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| author | Kees Cook <kees+treewide@kernel.org> | 2026-09-02 15:31:14 -0700 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2026-09-04 21:37:00 -0700 |
| commit | 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d (patch) | |
| tree | c65086f9bdcd48c6360fb7cb4598bca084da1f32 /Documentation/filesystems/dnotify.rst | |
| download | linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.tar.gz linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.zip | |
treewide: refresh kmalloc_obj() conversionsgrafted
This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci
This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.
Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.
Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
Diffstat (limited to 'Documentation/filesystems/dnotify.rst')
| -rw-r--r-- | Documentation/filesystems/dnotify.rst | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/Documentation/filesystems/dnotify.rst b/Documentation/filesystems/dnotify.rst new file mode 100644 index 000000000..a28a1f9ef --- /dev/null +++ b/Documentation/filesystems/dnotify.rst @@ -0,0 +1,75 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +Linux Directory Notification +============================ + + Stephen Rothwell <sfr@canb.auug.org.au> + +The intention of directory notification is to allow user applications +to be notified when a directory, or any of the files in it, are changed. +The basic mechanism involves the application registering for notification +on a directory using a fcntl(2) call and the notifications themselves +being delivered using signals. + +The application decides which "events" it wants to be notified about. +The currently defined events are: + + ========= ===================================================== + DN_ACCESS A file in the directory was accessed (read) + DN_MODIFY A file in the directory was modified (write,truncate) + DN_CREATE A file was created in the directory + DN_DELETE A file was unlinked from directory + DN_RENAME A file in the directory was renamed + DN_ATTRIB A file in the directory had its attributes + changed (chmod,chown) + ========= ===================================================== + +Usually, the application must reregister after each notification, but +if DN_MULTISHOT is or'ed with the event mask, then the registration will +remain until explicitly removed (by registering for no events). + +By default, SIGIO will be delivered to the process and no other useful +information. However, if the F_SETSIG fcntl(2) call is used to let the +kernel know which signal to deliver, a siginfo structure will be passed to +the signal handler and the si_fd member of that structure will contain the +file descriptor associated with the directory in which the event occurred. + +Preferably the application will choose one of the real time signals +(SIGRTMIN + <n>) so that the notifications may be queued. This is +especially important if DN_MULTISHOT is specified. Note that SIGRTMIN +is often blocked, so it is better to use (at least) SIGRTMIN + 1. + +Implementation expectations (features and bugs :-)) +--------------------------------------------------- + +The notification should work for any local access to files even if the +actual file system is on a remote server. This implies that remote +access to files served by local user mode servers should be notified. +Also, remote accesses to files served by a local kernel NFS server should +be notified. + +In order to make the impact on the file system code as small as possible, +the problem of hard links to files has been ignored. So if a file (x) +exists in two directories (a and b) then a change to the file using the +name "a/x" should be notified to a program expecting notifications on +directory "a", but will not be notified to one expecting notifications on +directory "b". + +Also, files that are unlinked, will still cause notifications in the +last directory that they were linked to. + +Configuration +------------- + +Dnotify is controlled via the CONFIG_DNOTIFY configuration option. When +disabled, fcntl(fd, F_NOTIFY, ...) will return -EINVAL. + +Example +------- +See tools/testing/selftests/filesystems/dnotify_test.c for an example. + +NOTE +---- +Beginning with Linux 2.6.13, dnotify has been replaced by inotify. +See Documentation/filesystems/inotify.rst for more information on it. |
