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Message-ID: <164364197646.1476539.3635698398603811895.stgit@warthog.procyon.org.uk>
Date: Mon, 31 Jan 2022 15:12:56 +0000
From: David Howells <dhowells@...hat.com>
To: Amir Goldstein <amir73il@...il.com>
Cc: Miklos Szeredi <miklos@...redi.hu>, linux-unionfs@...r.kernel.org,
linux-cachefs@...hat.com, dhowells@...hat.com,
Christoph Hellwig <hch@...radead.org>,
Miklos Szeredi <miklos@...redi.hu>,
Jeff Layton <jlayton@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
torvalds@...ux-foundation.org, linux-unionfs@...r.kernel.org,
linux-cachefs@...hat.com, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] vfs, overlayfs,
cachefiles: Turn I_OVL_INUSE into something generic
Turn overlayfs's I_OVL_INUSE into something generic that cachefiles can
also use for excluding access to its own cache files by renaming it to
I_EXCL_INUSE as suggested by Amir[1] and hoisting the helpers to generic
code.
Suggested-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Amir Goldstein <amir73il@...il.com>
cc: Miklos Szeredi <miklos@...redi.hu>
cc: linux-unionfs@...r.kernel.org
cc: linux-cachefs@...hat.com
Link: https://lore.kernel.org/r/CAOQ4uxhRS3MGEnCUDcsB1RL0d1Oy0g0Rzm75hVFAJw2dJ7uKSA@mail.gmail.com/ [1]
---
fs/inode.c | 43 +++++++++++++++++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 3 ---
fs/overlayfs/super.c | 12 ++++++------
fs/overlayfs/util.c | 43 -------------------------------------------
include/linux/fs.h | 22 +++++++++++++++++++---
5 files changed, 68 insertions(+), 55 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 63324df6fa27..954719f66113 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2405,3 +2405,46 @@ struct timespec64 current_time(struct inode *inode)
return timestamp_truncate(now, inode);
}
EXPORT_SYMBOL(current_time);
+
+/**
+ * inode_excl_inuse_trylock - Try to exclusively lock an inode for kernel access
+ * @dentry: Reference to the inode to be locked
+ *
+ * Try to gain exclusive access to an inode for a kernel service, returning
+ * true if successful.
+ */
+bool inode_excl_inuse_trylock(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ bool locked = false;
+
+ spin_lock(&inode->i_lock);
+ if (!(inode->i_state & I_EXCL_INUSE)) {
+ inode->i_state |= I_EXCL_INUSE;
+ locked = true;
+ }
+ spin_unlock(&inode->i_lock);
+
+ return locked;
+}
+EXPORT_SYMBOL(inode_excl_inuse_trylock);
+
+/**
+ * inode_excl_inuse_unlock - Unlock exclusive kernel access to an inode
+ * @dentry: Reference to the inode to be unlocked
+ *
+ * Drop exclusive access to an inode for a kernel service. A warning is given
+ * if the inode was not marked for exclusive access.
+ */
+void inode_excl_inuse_unlock(struct dentry *dentry)
+{
+ if (dentry) {
+ struct inode *inode = d_inode(dentry);
+
+ spin_lock(&inode->i_lock);
+ WARN_ON(!(inode->i_state & I_EXCL_INUSE));
+ inode->i_state &= ~I_EXCL_INUSE;
+ spin_unlock(&inode->i_lock);
+ }
+}
+EXPORT_SYMBOL(inode_excl_inuse_unlock);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 2cd5741c873b..8415c0c6d40c 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -337,9 +337,6 @@ int ovl_check_setxattr(struct ovl_fs *ofs, struct dentry *upperdentry,
enum ovl_xattr ox, const void *value, size_t size,
int xerr);
int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry);
-bool ovl_inuse_trylock(struct dentry *dentry);
-void ovl_inuse_unlock(struct dentry *dentry);
-bool ovl_is_inuse(struct dentry *dentry);
bool ovl_need_index(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry);
void ovl_nlink_end(struct dentry *dentry);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7bb0a47cb615..5c3361a2dc7c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -224,10 +224,10 @@ static void ovl_free_fs(struct ovl_fs *ofs)
dput(ofs->indexdir);
dput(ofs->workdir);
if (ofs->workdir_locked)
- ovl_inuse_unlock(ofs->workbasedir);
+ inode_excl_inuse_unlock(ofs->workbasedir);
dput(ofs->workbasedir);
if (ofs->upperdir_locked)
- ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
+ inode_excl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
/* Hack! Reuse ofs->layers as a vfsmount array before freeing it */
mounts = (struct vfsmount **) ofs->layers;
@@ -1239,7 +1239,7 @@ static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
sb->s_flags |= SB_NOSEC;
- if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
+ if (inode_excl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
ofs->upperdir_locked = true;
} else {
err = ovl_report_in_use(ofs, "upperdir");
@@ -1499,7 +1499,7 @@ static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
ofs->workbasedir = dget(workpath.dentry);
- if (ovl_inuse_trylock(ofs->workbasedir)) {
+ if (inode_excl_inuse_trylock(ofs->workbasedir)) {
ofs->workdir_locked = true;
} else {
err = ovl_report_in_use(ofs, "workdir");
@@ -1722,7 +1722,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
if (err)
goto out;
- if (ovl_is_inuse(stack[i].dentry)) {
+ if (inode_is_excl_inuse(stack[i].dentry)) {
err = ovl_report_in_use(ofs, "lowerdir");
if (err) {
iput(trap);
@@ -1872,7 +1872,7 @@ static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
err = -ELOOP;
pr_err("overlapping %s path\n", name);
- } else if (ovl_is_inuse(parent)) {
+ } else if (inode_is_excl_inuse(parent)) {
err = ovl_report_in_use(ofs, name);
}
next = parent;
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index f48284a2a896..748c4b22deb3 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -724,49 +724,6 @@ int ovl_set_protattr(struct inode *inode, struct dentry *upper,
return 0;
}
-/**
- * Caller must hold a reference to inode to prevent it from being freed while
- * it is marked inuse.
- */
-bool ovl_inuse_trylock(struct dentry *dentry)
-{
- struct inode *inode = d_inode(dentry);
- bool locked = false;
-
- spin_lock(&inode->i_lock);
- if (!(inode->i_state & I_OVL_INUSE)) {
- inode->i_state |= I_OVL_INUSE;
- locked = true;
- }
- spin_unlock(&inode->i_lock);
-
- return locked;
-}
-
-void ovl_inuse_unlock(struct dentry *dentry)
-{
- if (dentry) {
- struct inode *inode = d_inode(dentry);
-
- spin_lock(&inode->i_lock);
- WARN_ON(!(inode->i_state & I_OVL_INUSE));
- inode->i_state &= ~I_OVL_INUSE;
- spin_unlock(&inode->i_lock);
- }
-}
-
-bool ovl_is_inuse(struct dentry *dentry)
-{
- struct inode *inode = d_inode(dentry);
- bool inuse;
-
- spin_lock(&inode->i_lock);
- inuse = (inode->i_state & I_OVL_INUSE);
- spin_unlock(&inode->i_lock);
-
- return inuse;
-}
-
/*
* Does this overlay dentry need to be indexed on copy up?
*/
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f3daaea16554..4c15e270f1ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2320,8 +2320,10 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
* wb stat updates to grab the i_pages lock. See
* inode_switch_wbs_work_fn() for details.
*
- * I_OVL_INUSE Used by overlayfs to get exclusive ownership on upper
- * and work dirs among overlayfs mounts.
+ * I_EXCL_INUSE Marked for exclusive use by a kernel service. Used by
+ * overlayfs to get exclusive ownership on upper and work
+ * dirs among overlayfs mounts and by cachefiles to prevent
+ * multiple access to a cache file.
*
* I_CREATING New object's inode in the middle of setting up.
*
@@ -2351,7 +2353,7 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
#define I_LINKABLE (1 << 10)
#define I_DIRTY_TIME (1 << 11)
#define I_WB_SWITCH (1 << 13)
-#define I_OVL_INUSE (1 << 14)
+#define I_EXCL_INUSE (1 << 14)
#define I_CREATING (1 << 15)
#define I_DONTCACHE (1 << 16)
#define I_SYNC_QUEUED (1 << 17)
@@ -2387,6 +2389,20 @@ static inline bool inode_is_dirtytime_only(struct inode *inode)
I_FREEING | I_WILL_FREE)) == I_DIRTY_TIME;
}
+bool inode_excl_inuse_trylock(struct dentry *dentry);
+void inode_excl_inuse_unlock(struct dentry *dentry);
+
+static inline bool inode_is_excl_inuse(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ bool inuse;
+
+ spin_lock(&inode->i_lock);
+ inuse = (inode->i_state & I_EXCL_INUSE);
+ spin_unlock(&inode->i_lock);
+ return inuse;
+}
+
extern void inc_nlink(struct inode *inode);
extern void drop_nlink(struct inode *inode);
extern void clear_nlink(struct inode *inode);
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