#
835cd826 |
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22-Jan-2024 |
Colin Ian King <colin.i.king@gmail.com> |
btrfs: zlib: Fix spelling mistake "infalte" -> "inflate" There is a spelling mistake in a warning message. Fix it. Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
2c25716d |
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08-Jan-2024 |
Qu Wenruo <wqu@suse.com> |
btrfs: zlib: fix and simplify the inline extent decompression [BUG] If we have a filesystem with 4k sectorsize, and an inlined compressed extent created like this: item 4 key (257 INODE_ITEM 0) itemoff 15863 itemsize 160 generation 8 transid 8 size 4096 nbytes 4096 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 1 flags 0x0(none) item 5 key (257 INODE_REF 256) itemoff 15839 itemsize 24 index 2 namelen 14 name: source_inlined item 6 key (257 EXTENT_DATA 0) itemoff 15770 itemsize 69 generation 8 type 0 (inline) inline extent data size 48 ram_bytes 4096 compression 1 (zlib) Which has an inline compressed extent at file offset 0, and its decompressed size is 4K, allowing us to reflink that 4K range to another location (which will not be compressed). If we do such reflink on a subpage system, it would fail like this: # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest XFS_IOC_CLONE_RANGE: Input/output error [CAUSE] In zlib_decompress(), we didn't treat @start_byte as just a page offset, but also use it as an indicator on whether we should switch our output buffer. In reality, for subpage cases, although @start_byte can be non-zero, we should never switch input/output buffer, since the whole input/output buffer should never exceed one sector. Note: The above assumption is only not true if we're going to support multi-page sectorsize. Thus the current code using @start_byte as a condition to switch input/output buffer or finish the decompression is completely incorrect. [FIX] The fix involves several modifications: - Rename @start_byte to @dest_pgoff to properly express its meaning - Add an extra ASSERT() inside btrfs_decompress() to make sure the input/output size never exceeds one sector. - Use Z_FINISH flag to make sure the decompression happens in one go - Remove the loop needed to switch input/output buffers - Use correct destination offset inside the destination page - Consider early end as an error After the fix, even on 64K page sized aarch64, above reflink now works as expected: # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest linked 4096/4096 bytes at offset 61440 And resulted a correct file layout: item 9 key (258 INODE_ITEM 0) itemoff 15542 itemsize 160 generation 10 transid 10 size 65536 nbytes 4096 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 1 flags 0x0(none) item 10 key (258 INODE_REF 256) itemoff 15528 itemsize 14 index 3 namelen 4 name: dest item 11 key (258 XATTR_ITEM 3817753667) itemoff 15445 itemsize 83 location key (0 UNKNOWN.0 0) type XATTR transid 10 data_len 37 name_len 16 name: security.selinux data unconfined_u:object_r:unlabeled_t:s0 item 12 key (258 EXTENT_DATA 61440) itemoff 15392 itemsize 53 generation 10 type 1 (regular) extent data disk byte 13631488 nr 4096 extent data offset 0 nr 4096 ram 4096 extent compression 0 (none) Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
9ba965dc |
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15-Nov-2023 |
David Sterba <dsterba@suse.com> |
btrfs: use page alloc/free wrappers for compression pages This is a preparation for managing compression pages in a cache-like manner, instead of asking the allocator each time. The common allocation and free wrappers are introduced and are functionally equivalent to the current code. The freeing helpers need to be carefully placed where the last reference is dropped. This is either after directly allocating (error handling) or when there are no other users of the pages (after copying the contents). It's safe to not use the helper and use put_page() that will handle the reference count. Not using the helper means there's lower number of pages that could be reused without passing them back to allocator. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
8ab546bb |
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22-May-2023 |
David Sterba <dsterba@suse.com> |
btrfs: disable allocation warnings for compression workspaces The workspaces for compression are typically much larger than a page and for high zstd levels in the range of megabytes. There's a fallback to vmalloc but this can still fail (see the report). Some of the workspaces are preallocated at module load time so we have a safe fallback, otherwise when a new workspace is needed it's allocated but if this fails then the process waits. Which means the warning is only causing noise and we can use the GFP flag to disable it. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217466 Signed-off-by: David Sterba <dsterba@suse.com>
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#
7edb9a3e |
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07-Mar-2023 |
Christoph Hellwig <hch@lst.de> |
btrfs: move zero filling of compressed read bios into common code All algorithms have to fill the remainder of the orig_bio with zeroes, so do it in common code. Reviewed-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: David Sterba <dsterba@suse.com>
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#
eadd7dec |
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23-Jan-2023 |
Alexander Potapenko <glider@google.com> |
btrfs: zlib: zero-initialize zlib workspace KMSAN reports uses of uninitialized memory in zlib's longest_match() called on memory originating from zlib_alloc_workspace(). This issue is known by zlib maintainers and is claimed to be harmless, but to be on the safe side we'd better initialize the memory. Link: https://zlib.net/zlib_faq.html#faq36 Reported-by: syzbot+14d9e7602ebdf7ec0a60@syzkaller.appspotmail.com CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Alexander Potapenko <glider@google.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
3e09b5b2 |
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07-Nov-2022 |
David Sterba <dsterba@suse.com> |
btrfs: constify input buffer parameter in compression code The input buffers passed down to compression must never be changed, switch type to u8 as it's a raw byte buffer and use const. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
9e5e6d4e |
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31-Oct-2022 |
David Sterba <dsterba@suse.com> |
btrfs: zlib: use copy_page for full page copy The copy_page helper may use an optimized version for full page copy (eg. on s390 there's a special instruction for that), there's one more left to convert. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
5a6e6e7c |
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18-Jun-2022 |
Fabio M. De Francesco <fmdefrancesco@gmail.com> |
btrfs: zlib: replace kmap() with kmap_local_page() in zlib_decompress_bio() 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 <ira.weiny@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
718e5855 |
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27-Jun-2022 |
Fabio M. De Francesco <fmdefrancesco@gmail.com> |
btrfs: zlib: replace kmap() with kmap_local_page() in zlib_compress_pages() 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 <wqu@suse.com> Suggested-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
55276e14 |
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27-Oct-2021 |
David Sterba <dsterba@suse.com> |
Revert "btrfs: compression: drop kmap/kunmap from zlib" 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 <dsterba@suse.com>
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#
1c3dc173 |
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04-Jul-2021 |
Qu Wenruo <wqu@suse.com> |
btrfs: rework btrfs_decompress_buf2page() 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 <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
696ab562 |
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14-Jun-2021 |
David Sterba <dsterba@suse.com> |
btrfs: compression: drop kmap/kunmap from zlib 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 <dsterba@suse.com>
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#
b0ee5e1e |
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14-Jun-2021 |
David Sterba <dsterba@suse.com> |
btrfs: drop from __GFP_HIGHMEM all allocations 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 <dsterba@suse.com>
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#
d048b9c2 |
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04-May-2021 |
Ira Weiny <ira.weiny@intel.com> |
btrfs: use memzero_page() instead of open coded kmap pattern 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: // <smpl> // 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; // </smpl> Link: https://lkml.kernel.org/r/20210309212137.2610186-4-ira.weiny@intel.com Signed-off-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: David Sterba <dsterba@suse.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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#
3590ec58 |
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09-Feb-2021 |
Ira Weiny <ira.weiny@intel.com> |
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: // <smpl> // 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; // <smpl> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
3fd396af |
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30-Jan-2020 |
Mikhail Zaslonko <zaslonko@linux.ibm.com> |
btrfs: use larger zlib buffer for s390 hardware compression 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 <zaslonko@linux.ibm.com> Reviewed-by: David Sterba <dsterba@suse.com> Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <josef@toxicpanda.com> Cc: David Sterba <dsterba@suse.com> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Eduard Shishkin <edward6@linux.ibm.com> Cc: Ilya Leoshkevich <iii@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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#
1e002351 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline free_workspace 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 <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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c778df14 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline alloc_workspace Replace indirect calls to alloc_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 <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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5907a9bb |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: pass type to btrfs_get_workspace We can infer the workspace_manager from type and the type will be used in the following patch to call a common helper for alloc_workspace. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
bd3a5287 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline put_workspace Similar to get_workspace, majority of the callbacks is trivial, we don't gain anything by the indirection, so replace them by a switch function. Trivial callback implementations use the helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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6a0d1272 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline get_workspace Majority of the callbacks is trivial, we don't gain anything by the indirection, so replace them by a switch function. ZLIB needs to adjust level in the callback and ZSTD workspace management is complex, the rest is call to the helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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d20f395f |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: export alloc/free/get/put callbacks of all algos The indirect calls will be replaced by a switch in compression.c. (Switch is faster than indirect calls with when Spectre mitigations are enabled). Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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2510307e |
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01-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline cleanup_workspace_manager Replace loop calling to all algos with a list of direct calls to the cleanup manager callback. When that becomes trivial it is replaced by direct call to the helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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2dba7143 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: let workspace manager cleanup take only the type With the access to the workspace structures, we can look it up together with the compression ops inside the workspace manager cleanup helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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d5517033 |
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01-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: inline init_workspace_manager Replace loop calling to all algos with a list of direct calls to the init manager callback. When that becomes trivial it is replaced by direct call to the helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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975db483 |
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03-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: let workspace manager init take only the type With the access to the workspace structures, we can look it up together with the compression ops inside the workspace manager init helper. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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be951045 |
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01-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: attach workspace manager to the ops There's a lot of indirection when the generic code calls into algo-specific callbacks to reach the private workspace manager structure and back to the generic code. To simplify that, export the workspace manager for heuristic, LZO and ZLIB, while ZSTD is going to use it's own manager. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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1e4eb746 |
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01-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: switch compression callbacks to direct calls The indirect calls bring some overhead due to spectre vulnerability mitigations. The number of cases is small and below the threshold (10-20) where indirect call would be better. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
c4bf665a |
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01-Oct-2019 |
David Sterba <dsterba@suse.com> |
btrfs: export compression and decompression callbacks Export compress_pages, decompress_bio and decompress callbacks for all compression algos. The indirect calls will be replaced by a switch. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
b0c1fe1e |
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09-Aug-2019 |
David Sterba <dsterba@suse.com> |
btrfs: compression: replace set_level callbacks by a common helper The set_level callbacks do not do anything special and can be replaced by a helper that uses the levels defined in the tables. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
e18333a7 |
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09-Aug-2019 |
David Sterba <dsterba@suse.com> |
btrfs: define compression levels statically The maximum and default levels do not change and can be defined directly. The set_level callback was a temporary solution and will be removed. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
d0ab62ce |
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04-Feb-2019 |
Dennis Zhou <dennis@kernel.org> |
btrfs: change set_level() to bound the level passed in Currently, the only user of set_level() is zlib which sets an internal workspace parameter. As level is now plumbed into get_workspace(), this can be handled there rather than separately. This repurposes set_level() to bound the level passed in so it can be used when setting the mounts compression level and as well as verifying the level before getting a workspace. The other benefit is this divides the meaning of compress(0) and get_workspace(0). The former means we want to use the default compression level of the compression type. The latter means we can use any workspace available. Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
7bf49943 |
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04-Feb-2019 |
Dennis Zhou <dennis@kernel.org> |
btrfs: plumb level through the compression interface Zlib compression supports multiple levels, but doesn't require changing in how a workspace itself is created and managed. Zstd introduces a different memory requirement such that higher levels of compression require more memory. This requires changes in how the alloc()/get() methods work for zstd. This pach plumbs compression level through the interface as a parameter in preparation for zstd compression levels. This gives the compression types opportunity to create/manage based on the compression level. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
92ee5530 |
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04-Feb-2019 |
Dennis Zhou <dennis@kernel.org> |
btrfs: move to function pointers for get/put workspaces The previous patch added generic helpers for get_workspace() and put_workspace(). Now, we can migrate ownership of the workspace_manager to be in the compression type code as the compression code itself doesn't care beyond being able to get a workspace. The init/cleanup and get/put methods are abstracted so each compression algorithm can decide how they want to manage their workspaces. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
1972708a |
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04-Feb-2019 |
Dennis Zhou <dennis@kernel.org> |
btrfs: add helpers for compression type and level It is very easy to miss places that rely on a certain bitshifting for decoding the type_level overloading. Add helpers to do this instead. Cc: Omar Sandoval <osandov@osandov.com> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
c1d7c514 |
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03-Apr-2018 |
David Sterba <dsterba@suse.com> |
btrfs: replace GPL boilerplate by SPDX -- sources Remove GPL boilerplate text (long, short, one-line) and keep the rest, ie. personal, company or original source copyright statements. Add the SPDX header. Signed-off-by: David Sterba <dsterba@suse.com>
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#
f51d2b59 |
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15-Sep-2017 |
David Sterba <dsterba@suse.com> |
btrfs: allow to set compression level for zlib Preliminary support for setting compression level for zlib, the following works: $ mount -o compess=zlib # default $ mount -o compess=zlib0 # same $ mount -o compess=zlib9 # level 9, slower sync, less data $ mount -o compess=zlib1 # level 1, faster sync, more data $ mount -o remount,compress=zlib3 # level set by remount The compress-force works the same as compress'. The level is visible in the same format in /proc/mounts. Level set via file property does not work yet. Required patch: "btrfs: prepare for extensions in compression options" Signed-off-by: David Sterba <dsterba@suse.com>
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#
6acafd1e |
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31-May-2017 |
David Sterba <dsterba@suse.com> |
btrfs: switch to kvmalloc and GFP_KERNEL in lzo/zlib alloc_workspace The compression workspace buffers are larger than a page so we use vmalloc, unconditionally. This is not always necessary as there might be contiguous memory available. Let's use the kvmalloc helpers that will try kmalloc first and fallback to vmalloc. For that they require GFP_KERNEL flags. As we now have the alloc_workspace calls protected by memalloc_nofs in the critical contexts, we can safely use GFP_KERNEL. Signed-off-by: David Sterba <dsterba@suse.com>
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#
389a6cfc |
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31-May-2017 |
David Sterba <dsterba@suse.com> |
btrfs: switch kmallocs to GFP_KERNEL in lzo/zlib alloc_workspace As alloc_workspace is now protected by memalloc_nofs where needed, we can switch the kmalloc to use GFP_KERNEL. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
e1ddce71 |
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26-May-2017 |
Anand Jain <anand.jain@oracle.com> |
btrfs: reduce arguments for decompress_bio ops struct compressed_bio pointer can be used instead. Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
e5d74902 |
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14-Feb-2017 |
David Sterba <dsterba@suse.com> |
btrfs: derive maximum output size in the compression implementation The value of max_out can be calculated from the parameters passed to the compressors, which is number of pages and the page size, and we don't have to needlessly pass it around. Signed-off-by: David Sterba <dsterba@suse.com>
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#
4d3a800e |
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14-Feb-2017 |
David Sterba <dsterba@suse.com> |
btrfs: merge nr_pages input and output parameter in compress_pages The parameter saying how many pages can be allocated at maximum can be merged with the output page counter, to save some stack space. The compression implementation will sink the parameter to a local variable so everything works as before. The nr_pages variables can also be simply merged in compress_file_range into one. Signed-off-by: David Sterba <dsterba@suse.com>
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#
38c31464 |
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14-Feb-2017 |
David Sterba <dsterba@suse.com> |
btrfs: merge length input and output parameter in compress_pages The length parameter is basically duplicated for input and output in the top level caller of the compress_pages chain. We can simply use one variable for that and reduce stack consumption. The compression implementation will sink the parameter to a local variable so everything works as before. Signed-off-by: David Sterba <dsterba@suse.com>
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#
974b1adc |
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25-Nov-2016 |
Christoph Hellwig <hch@lst.de> |
btrfs: use bio iterators for the decompression handlers Pass the full bio to the decompression routines and use bio iterators to iterate over the data in the bio. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: David Sterba <dsterba@suse.com>
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#
d1111a75 |
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01-Nov-2016 |
Nick Terrell <nickrterrell@gmail.com> |
btrfs: Call kunmap if zlib_inflateInit2 fails If zlib_inflateInit2 fails, the input page is never unmapped. Add a call to kunmap when it fails. Signed-off-by: Nick Terrell <nickrterrell@gmail.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
62e85577 |
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20-Sep-2016 |
Jeff Mahoney <jeffm@suse.com> |
btrfs: convert printk(KERN_* to use pr_* calls This patch converts printk(KERN_* style messages to use the pr_* versions. One side effect is that anything that was KERN_DEBUG is now automatically a dynamic debug message. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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#
09cbfeaf |
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01-Apr-2016 |
Kirill A. Shutemov <kirill.shutemov@linux.intel.com> |
mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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#
e8c9f186 |
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02-Jan-2015 |
David Sterba <dsterba@suse.cz> |
btrfs: constify structs with op functions or static definitions There are some op tables that can be easily made const, similarly the sysfs feature and raid tables. This is motivated by PaX CONSTIFY plugin. Signed-off-by: David Sterba <dsterba@suse.cz>
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#
2f19cad9 |
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30-Nov-2014 |
Chris Mason <clm@fb.com> |
btrfs: zero out left over bytes after processing compression streams Don Bailey noticed that our page zeroing for compression at end-io time isn't complete. This reworks a patch from Linus to push the zeroing into the zlib and lzo specific functions instead of trying to handle the corners inside btrfs_decompress_buf2page Signed-off-by: Chris Mason <clm@fb.com> Reviewed-by: Josef Bacik <jbacik@fb.com> Reported-by: Don A. Bailey <donb@securitymouse.com> cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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#
78809913 |
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07-Jul-2014 |
Sergey Senozhatsky <sergey.senozhatsky@gmail.com> |
btrfs compression: merge inflate and deflate z_streams `struct workspace' used for zlib compression contains two zlib z_stream-s: `def_strm' used in zlib_compress_pages(), and `inf_strm' used in zlib_decompress/zlib_decompress_biovec(). None of these functions use `inf_strm' and `def_strm' simultaniously, meaning that for every compress/decompress operation we need only one z_stream (out of two available). `inf_strm' and `def_strm' are different in size of ->workspace. For inflate stream we vmalloc() zlib_inflate_workspacesize() bytes, for deflate stream - zlib_deflate_workspacesize() bytes. On my system zlib returns the following workspace sizes, correspondingly: 42312 and 268104 (+ guard pages). Keep only one `z_stream' in `struct workspace' and use it for both compression and decompression. Hence, instead of vmalloc() of two z_stream->worskpace-s, allocate only one of size: max(zlib_deflate_workspacesize(), zlib_inflate_workspacesize()) Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Chris Mason <clm@fb.com>
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#
ed6078f7 |
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04-Jun-2014 |
David Sterba <dsterba@suse.cz> |
btrfs: use DIV_ROUND_UP instead of open-coded variants The form (value + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT is equivalent to (value + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE The rest is a simple subsitution, no difference in the generated assembly code. Signed-off-by: David Sterba <dsterba@suse.cz> Signed-off-by: Chris Mason <clm@fb.com>
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#
130d5b41 |
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20-Jun-2014 |
David Sterba <dsterba@suse.cz> |
btrfs: use E2BIG instead of EIO if compression does not help Return codes got updated in 60e1975acb48fc3d74a3422b21dde74c977ac3d5 (btrfs: return errno instead of -1 from compression) lzo wrapper returns E2BIG in this case, do the same for zlib. Signed-off-by: David Sterba <dsterba@suse.cz>
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#
60e1975a |
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09-May-2014 |
Zach Brown <zab@redhat.com> |
btrfs: return errno instead of -1 from compression The compression layer seems to have been built to return -1 and have callers make up errors that make sense. This isn't great because there are different errors that originate down in the compression layer. Let's return real negative errnos from the compression layer so that callers can pass on the error without having to guess what happened. ENOMEM for allocation failure, E2BIG when compression exceeds the uncompressed input, and EIO for everything else. This helps a future path return errors from btrfs_decompress(). Signed-off-by: Zach Brown <zab@redhat.com> Signed-off-by: Chris Mason <clm@fb.com>
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#
efe120a0 |
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20-Dec-2013 |
Frank Holton <fholton@gmail.com> |
Btrfs: convert printk to btrfs_ and fix BTRFS prefix Convert all applicable cases of printk and pr_* to the btrfs_* macros. Fix all uses of the BTRFS prefix. Signed-off-by: Frank Holton <fholton@gmail.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
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#
48940662 |
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07-May-2012 |
Daniel J Blueman <daniel@quora.org> |
btrfs: fix message printing Fix various messages to include newline and module prefix. Signed-off-by: Daniel J Blueman <daniel@quora.org>
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#
7ac687d9 |
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25-Nov-2011 |
Cong Wang <amwang@redhat.com> |
btrfs: remove the second argument of k[un]map_atomic() Signed-off-by: Cong Wang <amwang@redhat.com>
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#
565d76cb |
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22-Mar-2011 |
Jim Keniston <jkenisto@linux.vnet.ibm.com> |
zlib: slim down zlib_deflate() workspace when possible Instead of always creating a huge (268K) deflate_workspace with the maximum compression parameters (windowBits=15, memLevel=8), allow the caller to obtain a smaller workspace by specifying smaller parameter values. For example, when capturing oops and panic reports to a medium with limited capacity, such as NVRAM, compression may be the only way to capture the whole report. In this case, a small workspace (24K works fine) is a win, whether you allocate the workspace when you need it (i.e., during an oops or panic) or at boot time. I've verified that this patch works with all accepted values of windowBits (positive and negative), memLevel, and compression level. Signed-off-by: Jim Keniston <jkenisto@us.ibm.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David Miller <davem@davemloft.net> Cc: Chris Mason <chris.mason@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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#
3a39c18d |
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08-Nov-2010 |
Li Zefan <lizf@cn.fujitsu.com> |
btrfs: Extract duplicate decompress code Add a common function to copy decompressed data from working buffer to bio pages. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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#
261507a0 |
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16-Dec-2010 |
Li Zefan <lizf@cn.fujitsu.com> |
btrfs: Allow to add new compression algorithm Make the code aware of compression type, instead of always assuming zlib compression. Also make the zlib workspace function as common code for all compression types. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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#
4b72029d |
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08-Nov-2010 |
Li Zefan <lizf@cn.fujitsu.com> |
btrfs: Fix error handling in zlib Return failure if alloc_page() fails to allocate memory, and the upper code will just give up compression. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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#
8844355d |
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25-Oct-2010 |
Li Zefan <lizf@cn.fujitsu.com> |
btrfs: Fix bugs in zlib workspace - Fix a race that can result in alloc_workspace > cpus. - Fix to check num_workspace after wakeup. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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#
559af821 |
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29-Oct-2010 |
Andi Kleen <andi@firstfloor.org> |
Btrfs: cleanup warnings from gcc 4.6 (nonbugs) These are all the cases where a variable is set, but not read which are not bugs as far as I can see, but simply leftovers. Still needs more review. Found by gcc 4.6's new warnings Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Chris Mason <chris.mason@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Chris Mason <chris.mason@oracle.com>
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#
60f2e8f8 |
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07-Aug-2009 |
Julia Lawall <julia@diku.dk> |
Btrfs: correct error-handling zlib error handling find_zlib_workspace returns an ERR_PTR value in an error case instead of NULL. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @match exists@ expression x, E; statement S1, S2; @@ x = find_zlib_workspace(...) ... when != x = E ( * if (x == NULL || ...) S1 else S2 | * if (x == NULL && ...) S1 else S2 ) // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: Chris Mason <chris.mason@oracle.com>
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#
d397712b |
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05-Jan-2009 |
Chris Mason <chris.mason@oracle.com> |
Btrfs: Fix checkpatch.pl warnings There were many, most are fixed now. struct-funcs.c generates some warnings but these are bogus. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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#
b2950863 |
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02-Dec-2008 |
Christoph Hellwig <hch@lst.de> |
Btrfs: make things static and include the right headers Shut up various sparse warnings about symbols that should be either static or have their declarations in scope. Signed-off-by: Christoph Hellwig <hch@lst.de>
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#
5b050f04 |
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11-Nov-2008 |
Chris Mason <chris.mason@oracle.com> |
Btrfs: Fix compile warnings on 32 bit machines Simple casting here and there to fix things up. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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#
771ed689 |
|
06-Nov-2008 |
Chris Mason <chris.mason@oracle.com> |
Btrfs: Optimize compressed writeback and reads When reading compressed extents, try to put pages into the page cache for any pages covered by the compressed extent that readpages didn't already preload. Add an async work queue to handle transformations at delayed allocation processing time. Right now this is just compression. The workflow is: 1) Find offsets in the file marked for delayed allocation 2) Lock the pages 3) Lock the state bits 4) Call the async delalloc code The async delalloc code clears the state lock bits and delalloc bits. It is important this happens before the range goes into the work queue because otherwise it might deadlock with other work queue items that try to lock those extent bits. The file pages are compressed, and if the compression doesn't work the pages are written back directly. An ordered work queue is used to make sure the inodes are written in the same order that pdflush or writepages sent them down. This changes extent_write_cache_pages to let the writepage function update the wbc nr_written count. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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#
c8b97818 |
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29-Oct-2008 |
Chris Mason <chris.mason@oracle.com> |
Btrfs: Add zlib compression support This is a large change for adding compression on reading and writing, both for inline and regular extents. It does some fairly large surgery to the writeback paths. Compression is off by default and enabled by mount -o compress. Even when the -o compress mount option is not used, it is possible to read compressed extents off the disk. If compression for a given set of pages fails to make them smaller, the file is flagged to avoid future compression attempts later. * While finding delalloc extents, the pages are locked before being sent down to the delalloc handler. This allows the delalloc handler to do complex things such as cleaning the pages, marking them writeback and starting IO on their behalf. * Inline extents are inserted at delalloc time now. This allows us to compress the data before inserting the inline extent, and it allows us to insert an inline extent that spans multiple pages. * All of the in-memory extent representations (extent_map.c, ordered-data.c etc) are changed to record both an in-memory size and an on disk size, as well as a flag for compression. From a disk format point of view, the extent pointers in the file are changed to record the on disk size of a given extent and some encoding flags. Space in the disk format is allocated for compression encoding, as well as encryption and a generic 'other' field. Neither the encryption or the 'other' field are currently used. In order to limit the amount of data read for a single random read in the file, the size of a compressed extent is limited to 128k. This is a software only limit, the disk format supports u64 sized compressed extents. In order to limit the ram consumed while processing extents, the uncompressed size of a compressed extent is limited to 256k. This is a software only limit and will be subject to tuning later. Checksumming is still done on compressed extents, and it is done on the uncompressed version of the data. This way additional encodings can be layered on without having to figure out which encoding to checksum. Compression happens at delalloc time, which is basically singled threaded because it is usually done by a single pdflush thread. This makes it tricky to spread the compression load across all the cpus on the box. We'll have to look at parallel pdflush walks of dirty inodes at a later time. Decompression is hooked into readpages and it does spread across CPUs nicely. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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