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Subject[PATCH v3 46/68] cachefiles: Mark a backing file in use with an inode flag
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Use an inode flag, S_KERNEL_FILE, to mark that a backing file is in use by
the kernel to prevent cachefiles or other kernel services from interfering
with that file.

Using S_SWAPFILE instead isn't really viable as that has other effects in
the I/O paths.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819630256.215744.4815885535039369574.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163819642273.215744.6414248677118690672.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906931596.143852.8642051223094013028.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163906943215.143852.16972351425323967014.stgit@warthog.procyon.org.uk/ # v2
---

fs/cachefiles/internal.h | 2 ++
fs/cachefiles/namei.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 01071e7a7c02..7c67a70a3dff 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -187,6 +187,8 @@ extern struct kmem_cache *cachefiles_object_jar;
/*
* namei.c
*/
+extern void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
+ struct file *file);
extern struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
struct dentry *dir,
const char *name,
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 11a33209ab5f..db60a671c3fc 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -31,6 +31,18 @@ static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
return can_use;
}

+static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
+ struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ bool can_use;
+
+ inode_lock(inode);
+ can_use = __cachefiles_mark_inode_in_use(object, dentry);
+ inode_unlock(inode);
+ return can_use;
+}
+
/*
* Unmark a backing inode. The caller must hold the inode lock.
*/
@@ -43,6 +55,29 @@ static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
trace_cachefiles_mark_inactive(object, inode);
}

+/*
+ * Unmark a backing inode and tell cachefilesd that there's something that can
+ * be culled.
+ */
+void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
+ struct file *file)
+{
+ struct cachefiles_cache *cache = object->volume->cache;
+ struct inode *inode = file_inode(file);
+
+ if (inode) {
+ inode_lock(inode);
+ __cachefiles_unmark_inode_in_use(object, file->f_path.dentry);
+ inode_unlock(inode);
+
+ if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
+ atomic_long_add(inode->i_blocks, &cache->b_released);
+ if (atomic_inc_return(&cache->f_released))
+ cachefiles_state_changed(cache);
+ }
+ }
+}
+
/*
* get a subdirectory
*/

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