Implement support for FS_IOC_GETFSLABEL and FS_IOC_SETFSLABEL ioctls for online reading and setting of file system label. ext4_ioctl_getlabel() is simple, just get the label from the primary superblock. This might not be the first sb on the file system if 'sb=' mount option is used. In ext4_ioctl_setlabel() we update what ext4 currently views as a primary superblock and then proceed to update backup superblocks. There are two caveats: - the primary superblock might not be the first superblock and so it might not be the one used by userspace tools if read directly off the disk. - because the primary superblock might not be the first superblock we potentialy have to update it as part of backup superblock update. However the first sb location is a bit more complicated than the rest so we have to account for that. The superblock modification is created generic enough so the infrastructure can be used for other potential superblock modification operations, such as chaning UUID. Tested with generic/492 with various configurations. I also checked the behavior with 'sb=' mount options, including very large file systems with and without sparse_super/sparse_super2.
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| @@ -2837,6 +2837,29 @@ TRACE_EVENT(ext4_fc_track_range, · 2836 unmodified lines | ||
| 2837 | 2837 | __entry->end) |
| 2838 | 2838 | ); |
| 2839 | 2839 | |
| 2840 | +TRACE_EVENT(ext4_update_sb, | |
| 2841 | + TP_PROTO(struct super_block *sb, ext4_fsblk_t fsblk, | |
| 2842 | + unsigned int flags), | |
| 2843 | + | |
| 2844 | + TP_ARGS(sb, fsblk, flags), | |
| 2845 | + | |
| 2846 | + TP_STRUCT__entry( | |
| 2847 | + __field(dev_t, dev) | |
| 2848 | + __field(ext4_fsblk_t, fsblk) | |
| 2849 | + __field(unsigned int, flags) | |
| 2850 | + ), | |
| 2851 | + | |
| 2852 | + TP_fast_assign( | |
| 2853 | + __entry->dev = sb->s_dev; | |
| 2854 | + __entry->fsblk = fsblk; | |
| 2855 | + __entry->flags = flags; | |
| 2856 | + ), | |
| 2857 | + | |
| 2858 | + TP_printk("dev %d,%d fsblk %llu flags %u", | |
| 2859 | + MAJOR(__entry->dev), MINOR(__entry->dev), | |
| 2860 | + __entry->fsblk, __entry->flags) | |
| 2861 | +); | |
| 2862 | + | |
| 2840 | 2863 | #endif /* _TRACE_EXT4_H */ |
| 2841 | 2864 | |
| 2842 | 2865 | /* This part must be outside protection */ |