| @@ -71,7 +71,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, · 70 unmodified lines |
| 71 | if (!(sc->gfp_mask & __GFP_FS)) | 71 | if (!(sc->gfp_mask & __GFP_FS)) |
| 72 | return SHRINK_STOP; | 72 | return SHRINK_STOP; |
| 73 | | 73 | |
| 74 | if (!grab_super_passive(sb)) | 74 | if (!trylock_super(sb)) |
| 75 | return SHRINK_STOP; | 75 | return SHRINK_STOP; |
| 76 | | 76 | |
| 77 | if (sb->s_op->nr_cached_objects) | 77 | if (sb->s_op->nr_cached_objects) |
| @@ -105,7 +105,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, · 27 unmodified lines |
| 105 | freed += sb->s_op->free_cached_objects(sb, sc); | 105 | freed += sb->s_op->free_cached_objects(sb, sc); |
| 106 | } | 106 | } |
| 107 | | 107 | |
| 108 | drop_super(sb); | 108 | up_read(&sb->s_umount); |
| 109 | return freed; | 109 | return freed; |
| 110 | } | 110 | } |
| 111 | | 111 | |
| @@ -118,7 +118,7 @@ static unsigned long super_cache_count(struct shrinker *shrink, · 6 unmodified lines |
| 118 | sb = container_of(shrink, struct super_block, s_shrink); | 118 | sb = container_of(shrink, struct super_block, s_shrink); |
| 119 | | 119 | |
| 120 | /* | 120 | /* |
| 121 | * Don't call grab_super_passive as it is a potential | 121 | * Don't call trylock_super as it is a potential |
| 122 | * scalability bottleneck. The counts could get updated | 122 | * scalability bottleneck. The counts could get updated |
| 123 | * between super_cache_count and super_cache_scan anyway. | 123 | * between super_cache_count and super_cache_scan anyway. |
| 124 | * Call to super_cache_count with shrinker_rwsem held | 124 | * Call to super_cache_count with shrinker_rwsem held |
| @@ -348,35 +348,31 @@ static int grab_super(struct super_block *s) __releases(sb_lock) · 223 unmodified lines |
| 348 | } | 348 | } |
| 349 | | 349 | |
| 350 | /* | 350 | /* |
| 351 | * grab_super_passive - acquire a passive reference | 351 | * trylock_super - try to grab ->s_umount shared |
| 352 | * @sb: reference we are trying to grab | 352 | * @sb: reference we are trying to grab |
| 353 | * | 353 | * |
| 354 | * Tries to acquire a passive reference. This is used in places where we | 354 | * Try to prevent fs shutdown. This is used in places where we |
| 355 | * cannot take an active reference but we need to ensure that the | 355 | * cannot take an active reference but we need to ensure that the |
| 356 | * superblock does not go away while we are working on it. It returns | 356 | * filesystem is not shut down while we are working on it. It returns |
| 357 | * false if a reference was not gained, and returns true with the s_umount | 357 | * false if we cannot acquire s_umount or if we lose the race and |
| 358 | * lock held in read mode if a reference is gained. On successful return, | 358 | * filesystem already got into shutdown, and returns true with the s_umount |
| 359 | * the caller must drop the s_umount lock and the passive reference when | 359 | * lock held in read mode in case of success. On successful return, |
| 360 | * done. | 360 | * the caller must drop the s_umount lock when done. |
| | 361 | * |
| | 362 | * Note that unlike get_super() et.al. this one does *not* bump ->s_count. |
| | 363 | * The reason why it's safe is that we are OK with doing trylock instead |
| | 364 | * of down_read(). There's a couple of places that are OK with that, but |
| | 365 | * it's very much not a general-purpose interface. |
| 361 | */ | 366 | */ |
| 362 | bool grab_super_passive(struct super_block *sb) | 367 | bool trylock_super(struct super_block *sb) |
| 363 | { | 368 | { |
| 364 | spin_lock(&sb_lock); | | |
| 365 | if (hlist_unhashed(&sb->s_instances)) { | | |
| 366 | spin_unlock(&sb_lock); | | |
| 367 | return false; | | |
| 368 | } | | |
| 369 | | | |
| 370 | sb->s_count++; | | |
| 371 | spin_unlock(&sb_lock); | | |
| 372 | | | |
| 373 | if (down_read_trylock(&sb->s_umount)) { | 369 | if (down_read_trylock(&sb->s_umount)) { |
| 374 | if (sb->s_root && (sb->s_flags & MS_BORN)) | 370 | if (!hlist_unhashed(&sb->s_instances) && |
| | 371 | sb->s_root && (sb->s_flags & MS_BORN)) |
| 375 | return true; | 372 | return true; |
| 376 | up_read(&sb->s_umount); | 373 | up_read(&sb->s_umount); |
| 377 | } | 374 | } |
| 378 | | 375 | |
| 379 | put_super(sb); | | |
| 380 | return false; | 376 | return false; |
| 381 | } | 377 | } |
| 382 | | 378 | |