X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=kernel%2Ffs%2Fxfs%2Fxfs_extfree_item.h;h=8fa8651705e1dc33bb84f1234b411aca9c73ef76;hb=e09b41010ba33a20a87472ee821fa407a5b8da36;hp=0ffbce32d5693e05e042de8983c8274942616196;hpb=9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00;p=kvmfornfv.git

diff --git a/kernel/fs/xfs/xfs_extfree_item.h b/kernel/fs/xfs/xfs_extfree_item.h
index 0ffbce32d..8fa865170 100644
--- a/kernel/fs/xfs/xfs_extfree_item.h
+++ b/kernel/fs/xfs/xfs_extfree_item.h
@@ -39,9 +39,28 @@ struct kmem_zone;
  * "extent free done" log item described below.
  *
  * The EFI is reference counted so that it is not freed prior to both the EFI
- * and EFD being committed and unpinned. This ensures that when the last
- * reference goes away the EFI will always be in the AIL as it has been
- * unpinned, regardless of whether the EFD is processed before or after the EFI.
+ * and EFD being committed and unpinned. This ensures the EFI is inserted into
+ * the AIL even in the event of out of order EFI/EFD processing. In other words,
+ * an EFI is born with two references:
+ *
+ * 	1.) an EFI held reference to track EFI AIL insertion
+ * 	2.) an EFD held reference to track EFD commit
+ *
+ * On allocation, both references are the responsibility of the caller. Once the
+ * EFI is added to and dirtied in a transaction, ownership of reference one
+ * transfers to the transaction. The reference is dropped once the EFI is
+ * inserted to the AIL or in the event of failure along the way (e.g., commit
+ * failure, log I/O error, etc.). Note that the caller remains responsible for
+ * the EFD reference under all circumstances to this point. The caller has no
+ * means to detect failure once the transaction is committed, however.
+ * Therefore, an EFD is required after this point, even in the event of
+ * unrelated failure.
+ *
+ * Once an EFD is allocated and dirtied in a transaction, reference two
+ * transfers to the transaction. The EFD reference is dropped once it reaches
+ * the unpin handler. Similar to the EFI, the reference also drops in the event
+ * of commit failure or log I/O errors. Note that the EFD is not inserted in the
+ * AIL, so at this point both the EFI and EFD are freed.
  */
 typedef struct xfs_efi_log_item {
 	xfs_log_item_t		efi_item;
@@ -77,5 +96,6 @@ xfs_efd_log_item_t	*xfs_efd_init(struct xfs_mount *, xfs_efi_log_item_t *,
 int			xfs_efi_copy_format(xfs_log_iovec_t *buf,
 					    xfs_efi_log_format_t *dst_efi_fmt);
 void			xfs_efi_item_free(xfs_efi_log_item_t *);
+void			xfs_efi_release(struct xfs_efi_log_item *);
 
 #endif	/* __XFS_EXTFREE_ITEM_H__ */