diff options
| -rw-r--r-- | include/linux/fs.h | 15 | ||||
| -rw-r--r-- | include/linux/shmem_fs.h | 2 | ||||
| -rw-r--r-- | mm/shmem.c | 66 |
3 files changed, 78 insertions, 5 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 488c3ef93601..b1c3a14f12e8 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2946,6 +2946,21 @@ extern void discard_new_inode(struct inode *); extern unsigned int get_next_ino(void); extern void evict_inodes(struct super_block *sb); +/* + * Userspace may rely on the the inode number being non-zero. For example, glibc + * simply ignores files with zero i_ino in unlink() and other places. + * + * As an additional complication, if userspace was compiled with + * _FILE_OFFSET_BITS=32 on a 64-bit kernel we'll only end up reading out the + * lower 32 bits, so we need to check that those aren't zero explicitly. With + * _FILE_OFFSET_BITS=64, this may cause some harmless false-negatives, but + * better safe than sorry. + */ +static inline bool is_zero_ino(ino_t ino) +{ + return (u32)ino == 0; +} + extern void __iget(struct inode * inode); extern void iget_failed(struct inode *); extern void clear_inode(struct inode *); diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index 7a35a6901221..eb628696ec66 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -36,6 +36,8 @@ struct shmem_sb_info { unsigned char huge; /* Whether to try for hugepages */ kuid_t uid; /* Mount uid for root directory */ kgid_t gid; /* Mount gid for root directory */ + ino_t next_ino; /* The next per-sb inode number to use */ + ino_t __percpu *ino_batch; /* The next per-cpu inode number to use */ struct mempolicy *mpol; /* default memory policy for mappings */ spinlock_t shrinklist_lock; /* Protects shrinklist */ struct list_head shrinklist; /* List of shinkable inodes */ diff --git a/mm/shmem.c b/mm/shmem.c index b2abca3f7f33..585a82d87a92 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -260,18 +260,67 @@ bool vma_is_shmem(struct vm_area_struct *vma) static LIST_HEAD(shmem_swaplist); static DEFINE_MUTEX(shmem_swaplist_mutex); -static int shmem_reserve_inode(struct super_block *sb) +/* + * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and + * produces a novel ino for the newly allocated inode. + * + * It may also be called when making a hard link to permit the space needed by + * each dentry. However, in that case, no new inode number is needed since that + * internally draws from another pool of inode numbers (currently global + * get_next_ino()). This case is indicated by passing NULL as inop. + */ +#define SHMEM_INO_BATCH 1024 +static int shmem_reserve_inode(struct super_block *sb, ino_t *inop) { struct shmem_sb_info *sbinfo = SHMEM_SB(sb); - if (sbinfo->max_inodes) { + ino_t ino; + + if (!(sb->s_flags & SB_KERNMOUNT)) { spin_lock(&sbinfo->stat_lock); if (!sbinfo->free_inodes) { spin_unlock(&sbinfo->stat_lock); return -ENOSPC; } sbinfo->free_inodes--; + if (inop) { + ino = sbinfo->next_ino++; + if (unlikely(is_zero_ino(ino))) + ino = sbinfo->next_ino++; + if (unlikely(ino > UINT_MAX)) { + /* + * Emulate get_next_ino uint wraparound for + * compatibility + */ + ino = 1; + } + *inop = ino; + } spin_unlock(&sbinfo->stat_lock); + } else if (inop) { + /* + * __shmem_file_setup, one of our callers, is lock-free: it + * doesn't hold stat_lock in shmem_reserve_inode since + * max_inodes is always 0, and is called from potentially + * unknown contexts. As such, use a per-cpu batched allocator + * which doesn't require the per-sb stat_lock unless we are at + * the batch boundary. + */ + ino_t *next_ino; + next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu()); + ino = *next_ino; + if (unlikely(ino % SHMEM_INO_BATCH == 0)) { + spin_lock(&sbinfo->stat_lock); + ino = sbinfo->next_ino; + sbinfo->next_ino += SHMEM_INO_BATCH; + spin_unlock(&sbinfo->stat_lock); + if (unlikely(is_zero_ino(ino))) + ino++; + } + *inop = ino; + *next_ino = ++ino; + put_cpu(); } + return 0; } @@ -2222,13 +2271,14 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode struct inode *inode; struct shmem_inode_info *info; struct shmem_sb_info *sbinfo = SHMEM_SB(sb); + ino_t ino; - if (shmem_reserve_inode(sb)) + if (shmem_reserve_inode(sb, &ino)) return NULL; inode = new_inode(sb); if (inode) { - inode->i_ino = get_next_ino(); + inode->i_ino = ino; inode_init_owner(inode, dir, mode); inode->i_blocks = 0; inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); @@ -2932,7 +2982,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentr * first link must skip that, to get the accounting right. */ if (inode->i_nlink) { - ret = shmem_reserve_inode(inode->i_sb); + ret = shmem_reserve_inode(inode->i_sb, NULL); if (ret) goto out; } @@ -3584,6 +3634,7 @@ static void shmem_put_super(struct super_block *sb) { struct shmem_sb_info *sbinfo = SHMEM_SB(sb); + free_percpu(sbinfo->ino_batch); percpu_counter_destroy(&sbinfo->used_blocks); mpol_put(sbinfo->mpol); kfree(sbinfo); @@ -3626,6 +3677,11 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) #endif sbinfo->max_blocks = ctx->blocks; sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes; + if (sb->s_flags & SB_KERNMOUNT) { + sbinfo->ino_batch = alloc_percpu(ino_t); + if (!sbinfo->ino_batch) + goto failed; + } sbinfo->uid = ctx->uid; sbinfo->gid = ctx->gid; sbinfo->mode = ctx->mode; |