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Commit 77493f04 authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by Linus Torvalds
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procfs: fdinfo: extend information about epoll target files 

Since it is possbile to have same number in tfd field (say file added,
closed, then nother file dup'ed to same number and added back) it is
imposible to distinguish such target files solely by their numbers.

Strictly speaking regular applications don't need to recognize these
targets at all but for checkpoint/restore sake we need to collect
targets to be able to push them back on restore stage in a proper order.

Thus lets add file position, inode and device number where this target
lays.  This three fields can be used as a primary key for sorting, and
together with kcmp help CRIU can find out an exact file target (from the
whole set of processes being checkpointed).

Link: http://lkml.kernel.org/r/20170424154423.436491881@gmail.com


Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
Acked-by: default avatarAndrei Vagin <avagin@virtuozzo.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9263969a

Documentation/filesystems/proc.txt

+5 −1
Original line number Diff line number Diff line
@@ -1786,12 +1786,16 @@ pair provide additional information particular to the objects they represent. 
	pos:	0

	flags:	02

	mnt_id:	9

	tfd:        5 events:       1d data: ffffffffffffffff

	tfd:        5 events:       1d data: ffffffffffffffff pos:0 ino:61af sdev:7



	where 'tfd' is a target file descriptor number in decimal form,

	'events' is events mask being watched and the 'data' is data

	associated with a target [see epoll(7) for more details].



	The 'pos' is current offset of the target file in decimal form

	[see lseek(2)], 'ino' and 'sdev' are inode and device numbers

	where target file resides, all in hex format.



	Fsnotify files

	~~~~~~~~~~~~~~

	For inotify files the format is the following

fs/eventpoll.c

+6 −2
Original line number Diff line number Diff line
@@ -960,10 +960,14 @@ static void ep_show_fdinfo(struct seq_file *m, struct file *f) 
	mutex_lock(&ep->mtx);

	for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {

		struct epitem *epi = rb_entry(rbp, struct epitem, rbn);

		struct inode *inode = file_inode(epi->ffd.file);



		seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",

		seq_printf(m, "tfd: %8d events: %8x data: %16llx "

			   " pos:%lli ino:%lx sdev:%x\n",

			   epi->ffd.fd, epi->event.events,

			   (long long)epi->event.data);

			   (long long)epi->event.data,

			   (long long)epi->ffd.file->f_pos,

			   inode->i_ino, inode->i_sb->s_dev);

		if (seq_has_overflowed(m))

			break;

	}