From 3418d036c81dcb604b7c7c71b209d5890a8418aa Mon Sep 17 00:00:00 2001 From: Artur Paszkiewicz Date: Thu, 9 Mar 2017 09:59:59 +0100 Subject: raid5-ppl: Partial Parity Log write logging implementation Implement the calculation of partial parity for a stripe and PPL write logging functionality. The description of PPL is added to the documentation. More details can be found in the comments in raid5-ppl.c. Attach a page for holding the partial parity data to stripe_head. Allocate it only if mddev has the MD_HAS_PPL flag set. Partial parity is the xor of not modified data chunks of a stripe and is calculated as follows: - reconstruct-write case: xor data from all not updated disks in a stripe - read-modify-write case: xor old data and parity from all updated disks in a stripe Implement it using the async_tx API and integrate into raid_run_ops(). It must be called when we still have access to old data, so do it when STRIPE_OP_BIODRAIN is set, but before ops_run_prexor5(). The result is stored into sh->ppl_page. Partial parity is not meaningful for full stripe write and is not stored in the log or used for recovery, so don't attempt to calculate it when stripe has STRIPE_FULL_WRITE. Put the PPL metadata structures to md_p.h because userspace tools (mdadm) will also need to read/write PPL. Warn about using PPL with enabled disk volatile write-back cache for now. It can be removed once disk cache flushing before writing PPL is implemented. Signed-off-by: Artur Paszkiewicz Signed-off-by: Shaohua Li --- include/uapi/linux/raid/md_p.h | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h index fe2112810c43..d9a1ead867b9 100644 --- a/include/uapi/linux/raid/md_p.h +++ b/include/uapi/linux/raid/md_p.h @@ -398,4 +398,31 @@ struct r5l_meta_block { #define R5LOG_VERSION 0x1 #define R5LOG_MAGIC 0x6433c509 + +struct ppl_header_entry { + __le64 data_sector; /* raid sector of the new data */ + __le32 pp_size; /* length of partial parity */ + __le32 data_size; /* length of data */ + __le32 parity_disk; /* member disk containing parity */ + __le32 checksum; /* checksum of partial parity data for this + * entry (~crc32c) */ +} __attribute__ ((__packed__)); + +#define PPL_HEADER_SIZE 4096 +#define PPL_HDR_RESERVED 512 +#define PPL_HDR_ENTRY_SPACE \ + (PPL_HEADER_SIZE - PPL_HDR_RESERVED - 4 * sizeof(u32) - sizeof(u64)) +#define PPL_HDR_MAX_ENTRIES \ + (PPL_HDR_ENTRY_SPACE / sizeof(struct ppl_header_entry)) + +struct ppl_header { + __u8 reserved[PPL_HDR_RESERVED];/* reserved space, fill with 0xff */ + __le32 signature; /* signature (family number of volume) */ + __le32 padding; /* zero pad */ + __le64 generation; /* generation number of the header */ + __le32 entries_count; /* number of entries in entry array */ + __le32 checksum; /* checksum of the header (~crc32c) */ + struct ppl_header_entry entries[PPL_HDR_MAX_ENTRIES]; +} __attribute__ ((__packed__)); + #endif -- cgit v1.2.3