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fs: clear or set FMODE_LSEEK based on llseek function

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Pipe-like behaviour on llseek(2) (i.e. unconditionally failing with
-ESPIPE) can be expresses in 3 ways:
	1) ->llseek set to NULL in file_operations
	2) ->llseek set to no_llseek in file_operations
	3) FMODE_LSEEK *not* set in ->f_mode.

Enforce (3) in cases (1) and (2); that will allow to simplify the
checks and eventually get rid of no_llseek boilerplate.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jason A. Donenfeld 2022-06-29 15:06:57 +02:00 • committed by Al Viro
parent b13baccc38
commit e7478158e1
2 changed files with 6 additions and 0 deletions
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4
fs/open.c
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@ -858,6 +858,10 @@ static int do_dentry_open(struct file *f,
if ((f->f_mode & FMODE_WRITE) &&
likely(f->f_op->write || f->f_op->write_iter))
f->f_mode |= FMODE_CAN_WRITE;
if ((f->f_mode & FMODE_LSEEK) && !f->f_op->llseek)
f->f_mode &= ~FMODE_LSEEK;
if ((f->f_mode & FMODE_LSEEK) && f->f_op->llseek == no_llseek)
f->f_mode &= ~FMODE_LSEEK;
if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO)
f->f_mode |= FMODE_CAN_ODIRECT;