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squashfs: don't use intermediate buffer if pages missing

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Now that the "page actor" can handle missing pages, we don't have to fall
back to using an intermediate buffer in Squashfs_readpage_block() if all
the pages necessary can't be obtained.

Link: https://lkml.kernel.org/r/20220611032133.5743-3-phillip@squashfs.org.uk
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Xiongwei Song <Xiongwei.Song@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Phillip Lougher 2022-06-11 04:21:33 +01:00 committed by akpm
parent f268eedddf
commit 1bb1a07afa
1 changed files with 12 additions and 63 deletions
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75
fs/squashfs/file_direct.c
View File

@ -18,9 +18,6 @@
#include "squashfs.h"
#include "page_actor.h"
static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
int pages, struct page **page, int bytes);
/* Read separately compressed datablock directly into page cache */
int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
int expected)
@ -33,7 +30,7 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
int start_index = target_page->index & ~mask;
int end_index = start_index | mask;
int i, n, pages, missing_pages, bytes, res = -ENOMEM;
int i, n, pages, bytes, res = -ENOMEM;
struct page **page;
struct squashfs_page_actor *actor;
void *pageaddr;
@ -48,44 +45,29 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
return res;
/* Try to grab all the pages covered by the Squashfs block */
for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {
for (i = 0, n = start_index; n <= end_index; n++) {
page[i] = (n == target_page->index) ? target_page :
grab_cache_page_nowait(target_page->mapping, n);
if (page[i] == NULL) {
missing_pages++;
if (page[i] == NULL)
continue;
}
if (PageUptodate(page[i])) {
unlock_page(page[i]);
put_page(page[i]);
page[i] = NULL;
missing_pages++;
continue;
}
i++;
}
if (missing_pages) {
/*
* Couldn't get one or more pages, this page has either
* been VM reclaimed, but others are still in the page cache
* and uptodate, or we're racing with another thread in
* squashfs_readpage also trying to grab them. Fall back to
* using an intermediate buffer.
*/
res = squashfs_read_cache(target_page, block, bsize, pages,
page, expected);
if (res < 0)
goto mark_errored;
goto out;
}
pages = i;
/*
* Create a "page actor" which will kmap and kunmap the
* page cache pages appropriately within the decompressor
*/
actor = squashfs_page_actor_init_special(msblk, page, pages, 0);
actor = squashfs_page_actor_init_special(msblk, page, pages, expected);
if (actor == NULL)
goto out;
@ -102,12 +84,12 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
goto mark_errored;
}
/* Last page may have trailing bytes not filled */
/* Last page (if present) may have trailing bytes not filled */
bytes = res % PAGE_SIZE;
if (bytes) {
pageaddr = kmap_atomic(page[pages - 1]);
if (page[pages - 1]->index == end_index && bytes) {
pageaddr = kmap_local_page(page[pages - 1]);
memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
kunmap_atomic(pageaddr);
kunmap_local(pageaddr);
}
/* Mark pages as uptodate, unlock and release */
@ -140,36 +122,3 @@ out:
kfree(page);
return res;
}
static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
int pages, struct page **page, int bytes)
{
struct inode *i = target_page->mapping->host;
struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
block, bsize);
int res = buffer->error, n, offset = 0;
if (res) {
ERROR("Unable to read page, block %llx, size %x\n", block,
bsize);
goto out;
}
for (n = 0; n < pages && bytes > 0; n++,
bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
int avail = min_t(int, bytes, PAGE_SIZE);
if (page[n] == NULL)
continue;
squashfs_fill_page(page[n], buffer, offset, avail);
unlock_page(page[n]);
if (page[n] != target_page)
put_page(page[n]);
}
out:
squashfs_cache_put(buffer);
return res;
}