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fs: convert mount flags to enum

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In prior kernel versions (5.8-6.8), commit 9f6c61f96f ("proc/mounts:
add cursor") introduced MNT_CURSOR, a flag used by readers from
/proc/mounts to keep their place while reading the file. Later, commit
2eea9ce431 ("mounts: keep list of mounts in an rbtree") removed this
flag and its value has since been repurposed.

For debuggers iterating over the list of mounts, cursors should be
skipped as they are irrelevant. Detecting whether an element is a cursor
can be difficult. Since the MNT_CURSOR flag is a preprocessor constant,
it's not present in debuginfo, and since its value is repurposed, we
cannot hard-code it. For this specific issue, cursors are possible to
detect in other ways, but ideally, we would be able to read the mount
flag definitions out of the debuginfo. For that reason, convert the
mount flags to an enum.

Link: https://github.com/osandov/drgn/pull/496
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Link: https://lore.kernel.org/20250507223402.2795029-1-stephen.s.brennan@oracle.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Stephen Brennan 2025-05-07 15:34:01 -07:00 committed by Christian Brauner
parent 7fc711739e
commit 101f2bbab5
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GPG key ID: 91C61BC06578DCA2
1 changed files with 40 additions and 37 deletions
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77
include/linux/mount.h
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@ -22,48 +22,51 @@ struct fs_context;
struct file;
struct path;
#define MNT_NOSUID 0x01
#define MNT_NODEV 0x02
#define MNT_NOEXEC 0x04
#define MNT_NOATIME 0x08
#define MNT_NODIRATIME 0x10
#define MNT_RELATIME 0x20
#define MNT_READONLY 0x40 /* does the user want this to be r/o? */
#define MNT_NOSYMFOLLOW 0x80
enum mount_flags {
MNT_NOSUID = 0x01,
MNT_NODEV = 0x02,
MNT_NOEXEC = 0x04,
MNT_NOATIME = 0x08,
MNT_NODIRATIME = 0x10,
MNT_RELATIME = 0x20,
MNT_READONLY = 0x40, /* does the user want this to be r/o? */
MNT_NOSYMFOLLOW = 0x80,
#define MNT_SHRINKABLE 0x100
#define MNT_WRITE_HOLD 0x200
MNT_SHRINKABLE = 0x100,
MNT_WRITE_HOLD = 0x200,
#define MNT_SHARED 0x1000 /* if the vfsmount is a shared mount */
#define MNT_UNBINDABLE 0x2000 /* if the vfsmount is a unbindable mount */
/*
* MNT_SHARED_MASK is the set of flags that should be cleared when a
* mount becomes shared. Currently, this is only the flag that says a
* mount cannot be bind mounted, since this is how we create a mount
* that shares events with another mount. If you add a new MNT_*
* flag, consider how it interacts with shared mounts.
*/
#define MNT_SHARED_MASK (MNT_UNBINDABLE)
#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
| MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
| MNT_READONLY | MNT_NOSYMFOLLOW)
#define MNT_ATIME_MASK (MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME )
MNT_SHARED = 0x1000, /* if the vfsmount is a shared mount */
MNT_UNBINDABLE = 0x2000, /* if the vfsmount is a unbindable mount */
#define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED)
MNT_INTERNAL = 0x4000,
#define MNT_INTERNAL 0x4000
MNT_LOCK_ATIME = 0x040000,
MNT_LOCK_NOEXEC = 0x080000,
MNT_LOCK_NOSUID = 0x100000,
MNT_LOCK_NODEV = 0x200000,
MNT_LOCK_READONLY = 0x400000,
MNT_LOCKED = 0x800000,
MNT_DOOMED = 0x1000000,
MNT_SYNC_UMOUNT = 0x2000000,
MNT_MARKED = 0x4000000,
MNT_UMOUNT = 0x8000000,
#define MNT_LOCK_ATIME 0x040000
#define MNT_LOCK_NOEXEC 0x080000
#define MNT_LOCK_NOSUID 0x100000
#define MNT_LOCK_NODEV 0x200000
#define MNT_LOCK_READONLY 0x400000
#define MNT_LOCKED 0x800000
#define MNT_DOOMED 0x1000000
#define MNT_SYNC_UMOUNT 0x2000000
#define MNT_MARKED 0x4000000
#define MNT_UMOUNT 0x8000000
/*
* MNT_SHARED_MASK is the set of flags that should be cleared when a
* mount becomes shared. Currently, this is only the flag that says a
* mount cannot be bind mounted, since this is how we create a mount
* that shares events with another mount. If you add a new MNT_*
* flag, consider how it interacts with shared mounts.
*/
MNT_SHARED_MASK = MNT_UNBINDABLE,
MNT_USER_SETTABLE_MASK = MNT_NOSUID | MNT_NODEV | MNT_NOEXEC
| MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME
| MNT_READONLY | MNT_NOSYMFOLLOW,
MNT_ATIME_MASK = MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME,
MNT_INTERNAL_FLAGS = MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL |
MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED,
};
struct vfsmount {
struct dentry *mnt_root; /* root of the mounted tree */