Messages in this thread Patch in this message | | | Date | Tue, 24 Apr 2018 00:50:09 +0300 | From | Alexey Dobriyan <> | Subject | [PATCH] proc: restore seekdir("/proc", 256) semantics |
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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 <adobriyan@gmail.com> ---
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);
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