From b47e42d10e8c20525febccbd6e0dc8528861aea4 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Sat, 29 Mar 2025 09:42:18 +0100 Subject: [PATCH] super: use common iterator (Part 2) Use a common iterator for all callbacks. We could go for something even more elaborate (advance step-by-step similar to iov_iter) but I really don't think this is warranted. Link: https://lore.kernel.org/r/20250329-work-freeze-v2-5-a47af37ecc3d@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner --- fs/super.c | 48 +++++++++++++++++++++++++++++++++++++--------- include/linux/fs.h | 6 +----- 2 files changed, 40 insertions(+), 14 deletions(-) diff --git a/fs/super.c b/fs/super.c index 0dd208804a74..796e7f402a41 100644 --- a/fs/super.c +++ b/fs/super.c @@ -887,21 +887,46 @@ void drop_super_exclusive(struct super_block *sb) } EXPORT_SYMBOL(drop_super_exclusive); -void __iterate_supers(void (*f)(struct super_block *, void *), void *arg, bool excl) +enum super_iter_flags_t { + SUPER_ITER_EXCL = (1U << 0), + SUPER_ITER_UNLOCKED = (1U << 1), + SUPER_ITER_REVERSE = (1U << 2), +}; + +static inline struct super_block *first_super(enum super_iter_flags_t flags) +{ + if (flags & SUPER_ITER_REVERSE) + return list_last_entry(&super_blocks, struct super_block, s_list); + return list_first_entry(&super_blocks, struct super_block, s_list); +} + +static inline struct super_block *next_super(struct super_block *sb, + enum super_iter_flags_t flags) +{ + if (flags & SUPER_ITER_REVERSE) + return list_prev_entry(sb, s_list); + return list_next_entry(sb, s_list); +} + +static void __iterate_supers(void (*f)(struct super_block *, void *), void *arg, + enum super_iter_flags_t flags) { struct super_block *sb, *p = NULL; + bool excl = flags & SUPER_ITER_EXCL; - spin_lock(&sb_lock); - list_for_each_entry(sb, &super_blocks, s_list) { - bool locked; + guard(spinlock)(&sb_lock); + for (sb = first_super(flags); + !list_entry_is_head(sb, &super_blocks, s_list); + sb = next_super(sb, flags)) { if (super_flags(sb, SB_DYING)) continue; sb->s_count++; spin_unlock(&sb_lock); - locked = super_lock(sb, excl); - if (locked) { + if (flags & SUPER_ITER_UNLOCKED) { + f(sb, arg); + } else if (super_lock(sb, excl)) { f(sb, arg); super_unlock(sb, excl); } @@ -913,7 +938,11 @@ void __iterate_supers(void (*f)(struct super_block *, void *), void *arg, bool e } if (p) __put_super(p); - spin_unlock(&sb_lock); +} + +void iterate_supers(void (*f)(struct super_block *, void *), void *arg) +{ + __iterate_supers(f, arg, 0); } /** @@ -1097,7 +1126,8 @@ static void do_emergency_remount_callback(struct super_block *sb, void *unused) static void do_emergency_remount(struct work_struct *work) { - __iterate_supers(do_emergency_remount_callback, NULL, true); + __iterate_supers(do_emergency_remount_callback, NULL, + SUPER_ITER_EXCL | SUPER_ITER_REVERSE); kfree(work); printk("Emergency Remount complete\n"); } @@ -1124,7 +1154,7 @@ static void do_thaw_all_callback(struct super_block *sb, void *unused) static void do_thaw_all(struct work_struct *work) { - __iterate_supers(do_thaw_all_callback, NULL, true); + __iterate_supers(do_thaw_all_callback, NULL, SUPER_ITER_EXCL); kfree(work); printk(KERN_WARNING "Emergency Thaw complete\n"); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 5e007bffd00e..96f8c8a794ea 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3515,11 +3515,7 @@ extern void put_filesystem(struct file_system_type *fs); extern struct file_system_type *get_fs_type(const char *name); extern void drop_super(struct super_block *sb); extern void drop_super_exclusive(struct super_block *sb); -void __iterate_supers(void (*f)(struct super_block *, void *), void *arg, bool excl); -static inline void iterate_supers(void (*f)(struct super_block *, void *), void *arg) -{ - __iterate_supers(f, arg, false); -} +extern void iterate_supers(void (*f)(struct super_block *, void *), void *arg); extern void iterate_supers_type(struct file_system_type *, void (*)(struct super_block *, void *), void *); -- 2.25.1