fanotify: Pre-allocate pool of error events

Pre-allocate slots for file system errors to have greater chances of
succeeding, since error events can happen in GFP_NOFS context.  This
patch introduces a group-wide mempool of error events, shared by all
FAN_FS_ERROR marks in this group.

Link: https://lore.kernel.org/r/20211025192746.66445-20-krisman@collabora.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 8f15244..01d68df 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -819,6 +819,9 @@ static void fanotify_free_group_priv(struct fsnotify_group *group)
        if (group->fanotify_data.ucounts)
                dec_ucount(group->fanotify_data.ucounts,
                           UCOUNT_FANOTIFY_GROUPS);
+
+       if (mempool_initialized(&group->fanotify_data.error_events_pool))
+               mempool_exit(&group->fanotify_data.error_events_pool);
 }
 
 static void fanotify_free_path_event(struct fanotify_event *event)

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index c42cf8f..a577e87 100644 (file)
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -141,6 +141,7 @@ enum fanotify_event_type {
        FANOTIFY_EVENT_TYPE_PATH,
        FANOTIFY_EVENT_TYPE_PATH_PERM,
        FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
+       FANOTIFY_EVENT_TYPE_FS_ERROR, /* struct fanotify_error_event */
        __FANOTIFY_EVENT_TYPE_NUM
 };
 
@@ -196,6 +197,16 @@ FANOTIFY_NE(struct fanotify_event *event)
        return container_of(event, struct fanotify_name_event, fae);
 }
 
+struct fanotify_error_event {
+       struct fanotify_event fae;
+};
+
+static inline struct fanotify_error_event *
+FANOTIFY_EE(struct fanotify_event *event)
+{
+       return container_of(event, struct fanotify_error_event, fae);
+}
+
 static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
 {
        if (event->type == FANOTIFY_EVENT_TYPE_FID)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 66ee3c2..2f4182b 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -30,6 +30,7 @@
 #define FANOTIFY_DEFAULT_MAX_EVENTS    16384
 #define FANOTIFY_OLD_DEFAULT_MAX_MARKS 8192
 #define FANOTIFY_DEFAULT_MAX_GROUPS    128
+#define FANOTIFY_DEFAULT_FEE_POOL_SIZE 32
 
 /*
  * Legacy fanotify marks limits (8192) is per group and we introduced a tunable
@@ -1054,6 +1055,15 @@ out_dec_ucounts:
        return ERR_PTR(ret);
 }
 
+static int fanotify_group_init_error_pool(struct fsnotify_group *group)
+{
+       if (mempool_initialized(&group->fanotify_data.error_events_pool))
+               return 0;
+
+       return mempool_init_kmalloc_pool(&group->fanotify_data.error_events_pool,
+                                        FANOTIFY_DEFAULT_FEE_POOL_SIZE,
+                                        sizeof(struct fanotify_error_event));
+}
 
 static int fanotify_add_mark(struct fsnotify_group *group,
                             fsnotify_connp_t *connp, unsigned int type,
@@ -1062,6 +1072,7 @@ static int fanotify_add_mark(struct fsnotify_group *group,
 {
        struct fsnotify_mark *fsn_mark;
        __u32 added;
+       int ret = 0;
 
        mutex_lock(&group->mark_mutex);
        fsn_mark = fsnotify_find_mark(connp, group);
@@ -1072,13 +1083,26 @@ static int fanotify_add_mark(struct fsnotify_group *group,
                        return PTR_ERR(fsn_mark);
                }
        }
+
+       /*
+        * Error events are pre-allocated per group, only if strictly
+        * needed (i.e. FAN_FS_ERROR was requested).
+        */
+       if (!(flags & FAN_MARK_IGNORED_MASK) && (mask & FAN_FS_ERROR)) {
+               ret = fanotify_group_init_error_pool(group);
+               if (ret)
+                       goto out;
+       }
+
        added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
        if (added & ~fsnotify_conn_mask(fsn_mark->connector))
                fsnotify_recalc_mask(fsn_mark->connector);
+
+out:
        mutex_unlock(&group->mark_mutex);
 
        fsnotify_put_mark(fsn_mark);
-       return 0;
+       return ret;
 }
 
 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 00dbaaf..51ef2b0 100644 (file)
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -19,6 +19,7 @@
 #include <linux/atomic.h>
 #include <linux/user_namespace.h>
 #include <linux/refcount.h>
+#include <linux/mempool.h>
 
 /*
  * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
@@ -246,6 +247,7 @@ struct fsnotify_group {
                        int flags;           /* flags from fanotify_init() */
                        int f_flags; /* event_f_flags from fanotify_init() */
                        struct ucounts *ucounts;
+                       mempool_t error_events_pool;
                } fanotify_data;
 #endif /* CONFIG_FANOTIFY */
        };