add late free dictionary for f2fs decompression and some optimizations · Pull Request !121 · openEuler/kernel

Because the decompression needs to be performed when reading the compressed block, and the space of the dictionary needs to be released after the decompression is completed to reduce the space occupation caused by the decompression. In some cases, when we read and decompress the cluster, other tasks are using the current dictionary, so the space of the dictionary should not be released immediately, but the dictionary should be released when no tasks refer to the current dictionary.
This patch Add dictionary delayed release function.
in compress.c : 
    add `f2fs_late_free_dic` function ： Lazy free dictionary during read。
    Added in_task parameter：add in_tack parameter in some function, such as f2fs_decompress_cluster, `f2fs_decompress_end_io`, `f2fs_put_dic` eg.
    Modify the f2fs_read_end_io function to determine whether a task is in progress when reading data:
        When intask() is true:
            1. The current execution context is not in the NMI context;
            2. Not in IRQ context;
            3. Not in softirq context Chinese;
Other optimizations: 
1. Compression judgment logic of the cache array: When the compression process initializes the page array cache, add the judgment of whether the current file system super block has the compression function to prevent the wrong logical path: Add the judgment of f2fs_sb_has_compression in the f2fs_init_page_array_cache function;
2. Consistency check when writing back cache pages: In the f2fs_all_cluster_page_ready function, after checking whether all pages in the cluster are loaded, you need to try to check whether all pages in the cluster are up-to-date.
    1. When uptodate is set to true, try to check that all pages in the cluster are up to date.
    2. When writing back the cachepage from the disk, the old data of the cached page may be inconsistent with the current decompression dictionary, resulting in a decompression error.

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