changed, 18 insertions(+), 14 deletions(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index d2c70d3772a3d..736b6a9f144d7 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -276,4 +276,22 @@ static inline void copy_highpage(struct page *to, struct page *from) #endif +static inline void memcpy_from_page(char *to, struct page *page, + size_t offset, size_t len) +{ + char *from = kmap_atomic(page); + + memcpy(to, from + offset, len); + kunmap_atomic(from); +} + +static inline void memcpy_to_page(struct page *page, size_t offset, + const char *from, size_t len) +{ + char *to = kmap_atomic(page); + + memcpy(to + offset, from, len); + kunmap_atomic(to); +} + #endif /* _LINUX_HIGHMEM_H */ diff --git a/lib/iov_iter.c b/lib/iov_iter.c index a21e6a5792c5a..9889e9903cdf3 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -466,20 +466,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, } EXPORT_SYMBOL(iov_iter_init); -static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len) -{ - char *from = kmap_atomic(page); - memcpy(to, from + offset, len); - kunmap_atomic(from); -} - -static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len) -{ - char *to = kmap_atomic(page); - memcpy(to + offset, from, len); - kunmap_atomic(to); -} - static void memzero_page(struct page *page, size_t offset, size_t len) { char *addr = kmap_atomic(page); From 61b205f579911a11f0b576f73275eca2aed0d108 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 9 Feb 2021 22:22:15 -0800 Subject: [PATCH 2/6] mm/highmem: Convert memcpy_[to|from]_page() to kmap_local_page() kmap_local_page() is more efficient and is well suited for these calls. Convert the kmap() to kmap_local_page() Cc: Andrew Morton Cc: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Signed-off-by: David Sterba --- include/linux/highmem.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 736b6a9f144d7..c17a175fe5fe2 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -279,19 +279,19 @@ static inline void copy_highpage(struct page *to, struct page *from) static inline void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len) { - char *from = kmap_atomic(page); + char *from = kmap_local_page(page); memcpy(to, from + offset, len); - kunmap_atomic(from); + kunmap_local(from); } static inline void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len) { - char *to = kmap_atomic(page); + char *to = kmap_local_page(page); memcpy(to + offset, from, len); - kunmap_atomic(to); + kunmap_local(to); } #endif /* _LINUX_HIGHMEM_H */ From 6a0996db6879cf09f989c5f44f9edd38240cb346 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 9 Feb 2021 22:22:16 -0800 Subject: [PATCH 3/6] mm/highmem: Introduce memcpy_page(), memmove_page(), and memset_page() 3 more common kmap patterns are kmap/memcpy/kunmap, kmap/memmove/kunmap. and kmap/memset/kunmap. Add helper functions for those patterns which use kmap_local_page(). Cc: Andrew Morton Cc: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Signed-off-by: David Sterba --- include/linux/highmem.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index c17a175fe5fe2..0b5d89621cb95 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -276,6 +276,39 @@ static inline void copy_highpage(struct page *to, struct page *from) #endif +static inline void memcpy_page(struct page *dst_page, size_t dst_off, + struct page *src_page, size_t src_off, + size_t len) +{ + char *dst = kmap_local_page(dst_page); + char *src = kmap_local_page(src_page); + + memcpy(dst + dst_off, src + src_off, len); + kunmap_local(src); + kunmap_local(dst); +} + +static inline void memmove_page(struct page *dst_page, size_t dst_off, + struct page *src_page, size_t src_off, + size_t len) +{ + char *dst = kmap_local_page(dst_page); + char *src = kmap_local_page(src_page); + + memmove(dst + dst_off, src + src_off, len); + kunmap_local(src); + kunmap_local(dst); +} + +static inline void memset_page(struct page *page, size_t offset, int val, + size_t len) +{ + char *addr = kmap_local_page(page); + + memset(addr + offset, val, len); + kunmap_local(addr); +} + static inline void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len) { From ca18f6ea012bf30236b76c3480ac2c97131b6f8f Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Wed, 10 Feb 2021 09:49:28 -0800 Subject: [PATCH 4/6] mm/highmem: Add VM_BUG_ON() to mem*_page() calls Add VM_BUG_ON bounds checks to ensure the newly lifted and created page memory operations do not result in corrupted data in neighbor pages.[1][2] [1] https://lore.kernel.org/lkml/20201210053502.GS1563847@iweiny-DESK2.sc.intel.com/ [2] https://lore.kernel.org/lkml/20210209110931.00f00e47d9a0529fcee2ff01@linux-foundation.org/ Suggested-by: Matthew Wilcox Suggested-by: Andrew Morton Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Signed-off-by: David Sterba --- include/linux/highmem.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 0b5d89621cb95..44170f312ae76 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -283,6 +283,7 @@ static inline void memcpy_page(struct page *dst_page, size_t dst_off, char *dst = kmap_local_page(dst_page); char *src = kmap_local_page(src_page); + VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); memcpy(dst + dst_off, src + src_off, len); kunmap_local(src); kunmap_local(dst); @@ -295,6 +296,7 @@ static inline void memmove_page(struct page *dst_page, size_t dst_off, char *dst = kmap_local_page(dst_page); char *src = kmap_local_page(src_page); + VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); memmove(dst + dst_off, src + src_off, len); kunmap_local(src); kunmap_local(dst); @@ -305,6 +307,7 @@ static inline void memset_page(struct page *page, size_t offset, int val, { char *addr = kmap_local_page(page); + VM_BUG_ON(offset + len > PAGE_SIZE); memset(addr + offset, val, len); kunmap_local(addr); } @@ -314,6 +317,7 @@ static inline void memcpy_from_page(char *to, struct page *page, { char *from = kmap_local_page(page); + VM_BUG_ON(offset + len > PAGE_SIZE); memcpy(to, from + offset, len); kunmap_local(from); } @@ -323,6 +327,7 @@ static inline void memcpy_to_page(struct page *page, size_t offset, { char *to = kmap_local_page(page); + VM_BUG_ON(offset + len > PAGE_SIZE); memcpy(to + offset, from, len); kunmap_local(to); } From 3590ec58991bcf0f3512c4353a786079a6619758 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 9 Feb 2021 22:22:19 -0800 Subject: [PATCH 5/6] btrfs: use memcpy_[to|from]_page() and kmap_local_page() There are many places where the pattern kmap/memcpy/kunmap occurs. This pattern was lifted to the core common functions memcpy_[to|from]_page(). Use these new functions to reduce the code, eliminate direct uses of kmap, and leverage the new core functions use of kmap_local_page(). Also, there is 1 place where a kmap/memcpy is followed by an optional memset. Here we leave the kmap open coded to avoid remapping the page but use kmap_local_page() directly. Development of this patch was aided by the coccinelle script: // // SPDX-License-Identifier: GPL-2.0-only // Find kmap/memcpy/kunmap pattern and replace with memcpy*page calls // // NOTE: Offsets and other expressions may be more complex than what the script // will automatically generate. Therefore a catchall rule is provided to find // the pattern which then must be evaluated by hand. // // Confidence: Low // Copyright: (C) 2021 Intel Corporation // URL: http://coccinelle.lip6.fr/ // Comments: // Options: // // simple memcpy version // @ memcpy_rule1 @ expression page, T, F, B, Off; identifier ptr; type VP; @@ ( -VP ptr = kmap(page); | -ptr = kmap(page); | -VP ptr = kmap_atomic(page); | -ptr = kmap_atomic(page); ) <+... ( -memcpy(ptr + Off, F, B); +memcpy_to_page(page, Off, F, B); | -memcpy(ptr, F, B); +memcpy_to_page(page, 0, F, B); | -memcpy(T, ptr + Off, B); +memcpy_from_page(T, page, Off, B); | -memcpy(T, ptr, B); +memcpy_from_page(T, page, 0, B); ) ...+> ( -kunmap(page); | -kunmap_atomic(ptr); ) // Remove any pointers left unused @ depends on memcpy_rule1 @ identifier memcpy_rule1.ptr; type VP, VP1; @@ -VP ptr; ... when != ptr; ? VP1 ptr; // // Some callers kmap without a temp pointer // @ memcpy_rule2 @ expression page, T, Off, F, B; @@ <+... ( -memcpy(kmap(page) + Off, F, B); +memcpy_to_page(page, Off, F, B); | -memcpy(kmap(page), F, B); +memcpy_to_page(page, 0, F, B); | -memcpy(T, kmap(page) + Off, B); +memcpy_from_page(T, page, Off, B); | -memcpy(T, kmap(page), B); +memcpy_from_page(T, page, 0, B); ) ...+> -kunmap(page); // No need for the ptr variable removal // // Catch all // @ memcpy_rule3 @ expression page; expression GenTo, GenFrom, GenSize; identifier ptr; type VP; @@ ( -VP ptr = kmap(page); | -ptr = kmap(page); | -VP ptr = kmap_atomic(page); | -ptr = kmap_atomic(page); ) <+... ( // // Some call sites have complex expressions within the memcpy // match a catch all to be evaluated by hand. // -memcpy(GenTo, GenFrom, GenSize); +memcpy_to_pageExtra(page, GenTo, GenFrom, GenSize); +memcpy_from_pageExtra(GenTo, page, GenFrom, GenSize); ) ...+> ( -kunmap(page); | -kunmap_atomic(ptr); ) // Remove any pointers left unused @ depends on memcpy_rule3 @ identifier memcpy_rule3.ptr; type VP, VP1; @@ -VP ptr; ... when != ptr; ? VP1 ptr; // Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/compression.c | 6 ++---- fs/btrfs/lzo.c | 4 ++-- fs/btrfs/reflink.c | 6 +----- fs/btrfs/send.c | 7 ++----- fs/btrfs/zlib.c | 5 ++--- fs/btrfs/zstd.c | 6 ++---- 6 files changed, 11 insertions(+), 23 deletions(-) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 5ae3fa0386b76..047b632b4139f 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -1231,7 +1231,6 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, unsigned long prev_start_byte; unsigned long working_bytes = total_out - buf_start; unsigned long bytes; - char *kaddr; struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter); /* @@ -1262,9 +1261,8 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, PAGE_SIZE - (buf_offset % PAGE_SIZE)); bytes = min(bytes, working_bytes); - kaddr = kmap_atomic(bvec.bv_page); - memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes); - kunmap_atomic(kaddr); + memcpy_to_page(bvec.bv_page, bvec.bv_offset, buf + buf_offset, + bytes); flush_dcache_page(bvec.bv_page); buf_offset += bytes; diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c index aa9cd11f4b78b..9084a950dc091 100644 --- a/fs/btrfs/lzo.c +++ b/fs/btrfs/lzo.c @@ -467,7 +467,7 @@ int lzo_decompress(struct list_head *ws, unsigned char *data_in, destlen = min_t(unsigned long, destlen, PAGE_SIZE); bytes = min_t(unsigned long, destlen, out_len - start_byte); - kaddr = kmap_atomic(dest_page); + kaddr = kmap_local_page(dest_page); memcpy(kaddr, workspace->buf + start_byte, bytes); /* @@ -477,7 +477,7 @@ int lzo_decompress(struct list_head *ws, unsigned char *data_in, */ if (bytes < destlen) memset(kaddr+bytes, 0, destlen-bytes); - kunmap_atomic(kaddr); + kunmap_local(kaddr); out: return ret; } diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c index b03e7891394e3..74c62e49c0c99 100644 --- a/fs/btrfs/reflink.c +++ b/fs/btrfs/reflink.c @@ -103,12 +103,8 @@ static int copy_inline_to_page(struct btrfs_inode *inode, set_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &inode->runtime_flags); if (comp_type == BTRFS_COMPRESS_NONE) { - char *map; - - map = kmap(page); - memcpy(map, data_start, datal); + memcpy_to_page(page, 0, data_start, datal); flush_dcache_page(page); - kunmap(page); } else { ret = btrfs_decompress(comp_type, data_start, page, 0, inline_size, datal); diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 78a35374d4929..83982b3b70572 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -4948,7 +4948,6 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len) struct btrfs_fs_info *fs_info = root->fs_info; struct inode *inode; struct page *page; - char *addr; pgoff_t index = offset >> PAGE_SHIFT; pgoff_t last_index; unsigned pg_offset = offset_in_page(offset); @@ -5001,10 +5000,8 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len) } } - addr = kmap(page); - memcpy(sctx->send_buf + sctx->send_size, addr + pg_offset, - cur_len); - kunmap(page); + memcpy_from_page(sctx->send_buf + sctx->send_size, page, + pg_offset, cur_len); unlock_page(page); put_page(page); index++; diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c index 05615a1099dbc..d524acf7b3e57 100644 --- a/fs/btrfs/zlib.c +++ b/fs/btrfs/zlib.c @@ -432,9 +432,8 @@ int zlib_decompress(struct list_head *ws, unsigned char *data_in, PAGE_SIZE - (buf_offset % PAGE_SIZE)); bytes = min(bytes, bytes_left); - kaddr = kmap_atomic(dest_page); - memcpy(kaddr + pg_offset, workspace->buf + buf_offset, bytes); - kunmap_atomic(kaddr); + memcpy_to_page(dest_page, pg_offset, + workspace->buf + buf_offset, bytes); pg_offset += bytes; bytes_left -= bytes; diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c index 9a4871636c6c7..8e9626d639763 100644 --- a/fs/btrfs/zstd.c +++ b/fs/btrfs/zstd.c @@ -688,10 +688,8 @@ int zstd_decompress(struct list_head *ws, unsigned char *data_in, bytes = min_t(unsigned long, destlen - pg_offset, workspace->out_buf.size - buf_offset); - kaddr = kmap_atomic(dest_page); - memcpy(kaddr + pg_offset, workspace->out_buf.dst + buf_offset, - bytes); - kunmap_atomic(kaddr); + memcpy_to_page(dest_page, pg_offset, + workspace->out_buf.dst + buf_offset, bytes); pg_offset += bytes; } From 80cc83842394e5ad3e93487359106aab3420bcb7 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 9 Feb 2021 22:22:20 -0800 Subject: [PATCH 6/6] btrfs: use copy_highpage() instead of 2 kmaps() There are many places where kmap/memove/kunmap patterns occur. This pattern exists in the core common function copy_highpage(). Use copy_highpage to avoid open coding the use of kmap and leverages the core functions use of kmap_local_page(). Development of this patch was aided by the following coccinelle script: // // SPDX-License-Identifier: GPL-2.0-only // Find kmap/copypage/kunmap pattern and replace with copy_highpage calls // // NOTE: The expressions in the copy page version of this kmap pattern are // overly complex and so these all need individual attention. // // Confidence: Low // Copyright: (C) 2021 Intel Corporation // URL: http://coccinelle.lip6.fr/ // Comments: // Options: // // Then a copy_page where we have 2 pages involved. // @ copy_page_rule @ expression page, page2, To, From, Size; identifier ptr, ptr2; type VP, VP2; @@ /* kmap */ ( -VP ptr = kmap(page); ... -VP2 ptr2 = kmap(page2); | -VP ptr = kmap_atomic(page); ... -VP2 ptr2 = kmap_atomic(page2); | -ptr = kmap(page); ... -ptr2 = kmap(page2); | -ptr = kmap_atomic(page); ... -ptr2 = kmap_atomic(page2); ) // 1 or more copy versions of the entire page <+... ( -copy_page(To, From); +copy_highpage(To, From); | -memmove(To, From, Size); +memmoveExtra(To, From, Size); ) ...+> /* kunmap */ ( -kunmap(page2); ... -kunmap(page); | -kunmap(page); ... -kunmap(page2); | -kmap_atomic(ptr2); ... -kmap_atomic(ptr); ) // Remove any pointers left unused @ depends on copy_page_rule @ identifier copy_page_rule.ptr; identifier copy_page_rule.ptr2; type VP, VP1; type VP2, VP21; @@ -VP ptr; ... when != ptr; ? VP1 ptr; -VP2 ptr2; ... when != ptr2; ? VP21 ptr2; // Reviewed-by: Christoph Hellwig Signed-off-by: Ira Weiny Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/raid56.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c index 93fbf87bdc8d3..c86aff9c7daa0 100644 --- a/fs/btrfs/raid56.c +++ b/fs/btrfs/raid56.c @@ -250,8 +250,6 @@ int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info) static void cache_rbio_pages(struct btrfs_raid_bio *rbio) { int i; - char *s; - char *d; int ret; ret = alloc_rbio_pages(rbio); @@ -262,13 +260,7 @@ static void cache_rbio_pages(struct btrfs_raid_bio *rbio) if (!rbio->bio_pages[i]) continue; - s = kmap(rbio->bio_pages[i]); - d = kmap(rbio->stripe_pages[i]); - - copy_page(d, s); - - kunmap(rbio->bio_pages[i]); - kunmap(rbio->stripe_pages[i]); + copy_highpage(rbio->stripe_pages[i], rbio->bio_pages[i]); SetPageUptodate(rbio->stripe_pages[i]); } set_bit(RBIO_CACHE_READY_BIT, &rbio->flags);