diff options
author | James Bottomley <James.Bottomley@HansenPartnership.com> | 2009-06-12 10:02:03 -0500 |
---|---|---|
committer | James Bottomley <James.Bottomley@HansenPartnership.com> | 2009-06-12 10:02:03 -0500 |
commit | 82681a318f9f028ea64e61f24bbd9ac535531921 (patch) | |
tree | 529b6a5b4fd040fb54b7672b1a224ebd47445876 /fs/namespace.c | |
parent | 3860c97bd60a4525bb62eb90e3e7d2f02662ac59 (diff) | |
parent | 8ebf975608aaebd7feb33d77f07ba21a6380e086 (diff) |
[SCSI] Merge branch 'linus'
Conflicts:
drivers/message/fusion/mptsas.c
fixed up conflict between req->data_len accessors and mptsas driver updates.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r-- | fs/namespace.c | 327 |
1 files changed, 139 insertions, 188 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 134d494158d..2dd333b0fe7 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -131,10 +131,20 @@ struct vfsmount *alloc_vfsmnt(const char *name) INIT_LIST_HEAD(&mnt->mnt_share); INIT_LIST_HEAD(&mnt->mnt_slave_list); INIT_LIST_HEAD(&mnt->mnt_slave); - atomic_set(&mnt->__mnt_writers, 0); +#ifdef CONFIG_SMP + mnt->mnt_writers = alloc_percpu(int); + if (!mnt->mnt_writers) + goto out_free_devname; +#else + mnt->mnt_writers = 0; +#endif } return mnt; +#ifdef CONFIG_SMP +out_free_devname: + kfree(mnt->mnt_devname); +#endif out_free_id: mnt_free_id(mnt); out_free_cache: @@ -171,65 +181,38 @@ int __mnt_is_readonly(struct vfsmount *mnt) } EXPORT_SYMBOL_GPL(__mnt_is_readonly); -struct mnt_writer { - /* - * If holding multiple instances of this lock, they - * must be ordered by cpu number. - */ - spinlock_t lock; - struct lock_class_key lock_class; /* compiles out with !lockdep */ - unsigned long count; - struct vfsmount *mnt; -} ____cacheline_aligned_in_smp; -static DEFINE_PER_CPU(struct mnt_writer, mnt_writers); +static inline void inc_mnt_writers(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; +#else + mnt->mnt_writers++; +#endif +} -static int __init init_mnt_writers(void) +static inline void dec_mnt_writers(struct vfsmount *mnt) { - int cpu; - for_each_possible_cpu(cpu) { - struct mnt_writer *writer = &per_cpu(mnt_writers, cpu); - spin_lock_init(&writer->lock); - lockdep_set_class(&writer->lock, &writer->lock_class); - writer->count = 0; - } - return 0; +#ifdef CONFIG_SMP + (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; +#else + mnt->mnt_writers--; +#endif } -fs_initcall(init_mnt_writers); -static void unlock_mnt_writers(void) +static unsigned int count_mnt_writers(struct vfsmount *mnt) { +#ifdef CONFIG_SMP + unsigned int count = 0; int cpu; - struct mnt_writer *cpu_writer; for_each_possible_cpu(cpu) { - cpu_writer = &per_cpu(mnt_writers, cpu); - spin_unlock(&cpu_writer->lock); + count += *per_cpu_ptr(mnt->mnt_writers, cpu); } -} -static inline void __clear_mnt_count(struct mnt_writer *cpu_writer) -{ - if (!cpu_writer->mnt) - return; - /* - * This is in case anyone ever leaves an invalid, - * old ->mnt and a count of 0. - */ - if (!cpu_writer->count) - return; - atomic_add(cpu_writer->count, &cpu_writer->mnt->__mnt_writers); - cpu_writer->count = 0; -} - /* - * must hold cpu_writer->lock - */ -static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer, - struct vfsmount *mnt) -{ - if (cpu_writer->mnt == mnt) - return; - __clear_mnt_count(cpu_writer); - cpu_writer->mnt = mnt; + return count; +#else + return mnt->mnt_writers; +#endif } /* @@ -253,74 +236,73 @@ static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer, int mnt_want_write(struct vfsmount *mnt) { int ret = 0; - struct mnt_writer *cpu_writer; - cpu_writer = &get_cpu_var(mnt_writers); - spin_lock(&cpu_writer->lock); + preempt_disable(); + inc_mnt_writers(mnt); + /* + * The store to inc_mnt_writers must be visible before we pass + * MNT_WRITE_HOLD loop below, so that the slowpath can see our + * incremented count after it has set MNT_WRITE_HOLD. + */ + smp_mb(); + while (mnt->mnt_flags & MNT_WRITE_HOLD) + cpu_relax(); + /* + * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will + * be set to match its requirements. So we must not load that until + * MNT_WRITE_HOLD is cleared. + */ + smp_rmb(); if (__mnt_is_readonly(mnt)) { + dec_mnt_writers(mnt); ret = -EROFS; goto out; } - use_cpu_writer_for_mount(cpu_writer, mnt); - cpu_writer->count++; out: - spin_unlock(&cpu_writer->lock); - put_cpu_var(mnt_writers); + preempt_enable(); return ret; } EXPORT_SYMBOL_GPL(mnt_want_write); -static void lock_mnt_writers(void) -{ - int cpu; - struct mnt_writer *cpu_writer; - - for_each_possible_cpu(cpu) { - cpu_writer = &per_cpu(mnt_writers, cpu); - spin_lock(&cpu_writer->lock); - __clear_mnt_count(cpu_writer); - cpu_writer->mnt = NULL; - } +/** + * mnt_clone_write - get write access to a mount + * @mnt: the mount on which to take a write + * + * This is effectively like mnt_want_write, except + * it must only be used to take an extra write reference + * on a mountpoint that we already know has a write reference + * on it. This allows some optimisation. + * + * After finished, mnt_drop_write must be called as usual to + * drop the reference. + */ +int mnt_clone_write(struct vfsmount *mnt) +{ + /* superblock may be r/o */ + if (__mnt_is_readonly(mnt)) + return -EROFS; + preempt_disable(); + inc_mnt_writers(mnt); + preempt_enable(); + return 0; } +EXPORT_SYMBOL_GPL(mnt_clone_write); -/* - * These per-cpu write counts are not guaranteed to have - * matched increments and decrements on any given cpu. - * A file open()ed for write on one cpu and close()d on - * another cpu will imbalance this count. Make sure it - * does not get too far out of whack. +/** + * mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_want_write, but it takes a file and can + * do some optimisations if the file is open for write already */ -static void handle_write_count_underflow(struct vfsmount *mnt) +int mnt_want_write_file(struct file *file) { - if (atomic_read(&mnt->__mnt_writers) >= - MNT_WRITER_UNDERFLOW_LIMIT) - return; - /* - * It isn't necessary to hold all of the locks - * at the same time, but doing it this way makes - * us share a lot more code. - */ - lock_mnt_writers(); - /* - * vfsmount_lock is for mnt_flags. - */ - spin_lock(&vfsmount_lock); - /* - * If coalescing the per-cpu writer counts did not - * get us back to a positive writer count, we have - * a bug. - */ - if ((atomic_read(&mnt->__mnt_writers) < 0) && - !(mnt->mnt_flags & MNT_IMBALANCED_WRITE_COUNT)) { - WARN(1, KERN_DEBUG "leak detected on mount(%p) writers " - "count: %d\n", - mnt, atomic_read(&mnt->__mnt_writers)); - /* use the flag to keep the dmesg spam down */ - mnt->mnt_flags |= MNT_IMBALANCED_WRITE_COUNT; - } - spin_unlock(&vfsmount_lock); - unlock_mnt_writers(); + if (!(file->f_mode & FMODE_WRITE)) + return mnt_want_write(file->f_path.mnt); + else + return mnt_clone_write(file->f_path.mnt); } +EXPORT_SYMBOL_GPL(mnt_want_write_file); /** * mnt_drop_write - give up write access to a mount @@ -332,37 +314,9 @@ static void handle_write_count_underflow(struct vfsmount *mnt) */ void mnt_drop_write(struct vfsmount *mnt) { - int must_check_underflow = 0; - struct mnt_writer *cpu_writer; - - cpu_writer = &get_cpu_var(mnt_writers); - spin_lock(&cpu_writer->lock); - - use_cpu_writer_for_mount(cpu_writer, mnt); - if (cpu_writer->count > 0) { - cpu_writer->count--; - } else { - must_check_underflow = 1; - atomic_dec(&mnt->__mnt_writers); - } - - spin_unlock(&cpu_writer->lock); - /* - * Logically, we could call this each time, - * but the __mnt_writers cacheline tends to - * be cold, and makes this expensive. - */ - if (must_check_underflow) - handle_write_count_underflow(mnt); - /* - * This could be done right after the spinlock - * is taken because the spinlock keeps us on - * the cpu, and disables preemption. However, - * putting it here bounds the amount that - * __mnt_writers can underflow. Without it, - * we could theoretically wrap __mnt_writers. - */ - put_cpu_var(mnt_writers); + preempt_disable(); + dec_mnt_writers(mnt); + preempt_enable(); } EXPORT_SYMBOL_GPL(mnt_drop_write); @@ -370,24 +324,41 @@ static int mnt_make_readonly(struct vfsmount *mnt) { int ret = 0; - lock_mnt_writers(); + spin_lock(&vfsmount_lock); + mnt->mnt_flags |= MNT_WRITE_HOLD; /* - * With all the locks held, this value is stable + * After storing MNT_WRITE_HOLD, we'll read the counters. This store + * should be visible before we do. */ - if (atomic_read(&mnt->__mnt_writers) > 0) { - ret = -EBUSY; - goto out; - } + smp_mb(); + /* - * nobody can do a successful mnt_want_write() with all - * of the counts in MNT_DENIED_WRITE and the locks held. + * With writers on hold, if this value is zero, then there are + * definitely no active writers (although held writers may subsequently + * increment the count, they'll have to wait, and decrement it after + * seeing MNT_READONLY). + * + * It is OK to have counter incremented on one CPU and decremented on + * another: the sum will add up correctly. The danger would be when we + * sum up each counter, if we read a counter before it is incremented, + * but then read another CPU's count which it has been subsequently + * decremented from -- we would see more decrements than we should. + * MNT_WRITE_HOLD protects against this scenario, because + * mnt_want_write first increments count, then smp_mb, then spins on + * MNT_WRITE_HOLD, so it can't be decremented by another CPU while + * we're counting up here. */ - spin_lock(&vfsmount_lock); - if (!ret) + if (count_mnt_writers(mnt) > 0) + ret = -EBUSY; + else mnt->mnt_flags |= MNT_READONLY; + /* + * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers + * that become unheld will see MNT_READONLY. + */ + smp_wmb(); + mnt->mnt_flags &= ~MNT_WRITE_HOLD; spin_unlock(&vfsmount_lock); -out: - unlock_mnt_writers(); return ret; } @@ -410,6 +381,9 @@ void free_vfsmnt(struct vfsmount *mnt) { kfree(mnt->mnt_devname); mnt_free_id(mnt); +#ifdef CONFIG_SMP + free_percpu(mnt->mnt_writers); +#endif kmem_cache_free(mnt_cache, mnt); } @@ -442,11 +416,11 @@ struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, * lookup_mnt increments the ref count before returning * the vfsmount struct. */ -struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) +struct vfsmount *lookup_mnt(struct path *path) { struct vfsmount *child_mnt; spin_lock(&vfsmount_lock); - if ((child_mnt = __lookup_mnt(mnt, dentry, 1))) + if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) mntget(child_mnt); spin_unlock(&vfsmount_lock); return child_mnt; @@ -604,38 +578,18 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, static inline void __mntput(struct vfsmount *mnt) { - int cpu; struct super_block *sb = mnt->mnt_sb; /* - * We don't have to hold all of the locks at the - * same time here because we know that we're the - * last reference to mnt and that no new writers - * can come in. - */ - for_each_possible_cpu(cpu) { - struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu); - spin_lock(&cpu_writer->lock); - if (cpu_writer->mnt != mnt) { - spin_unlock(&cpu_writer->lock); - continue; - } - atomic_add(cpu_writer->count, &mnt->__mnt_writers); - cpu_writer->count = 0; - /* - * Might as well do this so that no one - * ever sees the pointer and expects - * it to be valid. - */ - cpu_writer->mnt = NULL; - spin_unlock(&cpu_writer->lock); - } - /* * This probably indicates that somebody messed * up a mnt_want/drop_write() pair. If this * happens, the filesystem was probably unable * to make r/w->r/o transitions. */ - WARN_ON(atomic_read(&mnt->__mnt_writers)); + /* + * atomic_dec_and_lock() used to deal with ->mnt_count decrements + * provides barriers, so count_mnt_writers() below is safe. AV + */ + WARN_ON(count_mnt_writers(mnt)); dput(mnt->mnt_root); free_vfsmnt(mnt); deactivate_super(sb); @@ -1106,11 +1060,8 @@ static int do_umount(struct vfsmount *mnt, int flags) * we just try to remount it readonly. */ down_write(&sb->s_umount); - if (!(sb->s_flags & MS_RDONLY)) { - lock_kernel(); + if (!(sb->s_flags & MS_RDONLY)) retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); - unlock_kernel(); - } up_write(&sb->s_umount); return retval; } @@ -1253,11 +1204,11 @@ Enomem: return NULL; } -struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry) +struct vfsmount *collect_mounts(struct path *path) { struct vfsmount *tree; down_write(&namespace_sem); - tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE); + tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); up_write(&namespace_sem); return tree; } @@ -1430,7 +1381,7 @@ static int graft_tree(struct vfsmount *mnt, struct path *path) goto out_unlock; err = -ENOENT; - if (IS_ROOT(path->dentry) || !d_unhashed(path->dentry)) + if (!d_unlinked(path->dentry)) err = attach_recursive_mnt(mnt, path, NULL); out_unlock: mutex_unlock(&path->dentry->d_inode->i_mutex); @@ -1601,7 +1552,7 @@ static int do_move_mount(struct path *path, char *old_name) down_write(&namespace_sem); while (d_mountpoint(path->dentry) && - follow_down(&path->mnt, &path->dentry)) + follow_down(path)) ; err = -EINVAL; if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) @@ -1612,7 +1563,7 @@ static int do_move_mount(struct path *path, char *old_name) if (IS_DEADDIR(path->dentry->d_inode)) goto out1; - if (!IS_ROOT(path->dentry) && d_unhashed(path->dentry)) + if (d_unlinked(path->dentry)) goto out1; err = -EINVAL; @@ -1676,7 +1627,9 @@ static int do_new_mount(struct path *path, char *type, int flags, if (!capable(CAP_SYS_ADMIN)) return -EPERM; + lock_kernel(); mnt = do_kern_mount(type, flags, name, data); + unlock_kernel(); if (IS_ERR(mnt)) return PTR_ERR(mnt); @@ -1695,10 +1648,10 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path, down_write(&namespace_sem); /* Something was mounted here while we slept */ while (d_mountpoint(path->dentry) && - follow_down(&path->mnt, &path->dentry)) + follow_down(path)) ; err = -EINVAL; - if (!check_mnt(path->mnt)) + if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) goto unlock; /* Refuse the same filesystem on the same mount point */ @@ -2092,10 +2045,8 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, if (retval < 0) goto out3; - lock_kernel(); retval = do_mount((char *)dev_page, dir_page, (char *)type_page, flags, (void *)data_page); - unlock_kernel(); free_page(data_page); out3: @@ -2175,9 +2126,9 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, error = -ENOENT; if (IS_DEADDIR(new.dentry->d_inode)) goto out2; - if (d_unhashed(new.dentry) && !IS_ROOT(new.dentry)) + if (d_unlinked(new.dentry)) goto out2; - if (d_unhashed(old.dentry) && !IS_ROOT(old.dentry)) + if (d_unlinked(old.dentry)) goto out2; error = -EBUSY; if (new.mnt == root.mnt || |