jbd2: add COW fields to struct jbd2_journal_handle (93737456) · Commits · 戴 / test

Add fields needed for the copy-on-write ext4 development work. The h_cowing flag is used by ext4 snapshots code to mark the task in COWING state. The h_XXX_credits fields are used to track buffer credits usage (accounted by COW and non-COW operations). The h_cow_XXX fields are used as per task debugging counters. Merging this commit into mainline will allow users to test ext4 snapshots as a standalone module, without the need to patch and install a development kernel. Signed-off-by:

Amir Goldstein <amir73il@users.sf.net> Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu>

include/linux/jbd2.h

+25 −3

Original line number	Diff line number	Diff line
		@@ -435,10 +435,32 @@ struct jbd2_journal_handle
		unsigned int h_sync:1; /* sync-on-close */
		unsigned int h_jdata:1; /* force data journaling */
		unsigned int h_aborted:1; /* fatal error on handle */
		unsigned int h_cowing:1; /* COWing block to snapshot */

		/* Number of buffers requested by user:
		* (before adding the COW credits factor) */
		unsigned int h_base_credits:14;

		/* Number of buffers the user is allowed to dirty:
		* (counts only buffers dirtied when !h_cowing) */
		unsigned int h_user_credits:14;


		#ifdef CONFIG_DEBUG_LOCK_ALLOC
		struct lockdep_map h_lockdep_map;
		#endif

		#ifdef CONFIG_JBD2_DEBUG
		/* COW debugging counters: */
		unsigned int h_cow_moved; /* blocks moved to snapshot */
		unsigned int h_cow_copied; /* blocks copied to snapshot */
		unsigned int h_cow_ok_jh; /* blocks already COWed during current
		transaction */
		unsigned int h_cow_ok_bitmap; /* blocks not set in COW bitmap */
		unsigned int h_cow_ok_mapped;/* blocks already mapped in snapshot */
		unsigned int h_cow_bitmaps; /* COW bitmaps created */
		unsigned int h_cow_excluded; /* blocks set in exclude bitmap */
		#endif
		};

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