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Date: Mon, 31 Jan 2022 15:14:00 +0000
From: David Howells <dhowells@...hat.com>
To: Amir Goldstein <amir73il@...il.com>
Cc: Miklos Szeredi <miklos@...redi.hu>, linux-cachefs@...hat.com,
linux-unionfs@...r.kernel.org, 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 4/5] cachefiles: Use I_EXCL_INUSE instead of S_KERNEL_FILE
Get rid of S_KERNEL_FILE and use I_EXCL_INUSE instead, thereby sharing that
flag with overlayfs. This is used by cachefiles for two purposes: firstly,
to prevent simultaneous access to a backing file, which could cause data
corruption, and secondly, to allow cachefilesd to find out if it's allowed
to cull a backing file without having to have duplicate lookup
infrastructure (the VFS already has all the infrastructure that is
necessary to do the lookup; cachefiles just needs a single bit flag).
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Amir Goldstein <amir73il@...il.com>
cc: Miklos Szeredi <miklos@...redi.hu>
cc: linux-cachefs@...hat.com
cc: linux-unionfs@...r.kernel.org
Link: https://lore.kernel.org/r/CAOQ4uxhRS3MGEnCUDcsB1RL0d1Oy0g0Rzm75hVFAJw2dJ7uKSA@mail.gmail.com/ [1]
---
fs/cachefiles/namei.c | 46 ++++++++++++++++++++--------------------------
include/linux/fs.h | 2 +-
2 files changed, 21 insertions(+), 27 deletions(-)
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 8930c767d93a..0c88c82c188f 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -18,22 +18,19 @@ static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
- bool can_use = false;
+ bool locked;
- spin_lock(&inode->i_lock);
- if (!(inode->i_flags & S_KERNEL_FILE)) {
- inode->i_flags |= S_KERNEL_FILE;
+ locked = inode_excl_inuse_trylock(dentry, object ? object->debug_id : 0,
+ inode_excl_inuse_by_cachefiles);
+ if (locked) {
+ spin_lock(&inode->i_lock);
inode->i_state |= I_NO_REMOVE;
- trace_cachefiles_mark_active(object, inode);
- can_use = true;
+ spin_unlock(&inode->i_lock);
} else {
- trace_cachefiles_mark_failed(object, inode);
pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
dentry, inode->i_ino);
}
- spin_unlock(&inode->i_lock);
-
- return can_use;
+ return locked;
}
static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
@@ -57,10 +54,9 @@ static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
struct inode *inode = d_backing_inode(dentry);
spin_lock(&inode->i_lock);
- inode->i_flags &= ~S_KERNEL_FILE;
- inode->i_state &= ~I_NO_REMOVE;
+ inode->i_state |= I_NO_REMOVE;
spin_unlock(&inode->i_lock);
- trace_cachefiles_mark_inactive(object, inode);
+ inode_excl_inuse_unlock(dentry, object ? object->debug_id : 0);
}
/*
@@ -754,7 +750,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
goto lookup_error;
if (d_is_negative(victim))
goto lookup_put;
- if (d_inode(victim)->i_flags & S_KERNEL_FILE)
+ if (inode_is_excl_inuse(victim))
goto lookup_busy;
return victim;
@@ -790,6 +786,7 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
{
struct dentry *victim;
struct inode *inode;
+ bool locked;
int ret;
_enter(",%pd/,%s", dir, filename);
@@ -798,19 +795,16 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
if (IS_ERR(victim))
return PTR_ERR(victim);
- /* check to see if someone is using this object */
+ /* Check to see if someone is using this object and, if not, stop the
+ * cache from picking it back up.
+ */
inode = d_inode(victim);
inode_lock(inode);
- if (inode->i_flags & S_KERNEL_FILE) {
- ret = -EBUSY;
- } else {
- /* Stop the cache from picking it back up */
- inode->i_flags |= S_KERNEL_FILE;
- ret = 0;
- }
+ locked = inode_excl_inuse_trylock(victim, 0,
+ inode_excl_inuse_by_cachefiles);
inode_unlock(inode);
- if (ret < 0)
- goto error_unlock;
+ if (!locked)
+ goto busy;
ret = cachefiles_bury_object(cache, NULL, dir, victim,
FSCACHE_OBJECT_WAS_CULLED);
@@ -822,8 +816,8 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
_leave(" = 0");
return 0;
-error_unlock:
- inode_unlock(d_inode(dir));
+busy:
+ ret = -EBUSY;
error:
dput(victim);
if (ret == -ENOENT)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a273d5cde731..009ca9f783bd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2161,7 +2161,6 @@ struct super_operations {
#define S_ENCRYPTED (1 << 14) /* Encrypted file (using fs/crypto/) */
#define S_CASEFOLD (1 << 15) /* Casefolded file */
#define S_VERITY (1 << 16) /* Verity file (using fs/verity/) */
-#define S_KERNEL_FILE (1 << 17) /* File is in use by the kernel (eg. fs/cachefiles) */
/*
* Note that nosuid etc flags are inode-specific: setting some file-system
@@ -2394,6 +2393,7 @@ static inline bool inode_is_dirtytime_only(struct inode *inode)
}
enum inode_excl_inuse_by {
+ inode_excl_inuse_by_cachefiles,
inode_excl_inuse_by_overlayfs,
};
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