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Commit ee20a983 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
Browse files

Btrfs: allow splitting of hole em's when dropping extent cache 



I noticed while running multi-threaded fsync tests that sometimes fsck would
complain about an improper gap.  This happens because we fail to add a hole
extent to the file, which was happening when we'd split a hole EM because
btrfs_drop_extent_cache was just discarding the whole em instead of splitting
it.  So this patch fixes this by allowing us to split a hole em properly, which
means that added holes actually get logged properly and we no longer see this
fsck error.  Thankfully we're tolerant of these sort of problems so a user would
not see any adverse effects of this bug, other than fsck complaining.  Thanks,

Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent ed8c4913

fs/btrfs/file.c

+40 −22
Original line number Diff line number Diff line
@@ -596,10 +596,11 @@ void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end, 
		if (no_splits)

			goto next;



		if (em->block_start < EXTENT_MAP_LAST_BYTE &&

		    em->start < start) {

		if (em->start < start) {

			split->start = em->start;

			split->len = start - em->start;



			if (em->block_start < EXTENT_MAP_LAST_BYTE) {

				split->orig_start = em->orig_start;

				split->block_start = em->block_start;
@@ -607,9 +608,17 @@ void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end, 
					split->block_len = em->block_len;

				else

					split->block_len = split->len;

			split->ram_bytes = em->ram_bytes;

				split->orig_block_len = max(split->block_len,

						em->orig_block_len);

				split->ram_bytes = em->ram_bytes;

			} else {

				split->orig_start = split->start;

				split->block_len = 0;

				split->block_start = em->block_start;

				split->orig_block_len = 0;

				split->ram_bytes = split->len;

			}



			split->generation = gen;

			split->bdev = em->bdev;

			split->flags = flags;
@@ -620,8 +629,7 @@ void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end, 
			split = split2;

			split2 = NULL;

		}

		if (em->block_start < EXTENT_MAP_LAST_BYTE &&

		    testend && em->start + em->len > start + len) {

		if (testend && em->start + em->len > start + len) {

			u64 diff = start + len - em->start;



			split->start = start + len;
@@ -630,19 +638,29 @@ void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end, 
			split->flags = flags;

			split->compress_type = em->compress_type;

			split->generation = gen;



			if (em->block_start < EXTENT_MAP_LAST_BYTE) {

				split->orig_block_len = max(em->block_len,

						    em->orig_block_len);

			split->ram_bytes = em->ram_bytes;



				split->ram_bytes = em->ram_bytes;

				if (compressed) {

					split->block_len = em->block_len;

					split->block_start = em->block_start;

					split->orig_start = em->orig_start;

				} else {

					split->block_len = split->len;

				split->block_start = em->block_start + diff;

					split->block_start = em->block_start

						+ diff;

					split->orig_start = em->orig_start;

				}

			} else {

				split->ram_bytes = split->len;

				split->orig_start = split->start;

				split->block_len = 0;

				split->block_start = em->block_start;

				split->orig_block_len = 0;

			}



			ret = add_extent_mapping(em_tree, split, modified);

			BUG_ON(ret); /* Logic error */