diff options
| -rw-r--r-- | fs/inode.c | 45 |
1 files changed, 38 insertions, 7 deletions
diff --git a/fs/inode.c b/fs/inode.c index 05ea293d5f32..46a3e120b196 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -717,6 +717,43 @@ repeat: return NULL; } +/* + * Each cpu owns a range of LAST_INO_BATCH numbers. + * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations, + * to renew the exhausted range. + * + * This does not significantly increase overflow rate because every CPU can + * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is + * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the + * 2^32 range, and is a worst-case. Even a 50% wastage would only increase + * overflow rate by 2x, which does not seem too significant. + * + * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW + * error if st_ino won't fit in target struct field. Use 32bit counter + * here to attempt to avoid that. + */ +#define LAST_INO_BATCH 1024 +static DEFINE_PER_CPU(unsigned int, last_ino); + +static unsigned int get_next_ino(void) +{ + unsigned int *p = &get_cpu_var(last_ino); + unsigned int res = *p; + +#ifdef CONFIG_SMP + if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) { + static atomic_t shared_last_ino; + int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino); + + res = next - LAST_INO_BATCH; + } +#endif + + *p = ++res; + put_cpu_var(last_ino); + return res; +} + /** * new_inode - obtain an inode * @sb: superblock @@ -731,12 +768,6 @@ repeat: */ struct inode *new_inode(struct super_block *sb) { - /* - * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW - * error if st_ino won't fit in target struct field. Use 32bit counter - * here to attempt to avoid that. - */ - static unsigned int last_ino; struct inode *inode; spin_lock_prefetch(&inode_lock); @@ -745,7 +776,7 @@ struct inode *new_inode(struct super_block *sb) if (inode) { spin_lock(&inode_lock); __inode_sb_list_add(inode); - inode->i_ino = ++last_ino; + inode->i_ino = get_next_ino(); inode->i_state = 0; spin_unlock(&inode_lock); } |