kernel/linux.git/fs/btrfs/zlib.c, branch linux-6.0.y

btrfs: zlib: replace kmap() with kmap_local_page() in zlib_decompress_bio()

2022-07-25T15:45:41+00:00

The use of kmap() is being deprecated in favor of kmap_local_page(). With kmap_local_page(), the mapping is per thread, CPU local and not globally visible. Therefore, use kmap_local_page() / kunmap_local() in zlib_decompress_bio() because in this function the mappings are per thread and are not visible in other contexts. Tested with xfstests on QEMU + KVM 32-bits VM with 4GB of RAM and HIGHMEM64G enabled. This patch passes 26/26 tests of group "compress". Suggested-by: Ira Weiny Reviewed-by: Ira Weiny Reviewed-by: Qu Wenruo Signed-off-by: Fabio M. De Francesco Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: zlib: replace kmap() with kmap_local_page() in zlib_compress_pages()

2022-07-25T15:45:40+00:00

The use of kmap() is being deprecated in favor of kmap_local_page(). With kmap_local_page(), the mapping is per thread, CPU local and not globally visible. Therefore, use kmap_local_page() / kunmap_local() in zlib_compress_pages() because in this function the mappings are per thread and are not visible in other contexts. Furthermore, drop the mappings of "out_page" which is allocated within zlib_compress_pages() with alloc_page(GFP_NOFS) and use page_address(). Tested with xfstests on a QEMU + KVM 32-bits VM with 4GB of RAM booting a kernel with HIGHMEM64G enabled. This patch passes 26/26 tests of group "compress". CC: Qu Wenruo Suggested-by: Ira Weiny Reviewed-by: Ira Weiny Signed-off-by: Fabio M. De Francesco Reviewed-by: David Sterba Signed-off-by: David Sterba

Revert "btrfs: compression: drop kmap/kunmap from zlib"

2021-10-29T11:03:05+00:00

This reverts commit 696ab562e6df9fbafd6052d8ce4aafcb2ed16069. The kmaps in compression code are still needed and cause crashes on 32bit machines (ARM, x86). Reproducible eg. by running fstest btrfs/004 with enabled LZO or ZSTD compression. Link: https://lore.kernel.org/all/CAJCQCtT+OuemovPO7GZk8Y8=qtOObr0XTDp8jh4OHD6y84AFxw@mail.gmail.com/ Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214839 Signed-off-by: David Sterba

btrfs: rework btrfs_decompress_buf2page()

2021-08-23T11:19:04+00:00

There are several bugs inside the function btrfs_decompress_buf2page() - @start_byte doesn't take bvec.bv_offset into consideration Thus it can't handle case where the target range is not page aligned. - Too many helper variables There are tons of helper variables, @buf_offset, @current_buf_start, @start_byte, @prev_start_byte, @working_bytes, @bytes. This hurts anyone who wants to read the function. - No obvious main cursor for the iteartion A new problem caused by previous problem. - Comments for parameter list makes no sense Like @buf_start is the offset to @buf, or offset inside the full decompressed extent? (Spoiler alert, the later case) And @total_out acts more like @buf_start + @size_of_buf. The worst is @disk_start. The real meaning of it is the file offset of the full decompressed extent. This patch will rework the whole function by: - Add a proper comment with ASCII art to explain the parameter list - Rework parameter list The old @buf_start is renamed to @decompressed, to show how many bytes are already decompressed inside the full decompressed extent. The old @total_out is replaced by @buf_len, which is the decompressed data size. For old @disk_start and @bio, just pass @compressed_bio in. - Use single main cursor The main cursor will be @cur_file_offset, to show what's the current file offset. Other helper variables will be declared inside the main loop, and only minimal amount of helper variables: * offset_inside_decompressed_buf: The only real helper * copy_start_file_offset: File offset we start memcpy * bvec_file_offset: File offset of current bvec Even with all these extensive comments, the final function is still smaller than the original function, which is definitely a win. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: compression: drop kmap/kunmap from zlib

2021-08-23T11:18:59+00:00

As we don't use highmem pages anymore, drop the kmap/kunmap. The kmap is simply page_address and kunmap is a no-op. Signed-off-by: David Sterba

btrfs: drop from __GFP_HIGHMEM all allocations

2021-08-23T11:18:59+00:00

The highmem flag is used for allocating pages for compression and for raid56 pages. The high memory makes sense on 32bit systems but is not without problems. On 64bit system's it's just another layer of wrappers. The time the pages are allocated for compression or raid56 is relatively short (about a transaction commit), so the pages are not blocked indefinitely. As the number of pages depends on the amount of data being written/read, there's a theoretical problem. A fast device on a 32bit system could use most of the low memory pool, while with the highmem allocation that would not happen. This was possibly the original idea long time ago, but nowadays we optimize for 64bit systems. This patch removes all usage of the __GFP_HIGHMEM flag for page allocation, the kmap/kunmap are still in place and will be removed in followup patches. Remaining is masking out the bit in alloc_extent_state and __lookup_free_space_inode, that can safely stay. Signed-off-by: David Sterba

btrfs: use memzero_page() instead of open coded kmap pattern

2021-05-05T18:27:27+00:00

There are many places where kmap/memset/kunmap patterns occur. Use the newly lifted memzero_page() to eliminate direct uses of kmap and leverage the new core functions use of kmap_local_page(). The development of this patch was aided by the following coccinelle script: // // SPDX-License-Identifier: GPL-2.0-only // Find kmap/memset/kunmap pattern and replace with memset*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: // // Then the memset pattern // @ memset_rule1 @ expression page, V, L, Off; identifier ptr; type VP; @@ ( -VP ptr = kmap(page); | -ptr = kmap(page); | -VP ptr = kmap_atomic(page); | -ptr = kmap_atomic(page); ) <+... ( -memset(ptr, 0, L); +memzero_page(page, 0, L); | -memset(ptr + Off, 0, L); +memzero_page(page, Off, L); | -memset(ptr, V, L); +memset_page(page, V, 0, L); | -memset(ptr + Off, V, L); +memset_page(page, V, Off, L); ) ...+> ( -kunmap(page); | -kunmap_atomic(ptr); ) // Remove any pointers left unused @ depends on memset_rule1 @ identifier memset_rule1.ptr; type VP, VP1; @@ -VP ptr; ... when != ptr; ? VP1 ptr; // // Catch all // @ memset_rule2 @ expression page; identifier ptr; expression GenTo, GenSize, GenValue; 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 memset/memcpy // The follow are catch alls which need to be evaluated by hand. // -memset(GenTo, 0, GenSize); +memzero_pageExtra(page, GenTo, GenSize); | -memset(GenTo, GenValue, GenSize); +memset_pageExtra(page, GenValue, GenTo, GenSize); ) ...+> ( -kunmap(page); | -kunmap_atomic(ptr); ) // Remove any pointers left unused @ depends on memset_rule2 @ identifier memset_rule2.ptr; type VP, VP1; @@ -VP ptr; ... when != ptr; ? VP1 ptr; // Link: https://lkml.kernel.org/r/20210309212137.2610186-4-ira.weiny@intel.com Signed-off-by: Ira Weiny Reviewed-by: David Sterba Cc: Alexander Viro Cc: Chaitanya Kulkarni Cc: Chris Mason Cc: Josef Bacik Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

btrfs: use memcpy_[to|from]_page() and kmap_local_page()

2021-02-26T11:45:15+00:00

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

btrfs: use larger zlib buffer for s390 hardware compression

2020-01-31T18:30:40+00:00

In order to benefit from s390 zlib hardware compression support, increase the btrfs zlib workspace buffer size from 1 to 4 pages (if s390 zlib hardware support is enabled on the machine). This brings up to 60% better performance in hardware on s390 compared to the PAGE_SIZE buffer and much more compared to the software zlib processing in btrfs. In case of memory pressure, fall back to a single page buffer during workspace allocation. The data compressed with larger input buffers will still conform to zlib standard and thus can be decompressed also on a systems that uses only PAGE_SIZE buffer for btrfs zlib. Link: http://lkml.kernel.org/r/20200108105103.29028-1-zaslonko@linux.ibm.com Signed-off-by: Mikhail Zaslonko Reviewed-by: David Sterba Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba Cc: Richard Purdie Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Eduard Shishkin Cc: Ilya Leoshkevich Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

btrfs: compression: inline free_workspace

2019-11-18T11:46:59+00:00

Replace indirect calls to free_workspace by switch and calls to the specific callbacks. This is mainly to get rid of the indirection due to spectre vulnerability mitigations. Reviewed-by: Johannes Thumshirn Reviewed-by: Nikolay Borisov Signed-off-by: David Sterba