Commit 86aa1397 authored by Song Liu's avatar Song Liu Committed by Shaohua Li
Browse files

md/r5cache: read data into orig_page for prexor of cached data 



With write back cache, we use orig_page to do prexor. This patch
makes sure we read data into orig_page for it.

Flag R5_OrigPageUPTDODATE is added to show whether orig_page
has the latest data from raid disk.

We introduce a helper function uptodate_for_rmw() to simplify
the a couple conditions in handle_stripe_dirtying().

Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent d46d29f0

drivers/md/raid5-cache.c

+2 −0
Original line number Diff line number Diff line
@@ -2349,6 +2349,8 @@ void r5c_release_extra_page(struct stripe_head *sh) 
			struct page *p = sh->dev[i].orig_page;



			sh->dev[i].orig_page = sh->dev[i].page;

			clear_bit(R5_OrigPageUPTDODATE, &sh->dev[i].flags);



			if (!using_disk_info_extra_page)

				put_page(p);

		}

drivers/md/raid5.c

+35 −9
Original line number Diff line number Diff line
@@ -1015,6 +1015,16 @@ again: 


			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))

				WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));



			if (!op_is_write(op) &&

			    test_bit(R5_InJournal, &sh->dev[i].flags))

				/*

				 * issuing read for a page in journal, this

				 * must be preparing for prexor in rmw; read

				 * the data into orig_page

				 */

				sh->dev[i].vec.bv_page = sh->dev[i].orig_page;

			else

				sh->dev[i].vec.bv_page = sh->dev[i].page;

			bi->bi_vcnt = 1;

			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
@@ -2380,6 +2390,13 @@ static void raid5_end_read_request(struct bio * bi) 
		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))

			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);



		if (test_bit(R5_InJournal, &sh->dev[i].flags))

			/*

			 * end read for a page in journal, this

			 * must be preparing for prexor in rmw

			 */

			set_bit(R5_OrigPageUPTDODATE, &sh->dev[i].flags);



		if (atomic_read(&rdev->read_errors))

			atomic_set(&rdev->read_errors, 0);

	} else {
@@ -3594,6 +3611,21 @@ unhash: 
		break_stripe_batch_list(head_sh, STRIPE_EXPAND_SYNC_FLAGS);

}



/*

 * For RMW in write back cache, we need extra page in prexor to store the

 * old data. This page is stored in dev->orig_page.

 *

 * This function checks whether we have data for prexor. The exact logic

 * is:

 *       R5_UPTODATE && (!R5_InJournal || R5_OrigPageUPTDODATE)

 */

static inline bool uptodate_for_rmw(struct r5dev *dev)

{

	return (test_bit(R5_UPTODATE, &dev->flags)) &&

		(!test_bit(R5_InJournal, &dev->flags) ||

		 test_bit(R5_OrigPageUPTDODATE, &dev->flags));

}



static int handle_stripe_dirtying(struct r5conf *conf,

				  struct stripe_head *sh,

				  struct stripe_head_state *s,
@@ -3625,9 +3657,7 @@ static int handle_stripe_dirtying(struct r5conf *conf, 
		if ((dev->towrite || i == sh->pd_idx || i == sh->qd_idx ||

		     test_bit(R5_InJournal, &dev->flags)) &&

		    !test_bit(R5_LOCKED, &dev->flags) &&

		    !((test_bit(R5_UPTODATE, &dev->flags) &&

		       (!test_bit(R5_InJournal, &dev->flags) ||

			dev->page != dev->orig_page)) ||

		    !(uptodate_for_rmw(dev) ||

		      test_bit(R5_Wantcompute, &dev->flags))) {

			if (test_bit(R5_Insync, &dev->flags))

				rmw++;
@@ -3639,7 +3669,6 @@ static int handle_stripe_dirtying(struct r5conf *conf, 
		    i != sh->pd_idx && i != sh->qd_idx &&

		    !test_bit(R5_LOCKED, &dev->flags) &&

		    !(test_bit(R5_UPTODATE, &dev->flags) ||

		      test_bit(R5_InJournal, &dev->flags) ||

		      test_bit(R5_Wantcompute, &dev->flags))) {

			if (test_bit(R5_Insync, &dev->flags))

				rcw++;
@@ -3693,9 +3722,7 @@ static int handle_stripe_dirtying(struct r5conf *conf, 
			     i == sh->pd_idx || i == sh->qd_idx ||

			     test_bit(R5_InJournal, &dev->flags)) &&

			    !test_bit(R5_LOCKED, &dev->flags) &&

			    !((test_bit(R5_UPTODATE, &dev->flags) &&

			       (!test_bit(R5_InJournal, &dev->flags) ||

				dev->page != dev->orig_page)) ||

			    !(uptodate_for_rmw(dev) ||

			      test_bit(R5_Wantcompute, &dev->flags)) &&

			    test_bit(R5_Insync, &dev->flags)) {

				if (test_bit(STRIPE_PREREAD_ACTIVE,
@@ -3722,7 +3749,6 @@ static int handle_stripe_dirtying(struct r5conf *conf, 
			    i != sh->pd_idx && i != sh->qd_idx &&

			    !test_bit(R5_LOCKED, &dev->flags) &&

			    !(test_bit(R5_UPTODATE, &dev->flags) ||

			      test_bit(R5_InJournal, &dev->flags) ||

			      test_bit(R5_Wantcompute, &dev->flags))) {

				rcw++;

				if (test_bit(R5_Insync, &dev->flags) &&

drivers/md/raid5.h

+5 −0
Original line number Diff line number Diff line
@@ -322,6 +322,11 @@ enum r5dev_flags { 
			 * data and parity being written are in the journal

			 * device

			 */

	R5_OrigPageUPTDODATE,	/* with write back cache, we read old data into

				 * dev->orig_page for prexor. When this flag is

				 * set, orig_page contains latest data in the

				 * raid disk.

				 */

};



/*

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