Squashfs: add additional inode sanity checking

Squashfs: add additional inode sanity checking

[ Upstream commit 9ee94bfbe930a1b39df53fa2d7b31141b780eb5a ]

Patch series "Squashfs: performance improvement and a sanity check".

This patchset adds an additional sanity check when reading regular file
inodes, and adds support for SEEK_DATA/SEEK_HOLE lseek() whence values.

This patch (of 2):

Add an additional sanity check when reading regular file inodes.

A regular file if the file size is an exact multiple of the filesystem
block size cannot have a fragment.  This is because by definition a
fragment block stores tailends which are not a whole block in size.

Link: https://lkml.kernel.org/r/20250923220652.568416-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20250923220652.568416-2-phillip@squashfs.org.uk
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 9f1c14c1de1b ("Squashfs: reject negative file sizes in squashfs_read_inode()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>