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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: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2018-02-06 15:37:06 -08:00 committed by Linus Torvalds
parent 593bc695a1
commit 20d28cde55
1 changed files with 9 additions and 6 deletions
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15
fs/proc/base.c
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@ -2026,9 +2026,9 @@ out:
}
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))