Commit 471d4011 authored by Suparna Bhattacharya's avatar Suparna Bhattacharya Committed by Linus Torvalds
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[PATCH] ext4: uninitialised extent handling 



Make it possible to add file preallocation support in future as an RO_COMPAT
feature by recognizing uninitialized extents as holes and limiting extent
length to keep the top bit of ee_len free for marking uninitialized extents.

Signed-off-by: default avatarSuparna Bhattacharya <suparna@in.ibm.com>
Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
Signed-off-by: default avatarDave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f65e6fba

fs/ext4/extents.c

+16 −0
Original line number Diff line number Diff line
@@ -1082,6 +1082,13 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, 
	    != le32_to_cpu(ex2->ee_block))

		return 0;



	/*

	 * To allow future support for preallocated extents to be added

	 * as an RO_COMPAT feature, refuse to merge to extents if

	 * can result in the top bit of ee_len being set

	 */

	if (le16_to_cpu(ex1->ee_len) + le16_to_cpu(ex2->ee_len) > EXT_MAX_LEN)

		return 0;

#ifdef AGRESSIVE_TEST

	if (le16_to_cpu(ex1->ee_len) >= 4)

		return 0;
@@ -1944,6 +1951,15 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, 
	        unsigned long ee_block = le32_to_cpu(ex->ee_block);

		ext4_fsblk_t ee_start = ext_pblock(ex);

		unsigned short ee_len  = le16_to_cpu(ex->ee_len);



		/*

		 * Allow future support for preallocated extents to be added

		 * as an RO_COMPAT feature:

		 * Uninitialized extents are treated as holes, except that

		 * we avoid (fail) allocating new blocks during a write.

		 */

		if (ee_len > EXT_MAX_LEN)

			goto out2;

		/* if found exent covers block, simple return it */

	        if (iblock >= ee_block && iblock < ee_block + ee_len) {

			newblock = iblock - ee_block + ee_start;

include/linux/ext4_fs_extents.h

+2 −0
Original line number Diff line number Diff line
@@ -141,6 +141,8 @@ typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *, 


#define EXT_MAX_BLOCK	0xffffffff



#define EXT_MAX_LEN	((1UL << 15) - 1)





#define EXT_FIRST_EXTENT(__hdr__) \

	((struct ext4_extent *) (((char *) (__hdr__)) +		\

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