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UPSTREAM: squashfs: fix extending readahead beyond end of file

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The readahead code will try to extend readahead to the entire size of the
Squashfs data block.

But, it didn't take into account that the last block at the end of the
file may not be a whole block.  In this case, the code would extend
readahead to beyond the end of the file, leaving trailing pages.

Fix this by only requesting the expected number of pages.

Link: https://lkml.kernel.org/r/20221020223616.7571-3-phillip@squashfs.org.uk
Fixes: 8fc78b6fe24c ("squashfs: implement readahead")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reported-by: Marc Miltenberger <marcmiltenberger@gmail.com>
Cc: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc: Slade Watkins <srw@sladewatkins.net>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: <stable@vger.kernel.org>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Bug: 290900323
(cherry picked from commit c9199de82bad03bceb94ec3c5195c879d7e11911)
Change-Id: Ic2d449471ab6caa8acbde2eba48b781d47ad0e2a
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
This commit is contained in:
Phillip Lougher
2022-10-20 23:36:15 +01:00
committed by Lecopzer Chen
parent c194120949
commit 9d967debc7
1 changed files with 7 additions and 4 deletions
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11
fs/squashfs/file.c
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@@ -557,6 +557,12 @@ static void squashfs_readahead(struct readahead_control *ractl)
unsigned int expected;
struct page *last_page;
expected = start >> msblk->block_log == file_end ?
(i_size_read(inode) & (msblk->block_size - 1)) :
msblk->block_size;
max_pages = (expected + PAGE_SIZE - 1) >> PAGE_SHIFT;
nr_pages = __readahead_batch(ractl, pages, max_pages);
if (!nr_pages)
break;
@@ -565,13 +571,10 @@ static void squashfs_readahead(struct readahead_control *ractl)
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;
if (index == file_end && squashfs_i(inode)->fragment_block !=
SQUASHFS_INVALID_BLK) {
res = squashfs_readahead_fragment(pages, nr_pages,