aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat
-rw-r--r--fs/inode.c1
-rw-r--r--fs/namei.c76
-rw-r--r--fs/stat.c4
-rw-r--r--include/linux/fs.h59
4 files changed, 106 insertions, 34 deletions
diff --git a/fs/inode.c b/fs/inode.c
index 5aab80dc008c..73920d555c88 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -143,6 +143,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
inode->i_op = &empty_iops;
inode->i_fop = &empty_fops;
inode->i_nlink = 1;
+ inode->i_opflags = 0;
inode->i_uid = 0;
inode->i_gid = 0;
atomic_set(&inode->i_writecount, 0);
diff --git a/fs/namei.c b/fs/namei.c
index 3d607bd80e09..4a98bf154d88 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -308,6 +308,26 @@ int generic_permission(struct inode *inode, int mask)
return -EACCES;
}
+/*
+ * We _really_ want to just do "generic_permission()" without
+ * even looking at the inode->i_op values. So we keep a cache
+ * flag in inode->i_opflags, that says "this has not special
+ * permission function, use the fast case".
+ */
+static inline int do_inode_permission(struct inode *inode, int mask)
+{
+ if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
+ if (likely(inode->i_op->permission))
+ return inode->i_op->permission(inode, mask);
+
+ /* This gets set once for the inode lifetime */
+ spin_lock(&inode->i_lock);
+ inode->i_opflags |= IOP_FASTPERM;
+ spin_unlock(&inode->i_lock);
+ }
+ return generic_permission(inode, mask);
+}
+
/**
* inode_permission - check for access rights to a given inode
* @inode: inode to check permission on
@@ -322,7 +342,7 @@ int inode_permission(struct inode *inode, int mask)
{
int retval;
- if (mask & MAY_WRITE) {
+ if (unlikely(mask & MAY_WRITE)) {
umode_t mode = inode->i_mode;
/*
@@ -339,11 +359,7 @@ int inode_permission(struct inode *inode, int mask)
return -EACCES;
}
- if (inode->i_op->permission)
- retval = inode->i_op->permission(inode, mask);
- else
- retval = generic_permission(inode, mask);
-
+ retval = do_inode_permission(inode, mask);
if (retval)
return retval;
@@ -1245,6 +1261,26 @@ static void terminate_walk(struct nameidata *nd)
}
}
+/*
+ * Do we need to follow links? We _really_ want to be able
+ * to do this check without having to look at inode->i_op,
+ * so we keep a cache of "no, this doesn't need follow_link"
+ * for the common case.
+ */
+static inline int do_follow_link(struct inode *inode, int follow)
+{
+ if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
+ if (likely(inode->i_op->follow_link))
+ return follow;
+
+ /* This gets set once for the inode lifetime */
+ spin_lock(&inode->i_lock);
+ inode->i_opflags |= IOP_NOFOLLOW;
+ spin_unlock(&inode->i_lock);
+ }
+ return 0;
+}
+
static inline int walk_component(struct nameidata *nd, struct path *path,
struct qstr *name, int type, int follow)
{
@@ -1267,7 +1303,7 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
terminate_walk(nd);
return -ENOENT;
}
- if (unlikely(inode->i_op->follow_link) && follow) {
+ if (do_follow_link(inode, follow)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
terminate_walk(nd);
@@ -1320,6 +1356,26 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
}
/*
+ * We really don't want to look at inode->i_op->lookup
+ * when we don't have to. So we keep a cache bit in
+ * the inode ->i_opflags field that says "yes, we can
+ * do lookup on this inode".
+ */
+static inline int can_lookup(struct inode *inode)
+{
+ if (likely(inode->i_opflags & IOP_LOOKUP))
+ return 1;
+ if (likely(!inode->i_op->lookup))
+ return 0;
+
+ /* We do this once for the lifetime of the inode */
+ spin_lock(&inode->i_lock);
+ inode->i_opflags |= IOP_LOOKUP;
+ spin_unlock(&inode->i_lock);
+ return 1;
+}
+
+/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
@@ -1398,10 +1454,10 @@ static int link_path_walk(const char *name, struct nameidata *nd)
if (err)
return err;
}
+ if (can_lookup(nd->inode))
+ continue;
err = -ENOTDIR;
- if (!nd->inode->i_op->lookup)
- break;
- continue;
+ break;
/* here ends the main loop */
last_component:
diff --git a/fs/stat.c b/fs/stat.c
index 961039121cb8..ba5316ffac61 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -27,12 +27,12 @@ void generic_fillattr(struct inode *inode, struct kstat *stat)
stat->uid = inode->i_uid;
stat->gid = inode->i_gid;
stat->rdev = inode->i_rdev;
+ stat->size = i_size_read(inode);
stat->atime = inode->i_atime;
stat->mtime = inode->i_mtime;
stat->ctime = inode->i_ctime;
- stat->size = i_size_read(inode);
- stat->blocks = inode->i_blocks;
stat->blksize = (1 << inode->i_blkbits);
+ stat->blocks = inode->i_blocks;
}
EXPORT_SYMBOL(generic_fillattr);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 786b3b1113cf..178cdb4f1d4a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -738,22 +738,54 @@ static inline int mapping_writably_mapped(struct address_space *mapping)
struct posix_acl;
#define ACL_NOT_CACHED ((void *)(-1))
+#define IOP_FASTPERM 0x0001
+#define IOP_LOOKUP 0x0002
+#define IOP_NOFOLLOW 0x0004
+
+/*
+ * Keep mostly read-only and often accessed (especially for
+ * the RCU path lookup and 'stat' data) fields at the beginning
+ * of the 'struct inode'
+ */
struct inode {
- /* RCU path lookup touches following: */
umode_t i_mode;
+ unsigned short i_opflags;
uid_t i_uid;
gid_t i_gid;
+ unsigned int i_flags;
+
+#ifdef CONFIG_FS_POSIX_ACL
+ struct posix_acl *i_acl;
+ struct posix_acl *i_default_acl;
+#endif
+
const struct inode_operations *i_op;
struct super_block *i_sb;
+ struct address_space *i_mapping;
- spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
- unsigned int i_flags;
- unsigned long i_state;
#ifdef CONFIG_SECURITY
void *i_security;
#endif
- struct mutex i_mutex;
+ /* Stat data, not accessed from path walking */
+ unsigned long i_ino;
+ unsigned int i_nlink;
+ dev_t i_rdev;
+ loff_t i_size;
+ struct timespec i_atime;
+ struct timespec i_mtime;
+ struct timespec i_ctime;
+ unsigned int i_blkbits;
+ blkcnt_t i_blocks;
+
+#ifdef __NEED_I_SIZE_ORDERED
+ seqcount_t i_size_seqcount;
+#endif
+
+ /* Misc */
+ unsigned long i_state;
+ spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
+ struct mutex i_mutex;
unsigned long dirtied_when; /* jiffies of first dirtying */
@@ -765,25 +797,12 @@ struct inode {
struct list_head i_dentry;
struct rcu_head i_rcu;
};
- unsigned long i_ino;
atomic_t i_count;
- unsigned int i_nlink;
- dev_t i_rdev;
- unsigned int i_blkbits;
u64 i_version;
- loff_t i_size;
-#ifdef __NEED_I_SIZE_ORDERED
- seqcount_t i_size_seqcount;
-#endif
- struct timespec i_atime;
- struct timespec i_mtime;
- struct timespec i_ctime;
- blkcnt_t i_blocks;
unsigned short i_bytes;
atomic_t i_dio_count;
const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
struct file_lock *i_flock;
- struct address_space *i_mapping;
struct address_space i_data;
#ifdef CONFIG_QUOTA
struct dquot *i_dquot[MAXQUOTAS];
@@ -806,10 +825,6 @@ struct inode {
atomic_t i_readcount; /* struct files open RO */
#endif
atomic_t i_writecount;
-#ifdef CONFIG_FS_POSIX_ACL
- struct posix_acl *i_acl;
- struct posix_acl *i_default_acl;
-#endif
void *i_private; /* fs or device private pointer */
};
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.