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Subject[PATCH] 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.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/base.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2001,9 +2001,9 @@ 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 */
};

/*
@@ -2173,10 +2173,9 @@ 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();
}
@@ -2184,9 +2183,13 @@ 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))
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