diff options
| author | Mateusz Guzik <mguzik@redhat.com> | 2017-10-03 12:58:15 +0200 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2017-11-05 18:58:07 -0500 |
| commit | c02b1a9b41c2e728289f96850580a3651e0a8b5f (patch) | |
| tree | 15497a5e1c48c022858bf4f050225dd70c8d894d | |
| parent | 5297908270549b734c7c2556745e2385b6d4941d (diff) | |
vfs: grab the lock instead of blocking in __fd_install during resizing
Explicit locking in the fallback case provides a safe state of the
table. Getting rid of blocking semantics makes __fd_install usable
again in non-sleepable contexts, which easies backporting efforts.
There is a side effect of slightly nicer assembly for the common case
as might_sleep can now be removed.
Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | Documentation/filesystems/porting | 4 | ||||
| -rw-r--r-- | fs/file.c | 11 |
2 files changed, 7 insertions, 8 deletions
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index 93e0a2404532..17bb4dc28fae 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -502,10 +502,6 @@ in your dentry operations instead. store it as cookie. -- [mandatory] - __fd_install() & fd_install() can now sleep. Callers should not - hold a spinlock or other resources that do not allow a schedule. --- -[mandatory] any symlink that might use page_follow_link_light/page_put_link() must have inode_nohighmem(inode) called before anything might start playing with its pagecache. No highmem pages should end up in the pagecache of such diff --git a/fs/file.c b/fs/file.c index 9d047bd046b0..4115503bb575 100644 --- a/fs/file.c +++ b/fs/file.c @@ -592,13 +592,16 @@ void __fd_install(struct files_struct *files, unsigned int fd, { struct fdtable *fdt; - might_sleep(); rcu_read_lock_sched(); - while (unlikely(files->resize_in_progress)) { + if (unlikely(files->resize_in_progress)) { rcu_read_unlock_sched(); - wait_event(files->resize_wait, !files->resize_in_progress); - rcu_read_lock_sched(); + spin_lock(&files->file_lock); + fdt = files_fdtable(files); + BUG_ON(fdt->fd[fd] != NULL); + rcu_assign_pointer(fdt->fd[fd], file); + spin_unlock(&files->file_lock); + return; } /* coupled with smp_wmb() in expand_fdtable() */ smp_rmb(); |