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721fb6fbfd
Detaching of mark connector from fsnotify_put_mark() can race with
unmounting of the filesystem like:
CPU1 CPU2
fsnotify_put_mark()
spin_lock(&conn->lock);
...
inode = fsnotify_detach_connector_from_object(conn)
spin_unlock(&conn->lock);
generic_shutdown_super()
fsnotify_unmount_inodes()
sees connector detached for inode
-> nothing to do
evict_inode()
barfs on pending inode reference
iput(inode);
Resulting in "Busy inodes after unmount" message and possible kernel
oops. Make fsnotify_unmount_inodes() properly wait for outstanding inode
references from detached connectors.
Note that the accounting of outstanding inode references in the
superblock can cause some cacheline contention on the counter. OTOH it
happens only during deletion of the last notification mark from an inode
(or during unlinking of watched inode) and that is not too bad. I have
measured time to create & delete inotify watch 100000 times from 64
processes in parallel (each process having its own inotify group and its
own file on a shared superblock) on a 64 CPU machine. Average and
standard deviation of 15 runs look like:
Avg Stddev
Vanilla 9.817400 0.276165
Fixed 9.710467 0.228294
So there's no statistically significant difference.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.