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@xxxxxxxxxx> cc: Amir Goldstein <amir73il@xxxxxxxxx> cc: Miklos Szeredi <miklos@xxxxxxxxxx> cc: linux-cachefs@xxxxxxxxxx cc: linux-unionfs@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/CAOQ4uxhRS3MGEnCUDcsB1RL0d1Oy0g0Rzm75hVFAJw2dJ7uKSA@xxxxxxxxxxxxxx/ [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, };
