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squashfs: implement readahead 

Implement readahead callback for squashfs.  It will read datablocks which
cover pages in readahead request.  For a few cases it will not mark page
as uptodate, including:

- file end is 0.
- zero filled blocks.
- current batch of pages isn't in the same datablock.
- decompressor error.

Otherwise pages will be marked as uptodate.  The unhandled pages will be
updated by readpage later.

Link: https://lkml.kernel.org/r/20220617083810.337573-4-hsinyi@chromium.org
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: Xiongwei Song <Xiongwei.Song@windriver.com>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hou Tao <houtao1@huawei.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: Zhang Yi <yi.zhang@huawei.com>
Cc: Zheng Liang <zhengliang6@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Hsin-Yi Wang 2022-06-17 16:38:13 +08:00 committed by akpm
parent db98b43086
commit 8fc78b6fe2
1 changed files with 91 additions and 1 deletions
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92
fs/squashfs/file.c
View File

@ -39,6 +39,7 @@
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "page_actor.h"
/*
* Locate cache slot in range [offset, index] for specified inode. If
@ -495,7 +496,96 @@ out:
return 0;
}
static void squashfs_readahead(struct readahead_control *ractl)
{
struct inode *inode = ractl->mapping->host;
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
size_t mask = (1UL << msblk->block_log) - 1;
unsigned short shift = msblk->block_log - PAGE_SHIFT;
loff_t start = readahead_pos(ractl) & ~mask;
size_t len = readahead_length(ractl) + readahead_pos(ractl) - start;
struct squashfs_page_actor *actor;
unsigned int nr_pages = 0;
struct page **pages;
int i, file_end = i_size_read(inode) >> msblk->block_log;
unsigned int max_pages = 1UL << shift;
readahead_expand(ractl, start, (len | mask) + 1);
if (file_end == 0)
return;
pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL);
if (!pages)
return;
for (;;) {
pgoff_t index;
int res, bsize;
u64 block = 0;
unsigned int expected;
nr_pages = __readahead_batch(ractl, pages, max_pages);
if (!nr_pages)
break;
if (readahead_pos(ractl) >= i_size_read(inode))
goto skip_pages;
index = pages[0]->index >> shift;
if ((pages[nr_pages - 1]->index >> shift) != index)
goto skip_pages;
expected = index == file_end ?
(i_size_read(inode) & (msblk->block_size - 1)) :
msblk->block_size;
bsize = read_blocklist(inode, index, &block);
if (bsize == 0)
goto skip_pages;
actor = squashfs_page_actor_init_special(msblk, pages, nr_pages,
expected);
if (!actor)
goto skip_pages;
res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
kfree(actor);
if (res == expected) {
int bytes;
/* Last page (if present) may have trailing bytes not filled */
bytes = res % PAGE_SIZE;
if (pages[nr_pages - 1]->index == file_end && bytes)
memzero_page(pages[nr_pages - 1], bytes,
PAGE_SIZE - bytes);
for (i = 0; i < nr_pages; i++) {
flush_dcache_page(pages[i]);
SetPageUptodate(pages[i]);
}
}
for (i = 0; i < nr_pages; i++) {
unlock_page(pages[i]);
put_page(pages[i]);
}
}
kfree(pages);
return;
skip_pages:
for (i = 0; i < nr_pages; i++) {
unlock_page(pages[i]);
put_page(pages[i]);
}
kfree(pages);
}
const struct address_space_operations squashfs_aops = {
.read_folio = squashfs_read_folio
.read_folio = squashfs_read_folio,
.readahead = squashfs_readahead
};