From 29a8d9a0bce6a5abac1f313400c2e189e8d10e67 Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Tue, 6 Nov 2012 14:16:24 +0100 Subject: [PATCH] Btrfs: introduce GET_READ_MIRRORS functionality for btrfs_map_block() Before this commit, btrfs_map_block() was called with REQ_WRITE in order to retrieve the list of mirrors for a disk block. This needs to be changed for the device replace procedure since it makes a difference whether you are asking for read mirrors or for locations to write to. GET_READ_MIRRORS is introduced as a new interface to call btrfs_map_block(). In the current commit, the functionality is not yet changed, only the interface for GET_READ_MIRRORS is introduced and all the places that should use this new interface are adapted. The reason that REQ_WRITE cannot be abused anymore to retrieve a list of read mirrors is that during a running dev replace operation all write requests to the live filesystem are duplicated to also write to the target drive. Keep in mind that the target disk is only partially a valid copy of the source disk while the operation is ongoing. All writes go to the target disk, but not all reads would return valid data on the target disk. Therefore it is not possible anymore to abuse a REQ_WRITE interface to find valid mirrors for a REQ_READ. Signed-off-by: Stefan Behrens Signed-off-by: Chris Mason --- fs/btrfs/ctree.h | 3 +++ fs/btrfs/reada.c | 3 ++- fs/btrfs/scrub.c | 4 ++-- fs/btrfs/volumes.c | 8 ++++---- 4 files changed, 11 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 45e7f752b64..46bd7d5f504 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -174,6 +174,9 @@ static int btrfs_csum_sizes[] = { 4, 0 }; /* four bytes for CRC32 */ #define BTRFS_EMPTY_DIR_SIZE 0 +/* spefic to btrfs_map_block(), therefore not in include/linux/blk_types.h */ +#define REQ_GET_READ_MIRRORS (1 << 30) + #define BTRFS_FT_UNKNOWN 0 #define BTRFS_FT_REG_FILE 1 #define BTRFS_FT_DIR 2 diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index c705a48e676..96b93daa0bb 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -359,7 +359,8 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, * map block */ length = blocksize; - ret = btrfs_map_block(fs_info, REQ_WRITE, logical, &length, &bbio, 0); + ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length, + &bbio, 0); if (ret || !bbio || length < blocksize) goto error; diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index 30cbf6921c0..30ba9972489 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -1193,8 +1193,8 @@ static int scrub_setup_recheck_block(struct scrub_ctx *sctx, * with a length of PAGE_SIZE, each returned stripe * represents one mirror */ - ret = btrfs_map_block(fs_info, WRITE, logical, &mapped_length, - &bbio, 0); + ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, + &mapped_length, &bbio, 0); if (ret || !bbio || mapped_length < sublen) { kfree(bbio); return -EIO; diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index a4e0963bf45..de0c05cca39 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4103,7 +4103,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw, stripe_nr_end - stripe_nr_orig); stripe_index = do_div(stripe_nr, map->num_stripes); } else if (map->type & BTRFS_BLOCK_GROUP_RAID1) { - if (rw & (REQ_WRITE | REQ_DISCARD)) + if (rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)) num_stripes = map->num_stripes; else if (mirror_num) stripe_index = mirror_num - 1; @@ -4115,7 +4115,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw, } } else if (map->type & BTRFS_BLOCK_GROUP_DUP) { - if (rw & (REQ_WRITE | REQ_DISCARD)) { + if (rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)) { num_stripes = map->num_stripes; } else if (mirror_num) { stripe_index = mirror_num - 1; @@ -4129,7 +4129,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw, stripe_index = do_div(stripe_nr, factor); stripe_index *= map->sub_stripes; - if (rw & REQ_WRITE) + if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS)) num_stripes = map->sub_stripes; else if (rw & REQ_DISCARD) num_stripes = min_t(u64, map->sub_stripes * @@ -4242,7 +4242,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw, } } - if (rw & REQ_WRITE) { + if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS)) { if (map->type & (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10 | BTRFS_BLOCK_GROUP_DUP)) { -- 2.43.2