| Message ID | 20200725051547.3718-1-kalou@tfz.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] This command attaches a description to a file descriptor for troubleshooting purposes. The free string is displayed in the process fdinfo file for that fd /proc/pid/fdinfo/fd. | expand |
Sorry about all the noise, please disregard this one. On Sat, Jul 25, 2020 at 7:04 PM Pascal Bouchareine <kalou@tfz.net> wrote: > > One intended usage is to allow processes to self-document sockets > for netstat and friends to report > > Signed-off-by: Pascal Bouchareine <kalou@tfz.net> > --- > Documentation/filesystems/proc.rst | 3 +++ > fs/fcntl.c | 19 +++++++++++++++++++ > fs/file_table.c | 2 ++ > fs/proc/fd.c | 5 +++++ > include/linux/fs.h | 3 +++ > include/uapi/linux/fcntl.h | 5 +++++ > 6 files changed, 37 insertions(+) > > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst > index 996f3cfe7030..ae8045650836 100644 > --- a/Documentation/filesystems/proc.rst > +++ b/Documentation/filesystems/proc.rst > @@ -1918,6 +1918,9 @@ A typical output is:: > flags: 0100002 > mnt_id: 19 > > +An optional 'desc' is set if the process documented its usage of > +the file via the fcntl command F_SET_DESCRIPTION. > + > All locks associated with a file descriptor are shown in its fdinfo too:: > > lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF > diff --git a/fs/fcntl.c b/fs/fcntl.c > index 2e4c0fa2074b..c1ef724a906e 100644 > --- a/fs/fcntl.c > +++ b/fs/fcntl.c > @@ -319,6 +319,22 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd, > } > } > > +static long fcntl_set_description(struct file *file, char __user *desc) > +{ > + char *d; > + > + d = strndup_user(desc, MAX_FILE_DESC_SIZE); > + if (IS_ERR(d)) > + return PTR_ERR(d); > + > + spin_lock(&file->f_lock); > + kfree(file->f_description); > + file->f_description = d; > + spin_unlock(&file->f_lock); > + > + return 0; > +} > + > static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, > struct file *filp) > { > @@ -426,6 +442,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, > case F_SET_FILE_RW_HINT: > err = fcntl_rw_hint(filp, cmd, arg); > break; > + case F_SET_DESCRIPTION: > + err = fcntl_set_description(filp, argp); > + break; > default: > break; > } > diff --git a/fs/file_table.c b/fs/file_table.c > index 656647f9575a..6673a48d2ea1 100644 > --- a/fs/file_table.c > +++ b/fs/file_table.c > @@ -272,6 +272,8 @@ static void __fput(struct file *file) > eventpoll_release(file); > locks_remove_file(file); > > + kfree(file->f_description); > + > ima_file_free(file); > if (unlikely(file->f_flags & FASYNC)) { > if (file->f_op->fasync) > diff --git a/fs/proc/fd.c b/fs/proc/fd.c > index 81882a13212d..60b3ff971b2b 100644 > --- a/fs/proc/fd.c > +++ b/fs/proc/fd.c > @@ -57,6 +57,11 @@ static int seq_show(struct seq_file *m, void *v) > (long long)file->f_pos, f_flags, > real_mount(file->f_path.mnt)->mnt_id); > > + spin_lock(&file->f_lock); > + if (file->f_description) > + seq_printf(m, "desc:\t%s\n", file->f_description); > + spin_unlock(&file->f_lock); > + > show_fd_locks(m, file, files); > if (seq_has_overflowed(m)) > goto out; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index f5abba86107d..09717bfa4e3b 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -980,6 +980,9 @@ struct file { > struct address_space *f_mapping; > errseq_t f_wb_err; > errseq_t f_sb_err; /* for syncfs */ > + > +#define MAX_FILE_DESC_SIZE 256 > + char *f_description; > } __randomize_layout > __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */ > > diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h > index 2f86b2ad6d7e..f86ff6dc45c7 100644 > --- a/include/uapi/linux/fcntl.h > +++ b/include/uapi/linux/fcntl.h > @@ -55,6 +55,11 @@ > #define F_GET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 13) > #define F_SET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 14) > > +/* > + * Set file description > + */ > +#define F_SET_DESCRIPTION (F_LINUX_SPECIFIC_BASE + 15) > + > /* > * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be > * used to clear any hints previously set. > -- > 2.25.1 >
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 996f3cfe7030..ae8045650836 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -1918,6 +1918,9 @@ A typical output is:: flags: 0100002 mnt_id: 19 +An optional 'desc' is set if the process documented its usage of +the file via the fcntl command F_SET_DESCRIPTION. + All locks associated with a file descriptor are shown in its fdinfo too:: lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF diff --git a/fs/fcntl.c b/fs/fcntl.c index 2e4c0fa2074b..c1ef724a906e 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -319,6 +319,22 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd, } } +static long fcntl_set_description(struct file *file, char __user *desc) +{ + char *d; + + d = strndup_user(desc, MAX_FILE_DESC_SIZE); + if (IS_ERR(d)) + return PTR_ERR(d); + + spin_lock(&file->f_lock); + kfree(file->f_description); + file->f_description = d; + spin_unlock(&file->f_lock); + + return 0; +} + static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, struct file *filp) { @@ -426,6 +442,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, case F_SET_FILE_RW_HINT: err = fcntl_rw_hint(filp, cmd, arg); break; + case F_SET_DESCRIPTION: + err = fcntl_set_description(filp, argp); + break; default: break; } diff --git a/fs/file_table.c b/fs/file_table.c index 656647f9575a..6673a48d2ea1 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -272,6 +272,8 @@ static void __fput(struct file *file) eventpoll_release(file); locks_remove_file(file); + kfree(file->f_description); + ima_file_free(file); if (unlikely(file->f_flags & FASYNC)) { if (file->f_op->fasync) diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 81882a13212d..60b3ff971b2b 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -57,6 +57,11 @@ static int seq_show(struct seq_file *m, void *v) (long long)file->f_pos, f_flags, real_mount(file->f_path.mnt)->mnt_id); + spin_lock(&file->f_lock); + if (file->f_description) + seq_printf(m, "desc:\t%s\n", file->f_description); + spin_unlock(&file->f_lock); + show_fd_locks(m, file, files); if (seq_has_overflowed(m)) goto out; diff --git a/include/linux/fs.h b/include/linux/fs.h index f5abba86107d..09717bfa4e3b 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -980,6 +980,9 @@ struct file { struct address_space *f_mapping; errseq_t f_wb_err; errseq_t f_sb_err; /* for syncfs */ + +#define MAX_FILE_DESC_SIZE 256 + char *f_description; } __randomize_layout __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */ diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 2f86b2ad6d7e..f86ff6dc45c7 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -55,6 +55,11 @@ #define F_GET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 13) #define F_SET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 14) +/* + * Set file description + */ +#define F_SET_DESCRIPTION (F_LINUX_SPECIFIC_BASE + 15) + /* * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be * used to clear any hints previously set.
One intended usage is to allow processes to self-document sockets for netstat and friends to report Signed-off-by: Pascal Bouchareine <kalou@tfz.net> --- Documentation/filesystems/proc.rst | 3 +++ fs/fcntl.c | 19 +++++++++++++++++++ fs/file_table.c | 2 ++ fs/proc/fd.c | 5 +++++ include/linux/fs.h | 3 +++ include/uapi/linux/fcntl.h | 5 +++++ 6 files changed, 37 insertions(+)