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locks: fix file locking on overlayfs

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This patch allows flock, posix locks, ofd locks and leases to work
correctly on overlayfs.

Instead of using the underlying inode for storing lock context use the
overlay inode.  This allows locks to be persistent across copy-up.

This is done by introducing locks_inode() helper and using it instead of
file_inode() to get the inode in locking code.  For non-overlayfs the two
are equivalent, except for an extra pointer dereference in locks_inode().

Since lock operations are in "struct file_operations" we must also make
sure not to call underlying filesystem's lock operations.  Introcude a
super block flag MS_NOREMOTELOCK to this effect.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
This commit is contained in:
Miklos Szeredi 2016-09-16 12:44:20 +02:00
parent f3fbbb0792
commit c568d68341
6 changed files with 46 additions and 27 deletions
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1
include/uapi/linux/fs.h
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@ -132,6 +132,7 @@ struct inodes_stat_t {
#define MS_LAZYTIME (1<<25) /* Update the on-disk [acm]times lazily */
/* These sb flags are internal to the kernel */
#define MS_NOREMOTELOCK (1<<27)
#define MS_NOSEC (1<<28)
#define MS_BORN (1<<29)
#define MS_ACTIVE (1<<30)