fs: move permission hook out of do_iter_read()

fs: move permission hook out of do_iter_read()

We recently moved fsnotify hook, rw_verify_area() and other checks from
do_iter_write() out to its two callers.

for consistency, do the same thing for do_iter_read() - move the
rw_verify_area() checks and fsnotify hook to the callers vfs_iter_read()
and vfs_readv().

This aligns those vfs helpers with the pattern used in vfs_read() and
vfs_iocb_iter_read() and the vfs write helpers, where all the checks are
in the vfs helpers and the do_* or call_* helpers do the work.

This is needed for fanotify "pre content" events.

Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231122122715.2561213-13-amir73il@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>