Commit 925d1c401fa6cfd0df5d2e37da8981494ccdec07 aka "procfs task exe symlink". introduced struct mm_struct::exe_file and struct mm_struct::num_exe_file_vmas.
The rationale is weak: unifying MMU and no-MMU version of /proc/*/exe code. For this a) struct mm_struct becomes bigger, b) mmap/munmap/exit become slower, c) patch adds more code than removes in fact. After commit 8feae13110d60cc6287afabc2887366b0eb226c2 aka "NOMMU: Make VMAs per MM as for MMU-mode linux" no-MMU kernels also maintain list of VMAs in ->mmap, so we can switch back for MMU version of /proc/*/exe. This also helps C/R, no need to save and restore ->exe_file and to count additional references. Signed-off-by: Alexey Dobriyan <[email protected]> --- fs/exec.c | 2 fs/proc/base.c | 105 +++++++++++++---------------------------------- include/linux/mm.h | 12 ----- include/linux/mm_types.h | 6 -- include/linux/proc_fs.h | 20 -------- kernel/fork.c | 3 - mm/mmap.c | 22 +-------- mm/nommu.c | 16 ------- 8 files changed, 36 insertions(+), 150 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -966,8 +966,6 @@ int flush_old_exec(struct linux_binprm * bprm) if (retval) goto out; - set_mm_exe_file(bprm->mm, bprm->file); - /* * Release all of the old mmap stuff */ --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -201,6 +201,36 @@ static int proc_root_link(struct inode *inode, struct path *path) return result; } +static int proc_exe_link(struct inode *inode, struct path *path) +{ + struct task_struct *tsk; + struct mm_struct *mm; + struct vm_area_struct *vma; + + tsk = get_proc_task(inode); + if (!tsk) + return -ENOENT; + mm = get_task_mm(tsk); + put_task_struct(tsk); + if (!mm) + return -ENOENT; + + down_read(&mm->mmap_sem); + for (vma = mm->mmap; vma; vma = vma->vm_next) { + if ((vma->vm_flags & VM_EXECUTABLE) && vma->vm_file) { + *path = vma->vm_file->f_path; + path_get(&vma->vm_file->f_path); + + up_read(&mm->mmap_sem); + mmput(mm); + return 0; + } + } + up_read(&mm->mmap_sem); + mmput(mm); + return -ENOENT; +} + /* * Return zero if current may access user memory in @task, -error if not. */ @@ -1248,81 +1278,6 @@ static const struct file_operations proc_pid_sched_operations = { #endif -/* - * We added or removed a vma mapping the executable. The vmas are only mapped - * during exec and are not mapped with the mmap system call. - * Callers must hold down_write() on the mm's mmap_sem for these - */ -void added_exe_file_vma(struct mm_struct *mm) -{ - mm->num_exe_file_vmas++; -} - -void removed_exe_file_vma(struct mm_struct *mm) -{ - mm->num_exe_file_vmas--; - if ((mm->num_exe_file_vmas == 0) && mm->exe_file){ - fput(mm->exe_file); - mm->exe_file = NULL; - } - -} - -void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) -{ - if (new_exe_file) - get_file(new_exe_file); - if (mm->exe_file) - fput(mm->exe_file); - mm->exe_file = new_exe_file; - mm->num_exe_file_vmas = 0; -} - -struct file *get_mm_exe_file(struct mm_struct *mm) -{ - struct file *exe_file; - - /* We need mmap_sem to protect against races with removal of - * VM_EXECUTABLE vmas */ - down_read(&mm->mmap_sem); - exe_file = mm->exe_file; - if (exe_file) - get_file(exe_file); - up_read(&mm->mmap_sem); - return exe_file; -} - -void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) -{ - /* It's safe to write the exe_file pointer without exe_file_lock because - * this is called during fork when the task is not yet in /proc */ - newmm->exe_file = get_mm_exe_file(oldmm); -} - -static int proc_exe_link(struct inode *inode, struct path *exe_path) -{ - struct task_struct *task; - struct mm_struct *mm; - struct file *exe_file; - - task = get_proc_task(inode); - if (!task) - return -ENOENT; - mm = get_task_mm(task); - put_task_struct(task); - if (!mm) - return -ENOENT; - exe_file = get_mm_exe_file(mm); - mmput(mm); - if (exe_file) { - *exe_path = exe_file->f_path; - path_get(&exe_file->f_path); - fput(exe_file); - return 0; - } else - return -ENOENT; -} - static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd) { struct inode *inode = dentry->d_inode; --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1121,18 +1121,6 @@ extern void exit_mmap(struct mm_struct *); extern int mm_take_all_locks(struct mm_struct *mm); extern void mm_drop_all_locks(struct mm_struct *mm); -#ifdef CONFIG_PROC_FS -/* From fs/proc/base.c. callers must _not_ hold the mm's exe_file_lock */ -extern void added_exe_file_vma(struct mm_struct *mm); -extern void removed_exe_file_vma(struct mm_struct *mm); -#else -static inline void added_exe_file_vma(struct mm_struct *mm) -{} - -static inline void removed_exe_file_vma(struct mm_struct *mm) -{} -#endif /* CONFIG_PROC_FS */ - extern int may_expand_vm(struct mm_struct *mm, unsigned long npages); extern int install_special_mapping(struct mm_struct *mm, unsigned long addr, unsigned long len, --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -269,12 +269,6 @@ struct mm_struct { */ struct task_struct *owner; #endif - -#ifdef CONFIG_PROC_FS - /* store ref to file /proc/<pid>/exe symlink points to */ - struct file *exe_file; - unsigned long num_exe_file_vmas; -#endif #ifdef CONFIG_MMU_NOTIFIER struct mmu_notifier_mm *mmu_notifier_mm; #endif --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -188,12 +188,6 @@ extern void proc_net_remove(struct net *net, const char *name); extern struct proc_dir_entry *proc_net_mkdir(struct net *net, const char *name, struct proc_dir_entry *parent); -/* While the {get|set|dup}_mm_exe_file functions are for mm_structs, they are - * only needed to implement /proc/<pid>|self/exe so we define them here. */ -extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file); -extern struct file *get_mm_exe_file(struct mm_struct *mm); -extern void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm); - #else #define proc_net_fops_create(net, name, mode, fops) ({ (void)(mode), NULL; }) @@ -240,20 +234,6 @@ static inline int pid_ns_prepare_proc(struct pid_namespace *ns) static inline void pid_ns_release_proc(struct pid_namespace *ns) { } - -static inline void set_mm_exe_file(struct mm_struct *mm, - struct file *new_exe_file) -{} - -static inline struct file *get_mm_exe_file(struct mm_struct *mm) -{ - return NULL; -} - -static inline void dup_mm_exe_file(struct mm_struct *oldmm, - struct mm_struct *newmm) -{} - #endif /* CONFIG_PROC_FS */ #if !defined(CONFIG_PROC_KCORE) --- a/kernel/fork.c +++ b/kernel/fork.c @@ -488,7 +488,6 @@ void mmput(struct mm_struct *mm) if (atomic_dec_and_test(&mm->mm_users)) { exit_aio(mm); exit_mmap(mm); - set_mm_exe_file(mm, NULL); if (!list_empty(&mm->mmlist)) { spin_lock(&mmlist_lock); list_del(&mm->mmlist); @@ -611,8 +610,6 @@ struct mm_struct *dup_mm(struct task_struct *tsk) if (init_new_context(tsk, mm)) goto fail_nocontext; - dup_mm_exe_file(oldmm, mm); - err = dup_mmap(mm, oldmm); if (err) goto free_pt; --- a/mm/mmap.c +++ b/mm/mmap.c @@ -236,11 +236,8 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) might_sleep(); if (vma->vm_ops && vma->vm_ops->close) vma->vm_ops->close(vma); - if (vma->vm_file) { + if (vma->vm_file) fput(vma->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - removed_exe_file_vma(vma->vm_mm); - } mpol_put(vma_policy(vma)); kmem_cache_free(vm_area_cachep, vma); return next; @@ -637,11 +634,8 @@ again: remove_next = 1 + (end > next->vm_end); spin_unlock(&mapping->i_mmap_lock); if (remove_next) { - if (file) { + if (file) fput(file); - if (next->vm_flags & VM_EXECUTABLE) - removed_exe_file_vma(mm); - } mm->map_count--; mpol_put(vma_policy(next)); kmem_cache_free(vm_area_cachep, next); @@ -1196,8 +1190,6 @@ munmap_back: error = file->f_op->mmap(file, vma); if (error) goto unmap_and_free_vma; - if (vm_flags & VM_EXECUTABLE) - added_exe_file_vma(mm); } else if (vm_flags & VM_SHARED) { error = shmem_zero_setup(vma); if (error) @@ -1853,11 +1845,8 @@ int split_vma(struct mm_struct * mm, struct vm_area_struct * vma, } vma_set_policy(new, pol); - if (new->vm_file) { + if (new->vm_file) get_file(new->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - added_exe_file_vma(mm); - } if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); @@ -2204,11 +2193,8 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, new_vma->vm_start = addr; new_vma->vm_end = addr + len; new_vma->vm_pgoff = pgoff; - if (new_vma->vm_file) { + if (new_vma->vm_file) get_file(new_vma->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - added_exe_file_vma(mm); - } if (new_vma->vm_ops && new_vma->vm_ops->open) new_vma->vm_ops->open(new_vma); vma_link(mm, new_vma, prev, rb_link, rb_parent); --- a/mm/nommu.c +++ b/mm/nommu.c @@ -719,11 +719,8 @@ static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma) kenter("%p", vma); if (vma->vm_ops && vma->vm_ops->close) vma->vm_ops->close(vma); - if (vma->vm_file) { + if (vma->vm_file) fput(vma->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - removed_exe_file_vma(mm); - } put_nommu_region(vma->vm_region); kmem_cache_free(vm_area_cachep, vma); } @@ -1216,10 +1213,6 @@ unsigned long do_mmap_pgoff(struct file *file, get_file(file); vma->vm_file = file; get_file(file); - if (vm_flags & VM_EXECUTABLE) { - added_exe_file_vma(current->mm); - vma->vm_mm = current->mm; - } } down_write(&nommu_region_sem); @@ -1357,11 +1350,8 @@ share: error_put_region: __put_nommu_region(region); if (vma) { - if (vma->vm_file) { + if (vma->vm_file) fput(vma->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - removed_exe_file_vma(vma->vm_mm); - } kmem_cache_free(vm_area_cachep, vma); } kleave(" = %d [pr]", ret); @@ -1373,8 +1363,6 @@ error: fput(region->vm_file); kmem_cache_free(vm_region_jar, region); fput(vma->vm_file); - if (vma->vm_flags & VM_EXECUTABLE) - removed_exe_file_vma(vma->vm_mm); kmem_cache_free(vm_area_cachep, vma); kleave(" = %d", ret); return ret; _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
