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fanotify: implement "evictable" inode marks 

When an inode mark is created with flag FAN_MARK_EVICTABLE, it will not
pin the marked inode to inode cache, so when inode is evicted from cache
due to memory pressure, the mark will be lost.

When an inode mark with flag FAN_MARK_EVICATBLE is updated without using
this flag, the marked inode is pinned to inode cache.

When an inode mark is updated with flag FAN_MARK_EVICTABLE but an
existing mark already has the inode pinned, the mark update fails with
error EEXIST.

Evictable inode marks can be used to setup inode marks with ignored mask
to suppress events from uninteresting files or directories in a lazy
manner, upon receiving the first event, without having to iterate all
the uninteresting files or directories before hand.

The evictbale inode mark feature allows performing this lazy marks setup
without exhausting the system memory with pinned inodes.

This change does not enable the feature yet.

Link: https://lore.kernel.org/linux-fsdevel/CAOQ4uxiRDpuS=2uA6+ZUM7yG9vVU-u212tkunBmSnP_u=mkv=Q@mail.gmail.com/
Link: https://lore.kernel.org/r/20220422120327.3459282-15-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Amir Goldstein 2022-04-22 15:03:25 +03:00 committed by Jan Kara
parent 8998d11083
commit 7d5e005d98
3 changed files with 39 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/notify/fanotify/fanotify.h
View File

@ -497,6 +497,8 @@ static inline unsigned int fanotify_mark_user_flags(struct fsnotify_mark *mark)
if (mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
mflags |= FAN_MARK_IGNORED_SURV_MODIFY;
if (mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)
mflags |= FAN_MARK_EVICTABLE;
return mflags;
}

38
fs/notify/fanotify/fanotify_user.c
View File

@ -1084,6 +1084,7 @@ static int fanotify_remove_inode_mark(struct fsnotify_group *group,
static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
unsigned int fan_flags)
{
bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);
bool recalc = false;
/*
@ -1099,7 +1100,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
recalc = true;
}
return recalc;
if (fsn_mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE ||
want_iref == !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
return recalc;
/*
* NO_IREF may be removed from a mark, but not added.
* When removed, fsnotify_recalc_mask() will take the inode ref.
*/
WARN_ON_ONCE(!want_iref);
fsn_mark->flags &= ~FSNOTIFY_MARK_FLAG_NO_IREF;
return true;
}
static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
@ -1125,6 +1137,7 @@ static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
fsnotify_connp_t *connp,
unsigned int obj_type,
unsigned int fan_flags,
__kernel_fsid_t *fsid)
{
struct ucounts *ucounts = group->fanotify_data.ucounts;
@ -1147,6 +1160,9 @@ static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
}
fsnotify_init_mark(mark, group);
if (fan_flags & FAN_MARK_EVICTABLE)
mark->flags |= FSNOTIFY_MARK_FLAG_NO_IREF;
ret = fsnotify_add_mark_locked(mark, connp, obj_type, 0, fsid);
if (ret) {
fsnotify_put_mark(mark);
@ -1183,13 +1199,23 @@ static int fanotify_add_mark(struct fsnotify_group *group,
mutex_lock(&group->mark_mutex);
fsn_mark = fsnotify_find_mark(connp, group);
if (!fsn_mark) {
fsn_mark = fanotify_add_new_mark(group, connp, obj_type, fsid);
fsn_mark = fanotify_add_new_mark(group, connp, obj_type,
fan_flags, fsid);
if (IS_ERR(fsn_mark)) {
mutex_unlock(&group->mark_mutex);
return PTR_ERR(fsn_mark);
}
}
/*
* Non evictable mark cannot be downgraded to evictable mark.
*/
if (fan_flags & FAN_MARK_EVICTABLE &&
!(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)) {
ret = -EEXIST;
goto out;
}
/*
* Error events are pre-allocated per group, only if strictly
* needed (i.e. FAN_FS_ERROR was requested).
@ -1601,6 +1627,14 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
mark_type != FAN_MARK_FILESYSTEM)
goto fput_and_out;
/*
* Evictable is only relevant for inode marks, because only inode object
* can be evicted on memory pressure.
*/
if (flags & FAN_MARK_EVICTABLE &&
mark_type != FAN_MARK_INODE)
goto fput_and_out;
/*
* Events that do not carry enough information to report
* event->fd require a group that supports reporting fid. Those

1
include/uapi/linux/fanotify.h
View File

@ -82,6 +82,7 @@
#define FAN_MARK_IGNORED_SURV_MODIFY 0x00000040
#define FAN_MARK_FLUSH 0x00000080
/* FAN_MARK_FILESYSTEM is 0x00000100 */
#define FAN_MARK_EVICTABLE 0x00000200
/* These are NOT bitwise flags. Both bits can be used togther. */
#define FAN_MARK_INODE 0x00000000