Squashfs: Update squashfs_readahead() to not use page->index

This commit removes references to page->index in the pages returned
from __readahead_batch(), and instead uses the 'start' variable.

This does reveal a bug in the previous code in that 'start' was
not updated every time around the loop.  This is fixed in this
commit.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Link: https://lore.kernel.org/r/20240818235847.170468-3-phillip@squashfs.org.uk
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index 2b6b63f4ccd1a19189a45fdb4844b05b7aa58fbc..50fe5a078b831c21a84a788ab565c9ae5d85e80d 100644 (file)
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -551,7 +551,6 @@ static void squashfs_readahead(struct readahead_control *ractl)
                return;
 
        for (;;) {
-               pgoff_t index;
                int res, bsize;
                u64 block = 0;
                unsigned int expected;
@@ -570,13 +569,8 @@ static void squashfs_readahead(struct readahead_control *ractl)
                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;
-
-               if (index == file_end && squashfs_i(inode)->fragment_block !=
-                                               SQUASHFS_INVALID_BLK) {
+               if (start >> msblk->block_log == file_end &&
+                               squashfs_i(inode)->fragment_block != SQUASHFS_INVALID_BLK) {
                        res = squashfs_readahead_fragment(pages, nr_pages,
                                                          expected);
                        if (res)
@@ -584,7 +578,7 @@ static void squashfs_readahead(struct readahead_control *ractl)
                        continue;
                }
 
-               bsize = read_blocklist(inode, index, &block);
+               bsize = read_blocklist(inode, start >> msblk->block_log, &block);
                if (bsize == 0)
                        goto skip_pages;
 
@@ -602,7 +596,7 @@ static void squashfs_readahead(struct readahead_control *ractl)
 
                        /* Last page (if present) may have trailing bytes not filled */
                        bytes = res % PAGE_SIZE;
-                       if (index == file_end && bytes && last_page)
+                       if (start >> msblk->block_log == file_end && bytes && last_page)
                                memzero_page(last_page, bytes,
                                             PAGE_SIZE - bytes);
 
@@ -616,6 +610,8 @@ static void squashfs_readahead(struct readahead_control *ractl)
                        unlock_page(pages[i]);
                        put_page(pages[i]);
                }
+
+               start += readahead_batch_length(ractl);
        }
 
        kfree(pages);