From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:37165 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750767Ab2KPFLP (ORCPT ); Fri, 16 Nov 2012 00:11:15 -0500 Message-ID: <50A5CC09.3050801@oracle.com> Date: Fri, 16 Nov 2012 13:15:53 +0800 From: Anand Jain MIME-Version: 1.0 To: Jan Schmidt CC: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: add label to snapshot and subvol References: <1351766770-4044-1-git-send-email-Anand.Jain@oracle.com> <1351766770-4044-4-git-send-email-Anand.Jain@oracle.com> <50976D36.5050904@jan-o-sch.net> In-Reply-To: <50976D36.5050904@jan-o-sch.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi Jan, Thanks for the review. Just posted the v2 patch for the btrfs kernel patch. Which, used the btrfs_root_item reserved space and used join_transaction -Anand On 05/11/12 15:39, Jan Schmidt wrote: > Hi Anand, > > Some comments on your kernel patch from a quick jump through: > > On 01.11.2012 11:46, Anand jain wrote: >> From: Anand Jain >> >> This modifies the struct btrfs_root_item to hold the label, >> and make it v3 of this structure. >> >> Signed-off-by: Anand Jain >> --- >> fs/btrfs/ctree.h | 14 ++++++++++++++ >> fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++++++++++ >> fs/btrfs/ioctl.h | 2 ++ >> fs/btrfs/root-tree.c | 44 +++++++++++++++++++++++--------------------- >> fs/btrfs/transaction.c | 1 + >> 5 files changed, 72 insertions(+), 21 deletions(-) >> >> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h >> index 994d255..b280256 100644 >> --- a/fs/btrfs/ctree.h >> +++ b/fs/btrfs/ctree.h >> @@ -759,6 +759,10 @@ struct btrfs_root_item { >> struct btrfs_timespec otime; >> struct btrfs_timespec stime; >> struct btrfs_timespec rtime; >> + >> + __le64 generation_v3; > > What is that supposed to be? > >> + char label[BTRFS_LABEL_SIZE]; /* Add label to subvol */ >> + >> __le64 reserved[8]; /* for future */ >> } __attribute__ ((__packed__)); > > You can't do that. There's a reason why we've got reserved bytes for > future use. Never change the struct's size. > >> @@ -2428,6 +2432,8 @@ BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct btrfs_root_item, >> last_snapshot, 64); >> BTRFS_SETGET_STACK_FUNCS(root_generation_v2, struct btrfs_root_item, >> generation_v2, 64); >> +BTRFS_SETGET_STACK_FUNCS(root_generation_v3, struct btrfs_root_item, >> + generation_v3, 64); >> BTRFS_SETGET_STACK_FUNCS(root_ctransid, struct btrfs_root_item, >> ctransid, 64); >> BTRFS_SETGET_STACK_FUNCS(root_otransid, struct btrfs_root_item, >> @@ -2441,6 +2447,14 @@ static inline bool btrfs_root_readonly(struct btrfs_root *root) >> { >> return (root->root_item.flags & cpu_to_le64(BTRFS_ROOT_SUBVOL_RDONLY)) != 0; >> } >> +static inline char * btrfs_root_label(struct btrfs_root *root) >> +{ >> + return (root->root_item.label); >> +} >> +static inline void btrfs_root_set_label(struct btrfs_root *root, char *val) >> +{ >> + memcpy(root->root_item.label,val,BTRFS_LABEL_SIZE); >> +} >> >> /* struct btrfs_root_backup */ >> BTRFS_SETGET_STACK_FUNCS(backup_tree_root, struct btrfs_root_backup, >> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c >> index e58bd9d..cce0128 100644 >> --- a/fs/btrfs/ioctl.c >> +++ b/fs/btrfs/ioctl.c >> @@ -3725,6 +3725,34 @@ static int btrfs_ioctl_set_label(struct btrfs_root *root, void __user *arg) >> return 0; >> } >> >> +static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root, >> + void __user *arg) >> +{ >> + char *label; >> + >> + label = btrfs_root_label(root); >> + if (copy_to_user(arg, label, BTRFS_LABEL_SIZE)) >> + return -EFAULT; >> + return 0; >> +} >> + >> +static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root, >> + void __user *arg) >> +{ >> + char label[BTRFS_LABEL_SIZE]; >> + struct btrfs_trans_handle *trans; >> + >> + if (copy_from_user(label, arg, BTRFS_LABEL_SIZE)) >> + return -EFAULT; >> + trans = btrfs_start_transaction(root, 1); >> + if (IS_ERR(trans)) >> + return PTR_ERR(trans); >> + btrfs_root_set_label(root, label); >> + btrfs_commit_transaction(trans, root); > > Why use start/commit instead of join/end here? > >> + return 0; >> +} >> + >> long btrfs_ioctl(struct file *file, unsigned int >> cmd, unsigned long arg) >> { >> @@ -3827,6 +3855,10 @@ long btrfs_ioctl(struct file *file, unsigned int >> return btrfs_ioctl_get_label(root, argp); >> case BTRFS_IOC_SET_LABEL: >> return btrfs_ioctl_set_label(root, argp); >> + case BTRFS_IOC_SUBVOL_GETLABEL: >> + return btrfs_ioctl_subvol_getlabel(root, argp); >> + case BTRFS_IOC_SUBVOL_SETLABEL: >> + return btrfs_ioctl_subvol_setlabel(root, argp); >> } >> >> return -ENOTTY; >> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h >> index 0c60fcb..1009a0c 100644 >> --- a/fs/btrfs/ioctl.h >> +++ b/fs/btrfs/ioctl.h >> @@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args { >> struct btrfs_ioctl_get_dev_stats) >> #define BTRFS_IOC_GET_LABEL _IOR(BTRFS_IOCTL_MAGIC, 53, __u64) >> #define BTRFS_IOC_SET_LABEL _IOW(BTRFS_IOCTL_MAGIC, 54, __u64) >> +#define BTRFS_IOC_SUBVOL_GETLABEL _IOWR(BTRFS_IOCTL_MAGIC, 55, __u64) >> +#define BTRFS_IOC_SUBVOL_SETLABEL _IOW(BTRFS_IOCTL_MAGIC, 56, __u64) >> #endif >> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c >> index eb923d0..2a9ae5f 100644 >> --- a/fs/btrfs/root-tree.c >> +++ b/fs/btrfs/root-tree.c >> @@ -35,32 +35,34 @@ void btrfs_read_root_item(struct btrfs_root *root, >> { >> uuid_le uuid; >> int len; >> - int need_reset = 0; >> >> len = btrfs_item_size_nr(eb, slot); >> read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot), >> min_t(int, len, (int)sizeof(*item))); >> - if (len < sizeof(*item)) >> - need_reset = 1; >> - if (!need_reset && btrfs_root_generation(item) >> - != btrfs_root_generation_v2(item)) { >> - if (btrfs_root_generation_v2(item) != 0) { >> - printk(KERN_WARNING "btrfs: mismatching " >> - "generation and generation_v2 " >> - "found in root item. This root " >> - "was probably mounted with an " >> - "older kernel. Resetting all " >> - "new fields.\n"); > > Please argue why removing this without replacement should be a good idea. > >> - } >> - need_reset = 1; >> - } >> - if (need_reset) { >> - memset(&item->generation_v2, 0, >> - sizeof(*item) - offsetof(struct btrfs_root_item, >> - generation_v2)); >> >> - uuid_le_gen(&uuid); >> - memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE); >> + /* when len is gt sizeof(*item) that means its downgrade and >> + the new members won't be touched anyways >> + if len is lt sizeof(*item) its upgrade, we need to take >> + care to set/reset newer members. >> + */ >> + if (len < sizeof(*item)) { >> + /* there is an upgrade need to set/reset the new members >> + assume v1 v2 v3 it can be upgrade from >> + v1 to v2 (set/reset only new members of v2) >> + v2 to v3 (set/reset only new members of v3) >> + v1 to v3 (set/reset new to v1) >> + */ >> + if (btrfs_root_generation(item) != btrfs_root_generation_v2(item)) { >> + //memset(&item->generation_v2, 0, >> + //sizeof(*item) - offsetof(struct btrfs_root_item, generation_v2)); >> + memset(&item->generation_v2, 0, sizeof(*item) - len); >> + uuid_le_gen(&uuid); >> + memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE); >> + } else if (btrfs_root_generation_v2(item) != btrfs_root_generation_v3(item)) { >> + //memset(&item->generation_v3, 0, >> + // sizeof(*item) - offsetof(struct btrfs_root_item, generation_v3)); >> + memset(&item->generation_v3, 0, sizeof(*item) - len); >> + } >> } >> } >> >> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c >> index 04bbfb1..45bff43 100644 >> --- a/fs/btrfs/transaction.c >> +++ b/fs/btrfs/transaction.c >> @@ -1116,6 +1116,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, >> btrfs_set_root_otransid(new_root_item, trans->transid); >> memset(&new_root_item->stime, 0, sizeof(new_root_item->stime)); >> memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime)); >> + memset(new_root_item->label, 0, BTRFS_LABEL_SIZE); >> btrfs_set_root_stransid(new_root_item, 0); >> btrfs_set_root_rtransid(new_root_item, 0); >> >> > > -Jan > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >