Long time ago "/proc/self" was an honest symlink and all not-PID entries
were output before /proc/$PID. To not lose /proc/self in readdir output
after it became permanently positive dentry it was stuck before /proc/1.
One side effect of the change was that the code
d = opendir("/proc");
seekdir(d, 256);
stopped pointing to the first PID for applications that want to skip all
the crap.
Later "/proc/thread-self" was added in the same way.
It looks like ps and top aren't seeking over /proc but are simply
skipping over so nobody noticed.
Restore old behaviour, make seekdir(254) point to /proc/self and
seekdir(255) point to /proc/thread-self.
Commit in question:
commit 021ada7dff22d0d9540ff596cb0f8bb866755ee1
procfs: switch /proc/self away from proc_dir_entry
Signed-off-by: Alexey Dobriyan <[email protected]>
---
fs/proc/base.c | 14 ++++++--------
fs/proc/root.c | 4 ++--
2 files changed, 8 insertions(+), 10 deletions(-)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3230,8 +3230,6 @@ static struct tgid_iter next_tgid(struct pid_namespace
*ns, struct tgid_iter ite
return iter;
}
-#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)
-
/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file *file, struct dir_context *ctx)
{
@@ -3239,22 +3237,22 @@ int proc_pid_readdir(struct file *file, struct
dir_context *ctx)
struct pid_namespace *ns = file_inode(file)->i_sb->s_fs_info;
loff_t pos = ctx->pos;
- if (pos >= PID_MAX_LIMIT + TGID_OFFSET)
+ if (pos >= PID_MAX_LIMIT + FIRST_PROCESS_ENTRY)
return 0;
- if (pos == TGID_OFFSET - 2) {
+ if (pos == FIRST_PROCESS_ENTRY - 2) {
struct inode *inode = d_inode(ns->proc_self);
if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
- if (pos == TGID_OFFSET - 1) {
+ if (pos == FIRST_PROCESS_ENTRY - 1) {
struct inode *inode = d_inode(ns->proc_thread_self);
if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
- iter.tgid = pos - TGID_OFFSET;
+ iter.tgid = pos - FIRST_PROCESS_ENTRY;
iter.task = NULL;
for (iter = next_tgid(ns, iter);
iter.task;
@@ -3267,14 +3265,14 @@ int proc_pid_readdir(struct file *file, struct
dir_context *ctx)
continue;
len = snprintf(name, sizeof(name), "%u", iter.tgid);
- ctx->pos = iter.tgid + TGID_OFFSET;
+ ctx->pos = iter.tgid + FIRST_PROCESS_ENTRY;
if (!proc_fill_cache(file, ctx, name, len,
proc_pid_instantiate, iter.task, NULL)) {
put_task_struct(iter.task);
return 0;
}
}
- ctx->pos = PID_MAX_LIMIT + TGID_OFFSET;
+ ctx->pos = PID_MAX_LIMIT + FIRST_PROCESS_ENTRY;
return 0;
}
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -162,11 +162,11 @@ static struct dentry *proc_root_lookup(struct inode *
dir, struct dentry * dentr
static int proc_root_readdir(struct file *file, struct dir_context *ctx)
{
- if (ctx->pos < FIRST_PROCESS_ENTRY) {
+ if (ctx->pos < FIRST_PROCESS_ENTRY - 2) {
int error = proc_readdir(file, ctx);
if (unlikely(error <= 0))
return error;
- ctx->pos = FIRST_PROCESS_ENTRY;
+ ctx->pos = FIRST_PROCESS_ENTRY - 2;
}
return proc_pid_readdir(file, ctx);
