diff options
Diffstat (limited to 'include/linux/fs.h')
| -rw-r--r-- | include/linux/fs.h | 70 |
1 files changed, 61 insertions, 9 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index b70331f9f5b..365586a4c4d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1261,16 +1261,68 @@ struct super_operations { #endif }; -/* Inode state bits. Protected by inode_lock. */ -#define I_DIRTY_SYNC 1 /* Not dirty enough for O_DATASYNC */ -#define I_DIRTY_DATASYNC 2 /* Data-related inode changes pending */ -#define I_DIRTY_PAGES 4 /* Data-related inode changes pending */ -#define __I_LOCK 3 +/* + * Inode state bits. Protected by inode_lock. + * + * Three bits determine the dirty state of the inode, I_DIRTY_SYNC, + * I_DIRTY_DATASYNC and I_DIRTY_PAGES. + * + * Four bits define the lifetime of an inode. Initially, inodes are I_NEW, + * until that flag is cleared. I_WILL_FREE, I_FREEING and I_CLEAR are set at + * various stages of removing an inode. + * + * Two bits are used for locking and completion notification, I_LOCK and I_SYNC. + * + * I_DIRTY_SYNC Inode itself is dirty. + * I_DIRTY_DATASYNC Data-related inode changes pending + * I_DIRTY_PAGES Inode has dirty pages. Inode itself may be clean. + * I_NEW get_new_inode() sets i_state to I_LOCK|I_NEW. Both + * are cleared by unlock_new_inode(), called from iget(). + * I_WILL_FREE Must be set when calling write_inode_now() if i_count + * is zero. I_FREEING must be set when I_WILL_FREE is + * cleared. + * I_FREEING Set when inode is about to be freed but still has dirty + * pages or buffers attached or the inode itself is still + * dirty. + * I_CLEAR Set by clear_inode(). In this state the inode is clean + * and can be destroyed. + * + * Inodes that are I_WILL_FREE, I_FREEING or I_CLEAR are + * prohibited for many purposes. iget() must wait for + * the inode to be completely released, then create it + * anew. Other functions will just ignore such inodes, + * if appropriate. I_LOCK is used for waiting. + * + * I_LOCK Serves as both a mutex and completion notification. + * New inodes set I_LOCK. If two processes both create + * the same inode, one of them will release its inode and + * wait for I_LOCK to be released before returning. + * Inodes in I_WILL_FREE, I_FREEING or I_CLEAR state can + * also cause waiting on I_LOCK, without I_LOCK actually + * being set. find_inode() uses this to prevent returning + * nearly-dead inodes. + * I_SYNC Similar to I_LOCK, but limited in scope to writeback + * of inode dirty data. Having a seperate lock for this + * purpose reduces latency and prevents some filesystem- + * specific deadlocks. + * + * Q: Why does I_DIRTY_DATASYNC exist? It appears as if it could be replaced + * by (I_DIRTY_SYNC|I_DIRTY_PAGES). + * Q: What is the difference between I_WILL_FREE and I_FREEING? + * Q: igrab() only checks on (I_FREEING|I_WILL_FREE). Should it also check on + * I_CLEAR? If not, why? + */ +#define I_DIRTY_SYNC 1 +#define I_DIRTY_DATASYNC 2 +#define I_DIRTY_PAGES 4 +#define I_NEW 8 +#define I_WILL_FREE 16 +#define I_FREEING 32 +#define I_CLEAR 64 +#define __I_LOCK 7 #define I_LOCK (1 << __I_LOCK) -#define I_FREEING 16 -#define I_CLEAR 32 -#define I_NEW 64 -#define I_WILL_FREE 128 +#define __I_SYNC 8 +#define I_SYNC (1 << __I_SYNC) #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES) |