If implemented, get_fsid() can be used as a cheaper way of getting the f_fsid memeber of kstatfs, for callers that only care about fsid. fanotify is going to make use of that to get btrfs fsid from inode on every event. Suggested-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/20230920110429.f4wkfuls73pd55pv@quack3/ Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- Documentation/filesystems/locking.rst | 2 ++ Documentation/filesystems/vfs.rst | 4 ++++ fs/statfs.c | 14 ++++++++++++++ include/linux/fs.h | 1 + include/linux/statfs.h | 2 ++ 5 files changed, 23 insertions(+) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 7be2900806c8..a367950ee755 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -169,6 +169,7 @@ prototypes:: int (*freeze_fs) (struct super_block *); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); + int (*get_fsid) (struct inode *, __kernel_fsid_t *); int (*remount_fs) (struct super_block *, int *, char *); void (*umount_begin) (struct super_block *); int (*show_options)(struct seq_file *, struct dentry *); @@ -193,6 +194,7 @@ sync_fs: read freeze_fs: write unfreeze_fs: write statfs: maybe(read) (see below) +get_fsid: no remount_fs: write umount_begin: no show_options: no (namespace_sem) diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 99acc2e98673..f30f39f056ab 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -267,6 +267,7 @@ filesystem. The following members are defined: enum freeze_wholder who); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); + int (*get_fsid) (struct inode *, __kernel_fsid_t *); int (*remount_fs) (struct super_block *, int *, char *); void (*umount_begin) (struct super_block *); @@ -374,6 +375,9 @@ or bottom half). ``statfs`` called when the VFS needs to get filesystem statistics. +``get_fsid`` + called when the VFS needs to get only the f_fsid member of statfs. + ``remount_fs`` called when the filesystem is remounted. This is called with the kernel lock held diff --git a/fs/statfs.c b/fs/statfs.c index 96d1c3edf289..60a6af7356b7 100644 --- a/fs/statfs.c +++ b/fs/statfs.c @@ -69,11 +69,25 @@ static int statfs_by_dentry(struct dentry *dentry, struct kstatfs *buf) return retval; } +int inode_get_fsid(struct inode *inode, __kernel_fsid_t *fsid) +{ + if (!inode->i_sb->s_op->get_fsid) + return -EOPNOTSUPP; + + return inode->i_sb->s_op->get_fsid(inode, fsid); +} +EXPORT_SYMBOL(inode_get_fsid); + int vfs_get_fsid(struct dentry *dentry, __kernel_fsid_t *fsid) { struct kstatfs st; int error; + /* Avoid statfs if fs supports cheaper get_fsid() */ + error = inode_get_fsid(d_inode(dentry), fsid); + if (!error) + return 0; + error = statfs_by_dentry(dentry, &st); if (error) return error; diff --git a/include/linux/fs.h b/include/linux/fs.h index 4a40823c3c67..30d7d3347c49 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2008,6 +2008,7 @@ struct super_operations { int (*thaw_super) (struct super_block *, enum freeze_holder who); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); + int (*get_fsid)(struct inode *, __kernel_fsid_t *); int (*remount_fs) (struct super_block *, int *, char *); void (*umount_begin) (struct super_block *); diff --git a/include/linux/statfs.h b/include/linux/statfs.h index 02c862686ea3..c07f6d726e39 100644 --- a/include/linux/statfs.h +++ b/include/linux/statfs.h @@ -43,7 +43,9 @@ struct kstatfs { #define ST_RELATIME 0x1000 /* update atime relative to mtime/ctime */ #define ST_NOSYMFOLLOW 0x2000 /* do not follow symlinks */ +struct inode; struct dentry; +extern int inode_get_fsid(struct inode *inode, __kernel_fsid_t *fsid); extern int vfs_get_fsid(struct dentry *dentry, __kernel_fsid_t *fsid); static inline __kernel_fsid_t u64_to_fsid(u64 v) -- 2.34.1