unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
1
Fork 0
Code Pull requests 5 Wiki Activity

fs: Split fcntl_rw_hint()

Browse source 
Split fcntl_rw_hint() such that there is one helper function per fcntl.
Use READ_ONCE() and WRITE_ONCE() to access the i_write_hint member
instead of protecting such accesses with the inode lock. READ_ONCE() is
not used in I/O path code that reads i_write_hint. Users who want
F_SET_RW_HINT to affect I/O need to make sure that F_SET_RW_HINT has
completed before I/O is submitted that should use the configured write
hint.

Cc: Christoph Hellwig <hch@lst.de>
Suggested-by: Christoph Hellwig <hch@lst.de>
Cc: Kanchan Joshi <joshi.k@samsung.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240202203926.2478590-4-bvanassche@acm.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Bart Van Assche 2024-02-02 12:39:22 -08:00 committed by Christian Brauner
parent e769779c0c
commit 1505ba06e5
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
1 changed files with 24 additions and 21 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

45
fs/fcntl.c
View file

@ -290,32 +290,33 @@ static bool rw_hint_valid(u64 hint)
}
}
static long fcntl_rw_hint(struct file *file, unsigned int cmd,
unsigned long arg)
static long fcntl_get_rw_hint(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct inode *inode = file_inode(file);
u64 __user *argp = (u64 __user *)arg;
u64 hint = READ_ONCE(inode->i_write_hint);
if (copy_to_user(argp, &hint, sizeof(*argp)))
return -EFAULT;
return 0;
}
static long fcntl_set_rw_hint(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct inode *inode = file_inode(file);
u64 __user *argp = (u64 __user *)arg;
u64 hint;
switch (cmd) {
case F_GET_RW_HINT:
hint = inode->i_write_hint;
if (copy_to_user(argp, &hint, sizeof(*argp)))
return -EFAULT;
return 0;
case F_SET_RW_HINT:
if (copy_from_user(&hint, argp, sizeof(hint)))
return -EFAULT;
if (!rw_hint_valid(hint))
return -EINVAL;
inode_lock(inode);
inode->i_write_hint = hint;
inode_unlock(inode);
return 0;
default:
if (copy_from_user(&hint, argp, sizeof(hint)))
return -EFAULT;
if (!rw_hint_valid(hint))
return -EINVAL;
}
WRITE_ONCE(inode->i_write_hint, hint);
return 0;
}
static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
@ -421,8 +422,10 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
err = memfd_fcntl(filp, cmd, argi);
break;
case F_GET_RW_HINT:
err = fcntl_get_rw_hint(filp, cmd, arg);
break;
case F_SET_RW_HINT:
err = fcntl_rw_hint(filp, cmd, arg);
err = fcntl_set_rw_hint(filp, cmd, arg);
break;
default:
break;