Overlayfs uses backing files with "fake" overlayfs f_path and "real" underlying f_inode, in order to use underlying inode aops for mapped files and to display the overlayfs path in /proc/<pid>/maps.
In preparation for storing the overlayfs "fake" path instead of the underlying "real" path in struct backing_file, define a noop helper file_user_path() that returns f_path for now. Use the new helper in procfs and kernel logs whenever a path of a mapped file is displayed to users. Signed-off-by: Amir Goldstein <[email protected]> --- arch/arc/kernel/troubleshoot.c | 3 ++- fs/proc/base.c | 2 +- fs/proc/nommu.c | 2 +- fs/proc/task_mmu.c | 4 ++-- fs/proc/task_nommu.c | 2 +- include/linux/fs.h | 14 ++++++++++++++ kernel/trace/trace_output.c | 2 +- 7 files changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c index d5b3ed2c58f5..097887e4a9b7 100644 --- a/arch/arc/kernel/troubleshoot.c +++ b/arch/arc/kernel/troubleshoot.c @@ -93,7 +93,8 @@ static void show_faulting_vma(unsigned long address) char *nm = "?"; if (vma->vm_file) { - nm = file_path(vma->vm_file, buf, ARC_PATH_MAX-1); + nm = d_path(file_user_path(vma->vm_file), buf, + ARC_PATH_MAX-1); if (IS_ERR(nm)) nm = "?"; } diff --git a/fs/proc/base.c b/fs/proc/base.c index ffd54617c354..20695c928ee6 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2218,7 +2218,7 @@ static int map_files_get_link(struct dentry *dentry, struct path *path) rc = -ENOENT; vma = find_exact_vma(mm, vm_start, vm_end); if (vma && vma->vm_file) { - *path = vma->vm_file->f_path; + *path = *file_user_path(vma->vm_file); path_get(path); rc = 0; } diff --git a/fs/proc/nommu.c b/fs/proc/nommu.c index 4d3493579458..c6e7ebc63756 100644 --- a/fs/proc/nommu.c +++ b/fs/proc/nommu.c @@ -58,7 +58,7 @@ static int nommu_region_show(struct seq_file *m, struct vm_region *region) if (file) { seq_pad(m, ' '); - seq_file_path(m, file, ""); + seq_path(m, file_user_path(file), ""); } seq_putc(m, '\n'); diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 3dd5be96691b..1593940ca01e 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -296,7 +296,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma) if (anon_name) seq_printf(m, "[anon_shmem:%s]", anon_name->name); else - seq_file_path(m, file, "\n"); + seq_path(m, file_user_path(file), "\n"); goto done; } @@ -1967,7 +1967,7 @@ static int show_numa_map(struct seq_file *m, void *v) if (file) { seq_puts(m, " file="); - seq_file_path(m, file, "\n\t= "); + seq_path(m, file_user_path(file), "\n\t= "); } else if (vma_is_initial_heap(vma)) { seq_puts(m, " heap"); } else if (vma_is_initial_stack(vma)) { diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index 7cebd397cc26..bce674533000 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -157,7 +157,7 @@ static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma) if (file) { seq_pad(m, ' '); - seq_file_path(m, file, ""); + seq_path(m, file_user_path(file), ""); } else if (mm && vma_is_initial_stack(vma)) { seq_pad(m, ' '); seq_puts(m, "[stack]"); diff --git a/include/linux/fs.h b/include/linux/fs.h index 7f7e7d2efbeb..a8e4e1cac48e 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2472,6 +2472,20 @@ static inline const struct path *file_real_path(struct file *f) return &f->f_path; } +/* + * file_user_path - get the path to display for memory mapped file + * + * When mmapping a file on a stackable filesystem (e.g., overlayfs), the file + * stored in ->vm_file is a backing file whose f_inode is on the underlying + * filesystem. When the mapped file path is displayed to user (e.g. via + * /proc/<pid>/maps), this helper should be used to get the path to display + * to the user, which is the path of the fd that user has requested to map. + */ +static inline const struct path *file_user_path(struct file *f) +{ + return &f->f_path; +} + static inline struct file *file_clone_open(struct file *file) { return dentry_open(&file->f_path, file->f_flags, file->f_cred); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index db575094c498..d8b302d01083 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -404,7 +404,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, vmstart = vma->vm_start; } if (file) { - ret = trace_seq_path(s, &file->f_path); + ret = trace_seq_path(s, file_user_path(file)); if (ret) trace_seq_printf(s, "[+0x%lx]", ip - vmstart); -- 2.34.1
