On Fri, 6 Mar 2015 09:41:00 -0500 "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > On Thu, Mar 05, 2015 at 06:37:18PM +0300, Andrey Vagin wrote: > > Let's show locks which are associated with a file descriptor in > > its fdinfo file. > > > > Currently we don't have a reliable way to determine who holds a lock. > > We can find some information in /proc/locks, but PID which is reported > > there can be wrong. For example, a process takes a lock, then forks a > > child and dies. In this case /proc/locks contains the parent pid, which > > can be reused by another process. > > > > $ cat /proc/locks > > ... > > 6: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF > > ... > > > > $ ps -C rpcbind > > PID TTY TIME CMD > > 332 ? 00:00:00 rpcbind > > > > $ cat /proc/332/fdinfo/4 > > pos: 0 > > flags: 0100000 > > mnt_id: 22 > > lock: 1: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF > > The major:minor part is redundant as long as you have the mnt_id, right? > > But I think it makes sense to leave it as you have it, with the same > format as /proc/locks. We get to share the kernel code, maybe userland > gets to reuse a little code too. > > And we should really remove that "ifdef WE_CAN_BREAK_LSLK_NOW" from > fs/locks.c, clearly that's not going to happen. (And add a comment that > the better solution may be to get the mntid from fdinfo, if that's > true?) > Yeah, I don't see a good reason to keep that in place either. It's been there since the git history started. I'll queue up a patch to remove it in v4.1. Thanks! > Anyway, that's a digression, ACK to the patch. > > --b. > > > > > $ ls -l /proc/332/fd/4 > > lr-x------ 1 root root 64 Mar 5 14:43 /proc/332/fd/4 -> /run/rpcbind.lock > > > > $ ls -l /proc/324/fd/ > > total 0 > > lrwx------ 1 root root 64 Feb 27 14:50 0 -> /dev/pts/0 > > lrwx------ 1 root root 64 Feb 27 14:50 1 -> /dev/pts/0 > > lrwx------ 1 root root 64 Feb 27 14:49 2 -> /dev/pts/0 > > > > You can see that the process with the 324 pid doesn't hold the lock. > > > > This information is required for proper dumping and restoring file > > locks. > > > > Cc: Jonathan Corbet <corbet@xxxxxxx> > > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx> > > Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > > Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > > Signed-off-by: Andrey Vagin <avagin@xxxxxxxxxx> > > --- > > Documentation/filesystems/proc.txt | 4 ++++ > > fs/locks.c | 38 ++++++++++++++++++++++++++++++++++++++ > > fs/proc/fd.c | 27 ++++++++++++++++++--------- > > include/linux/fs.h | 7 +++++++ > > 4 files changed, 67 insertions(+), 9 deletions(-) > > > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > > index a07ba61..6331623 100644 > > --- a/Documentation/filesystems/proc.txt > > +++ b/Documentation/filesystems/proc.txt > > @@ -1704,6 +1704,10 @@ A typical output is > > flags: 0100002 > > mnt_id: 19 > > > > +All locks associated with a file descriptor are shown in its fdinfo too. > > + > > +lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF > > + > > The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags > > pair provide additional information particular to the objects they represent. > > > > diff --git a/fs/locks.c b/fs/locks.c > > index 365c82e..815f832 100644 > > --- a/fs/locks.c > > +++ b/fs/locks.c > > @@ -2592,6 +2592,44 @@ static int locks_show(struct seq_file *f, void *v) > > return 0; > > } > > > > +static void __show_fd_locks(struct seq_file *f, > > + struct list_head *head, int *id, > > + struct file *filp, struct files_struct *files) > > +{ > > + struct file_lock *fl; > > + > > + list_for_each_entry(fl, head, fl_list) { > > + > > + if (filp != fl->fl_file) > > + continue; > > + if (fl->fl_owner != files && > > + fl->fl_owner != filp) > > + continue; > > + > > + (*id)++; > > + seq_puts(f, "lock:\t"); > > + lock_get_status(f, fl, *id, ""); > > + } > > +} > > + > > +void show_fd_locks(struct seq_file *f, > > + struct file *filp, struct files_struct *files) > > +{ > > + struct inode *inode = file_inode(filp); > > + struct file_lock_context *ctx; > > + int id = 0; > > + > > + ctx = inode->i_flctx; > > + if (!ctx) > > + return; > > + > > + spin_lock(&ctx->flc_lock); > > + __show_fd_locks(f, &ctx->flc_flock, &id, filp, files); > > + __show_fd_locks(f, &ctx->flc_posix, &id, filp, files); > > + __show_fd_locks(f, &ctx->flc_lease, &id, filp, files); > > + spin_unlock(&ctx->flc_lock); > > +} > > + > > static void *locks_start(struct seq_file *f, loff_t *pos) > > __acquires(&blocked_lock_lock) > > { > > diff --git a/fs/proc/fd.c b/fs/proc/fd.c > > index 8e5ad83..f04e13d 100644 > > --- a/fs/proc/fd.c > > +++ b/fs/proc/fd.c > > @@ -8,6 +8,7 @@ > > #include <linux/security.h> > > #include <linux/file.h> > > #include <linux/seq_file.h> > > +#include <linux/fs.h> > > > > #include <linux/proc_fs.h> > > > > @@ -48,16 +49,24 @@ static int seq_show(struct seq_file *m, void *v) > > put_files_struct(files); > > } > > > > - if (!ret) { > > - seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n", > > - (long long)file->f_pos, f_flags, > > - real_mount(file->f_path.mnt)->mnt_id); > > - if (file->f_op->show_fdinfo) > > - file->f_op->show_fdinfo(m, file); > > - ret = seq_has_overflowed(m); > > - fput(file); > > - } > > + if (ret) > > + return ret; > > + > > + seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n", > > + (long long)file->f_pos, f_flags, > > + real_mount(file->f_path.mnt)->mnt_id); > > + > > + show_fd_locks(m, file, files); > > + ret = seq_has_overflowed(m); > > + if (ret) > > + goto out; > > + > > + if (file->f_op->show_fdinfo) > > + file->f_op->show_fdinfo(m, file); > > + ret = seq_has_overflowed(m); > > > > +out: > > + fput(file); > > return ret; > > } > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index b4d71b5..ba0bd2a 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -1018,6 +1018,9 @@ extern void lease_get_mtime(struct inode *, struct timespec *time); > > extern int generic_setlease(struct file *, long, struct file_lock **, void **priv); > > extern int vfs_setlease(struct file *, long, struct file_lock **, void **); > > extern int lease_modify(struct file_lock *, int, struct list_head *); > > +struct files_struct; > > +extern void show_fd_locks(struct seq_file *f, > > + struct file *filp, struct files_struct *files); > > #else /* !CONFIG_FILE_LOCKING */ > > static inline int fcntl_getlk(struct file *file, unsigned int cmd, > > struct flock __user *user) > > @@ -1154,6 +1157,10 @@ static inline int lease_modify(struct file_lock *fl, int arg, > > { > > return -EINVAL; > > } > > + > > +struct files_struct; > > +static inline void show_fd_locks(struct seq_file *f, > > + struct file *filp, struct files_struct *files) {} > > #endif /* !CONFIG_FILE_LOCKING */ > > > > > > -- > > 2.1.0 -- Jeff Layton <jlayton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html