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1001042e54
LZ4 always reuses the decompressed buffer as its LZ77 sliding window (dynamic dictionary) for optimal performance. However, in specific cases, the output buffer may not fully contain valid page cache pages, resulting in the use of short-lived pages for temporary purposes. Due to the limited sliding window size, LZ4 shortlived bounce pages can also be reused in a sliding manner, so each bounce page can be vmapped multiple times in different relative positions by design. In order to avoiding double frees, currently, reuse counts are recorded via page refcount, but it will no longer be used as-is in the future world of Memdescs. Just maintain a lookup table to check if a shortlived page is reused. Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com> Link: https://lore.kernel.org/r/20240711053659.1364989-1-hsiangkao@linux.alibaba.com
101 lines
3.4 KiB
C
101 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2019 HUAWEI, Inc.
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* https://www.huawei.com/
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*/
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#ifndef __EROFS_FS_COMPRESS_H
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#define __EROFS_FS_COMPRESS_H
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#include "internal.h"
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struct z_erofs_decompress_req {
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struct super_block *sb;
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struct page **in, **out;
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unsigned short pageofs_in, pageofs_out;
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unsigned int inputsize, outputsize;
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unsigned int alg; /* the algorithm for decompression */
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bool inplace_io, partial_decoding, fillgaps;
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gfp_t gfp; /* allocation flags for extra temporary buffers */
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};
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struct z_erofs_decompressor {
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int (*config)(struct super_block *sb, struct erofs_super_block *dsb,
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void *data, int size);
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int (*decompress)(struct z_erofs_decompress_req *rq,
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struct page **pagepool);
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int (*init)(void);
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void (*exit)(void);
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char *name;
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};
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/* some special page->private (unsigned long, see below) */
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#define Z_EROFS_SHORTLIVED_PAGE (-1UL << 2)
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#define Z_EROFS_PREALLOCATED_PAGE (-2UL << 2)
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/*
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* For all pages in a pcluster, page->private should be one of
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* Type Last 2bits page->private
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* short-lived page 00 Z_EROFS_SHORTLIVED_PAGE
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* preallocated page (tryalloc) 00 Z_EROFS_PREALLOCATED_PAGE
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* cached/managed page 00 pointer to z_erofs_pcluster
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* online page (file-backed, 01/10/11 sub-index << 2 | count
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* some pages can be used for inplace I/O)
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*
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* page->mapping should be one of
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* Type page->mapping
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* short-lived page NULL
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* preallocated page NULL
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* cached/managed page non-NULL or NULL (invalidated/truncated page)
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* online page non-NULL
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*
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* For all managed pages, PG_private should be set with 1 extra refcount,
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* which is used for page reclaim / migration.
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*/
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/*
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* Currently, short-lived pages are pages directly from buddy system
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* with specific page->private (Z_EROFS_SHORTLIVED_PAGE).
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* In the future world of Memdescs, it should be type 0 (Misc) memory
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* which type can be checked with a new helper.
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*/
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static inline bool z_erofs_is_shortlived_page(struct page *page)
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{
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return page->private == Z_EROFS_SHORTLIVED_PAGE;
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}
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static inline bool z_erofs_put_shortlivedpage(struct page **pagepool,
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struct page *page)
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{
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if (!z_erofs_is_shortlived_page(page))
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return false;
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erofs_pagepool_add(pagepool, page);
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return true;
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}
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extern const struct z_erofs_decompressor z_erofs_lzma_decomp;
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extern const struct z_erofs_decompressor z_erofs_deflate_decomp;
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extern const struct z_erofs_decompressor z_erofs_zstd_decomp;
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extern const struct z_erofs_decompressor *z_erofs_decomp[];
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struct z_erofs_stream_dctx {
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struct z_erofs_decompress_req *rq;
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unsigned int inpages, outpages; /* # of {en,de}coded pages */
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int no, ni; /* the current {en,de}coded page # */
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unsigned int avail_out; /* remaining bytes in the decoded buffer */
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unsigned int inbuf_pos, inbuf_sz;
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/* current status of the encoded buffer */
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u8 *kin, *kout; /* buffer mapped pointers */
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void *bounce; /* bounce buffer for inplace I/Os */
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bool bounced; /* is the bounce buffer used now? */
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};
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int z_erofs_stream_switch_bufs(struct z_erofs_stream_dctx *dctx, void **dst,
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void **src, struct page **pgpl);
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int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
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unsigned int padbufsize);
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int __init z_erofs_init_decompressor(void);
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void z_erofs_exit_decompressor(void);
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#endif
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