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Commit 20d28cde authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: less memory for /proc/*/map_files readdir 

dentry name can be evaluated later, right before calling into VFS.

Also, spend less time under ->mmap_sem.

Link: http://lkml.kernel.org/r/20171110163034.GA2534@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 593bc695

fs/proc/base.c

+9 −6
Original line number Diff line number Diff line
@@ -2026,9 +2026,9 @@ static int map_files_get_link(struct dentry *dentry, struct path *path) 
}



struct map_files_info {

	unsigned long	start;

	unsigned long	end;

	fmode_t		mode;

	unsigned int	len;

	unsigned char	name[4*sizeof(long)+2]; /* max: %lx-%lx\0 */

};



/*
@@ -2198,10 +2198,9 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx) 
			if (++pos <= ctx->pos)

				continue;



			info.start = vma->vm_start;

			info.end = vma->vm_end;

			info.mode = vma->vm_file->f_mode;

			info.len = snprintf(info.name,

					sizeof(info.name), "%lx-%lx",

					vma->vm_start, vma->vm_end);

			if (flex_array_put(fa, i++, &info, GFP_KERNEL))

				BUG();

		}
@@ -2209,9 +2208,13 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx) 
	up_read(&mm->mmap_sem);



	for (i = 0; i < nr_files; i++) {

		char buf[4 * sizeof(long) + 2];	/* max: %lx-%lx\0 */

		unsigned int len;



		p = flex_array_get(fa, i);

		len = snprintf(buf, sizeof(buf), "%lx-%lx", p->start, p->end);

		if (!proc_fill_cache(file, ctx,

				      p->name, p->len,

				      buf, len,

				      proc_map_files_instantiate,

				      task,

				      (void *)(unsigned long)p->mode))