| Message ID | 1341919719-13825-1-git-send-email-liubo2009@cn.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Liu, can you pls explain this a bit more to me. I see in my fs that there are (FREE_SPACE,0, offset) items in the root tree. It seems that offset here is the objectid of the appropriate BLOCK_GROUP_ITEM. Also, I see that each FREE_SPACE points at some INODE_ITEM within the root tree, and this INODE_ITEM also has extents. I presume that these extents contain the free space cache in some format, is that correct? However, I don't see any FREE_INO entries, what are they? Are they perhaps used only when "inode_cache" mount option is used, so inode numbers are not always incremented in btrfs_find_free_ino(), but smaller unused numbers are reused? Also, I don't see anywhere BTRFS_BTREE_INODE_OBJECTID in the tree root tree. So what is this "btree inode" that you mention? Thanks, Alex. On Tue, Jul 10, 2012 at 2:28 PM, Liu Bo <liubo2009@cn.fujitsu.com> wrote: > For btree inode, its root is also 'tree root', so btree inode can be > misunderstood as a free space inode. > > We should add one more check for btree inode. > > Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> > --- > fs/btrfs/btrfs_inode.h | 6 ++++-- > 1 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h > index 12394a9..b168238 100644 > --- a/fs/btrfs/btrfs_inode.h > +++ b/fs/btrfs/btrfs_inode.h > @@ -194,8 +194,10 @@ static inline void btrfs_i_size_write(struct inode *inode, u64 size) > static inline bool btrfs_is_free_space_inode(struct btrfs_root *root, > struct inode *inode) > { > - if (root == root->fs_info->tree_root || > - BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) > + if (root == root->fs_info->tree_root && > + btrfs_ino(inode) != BTRFS_BTREE_INODE_OBJECTID) > + return true; > + if (BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) > return true; > return false; > } > -- > 1.6.5.2 > > -- > 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 -- 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
On 07/18/2012 06:02 PM, Alex Lyakas wrote: > Hi Liu, > can you pls explain this a bit more to me. > I see in my fs that there are (FREE_SPACE,0, offset) items in the root > tree. It seems that offset here is the objectid of the appropriate > BLOCK_GROUP_ITEM. Also, I see that each FREE_SPACE points at some > INODE_ITEM within the root tree, and this INODE_ITEM also has extents. > I presume that these extents contain the free space cache in some > format, is that correct? > More or less. As its name shows, a free space inode's data (you name it extents) consists of free space info, meanwhile, a free space inode is issued to a block group, so the free space info actually stands for free space in the block group: |<- a block group len ->| |----vvv----vvv-------vvv-----| 'v' : occupied. '-' : available. (free space) these free space info are indexed in a rbtree in memory, and each entry has [start, len]. > However, I don't see any FREE_INO entries, what are they? Are they > perhaps used only when "inode_cache" mount option is used, so inode > numbers are not always incremented in btrfs_find_free_ino(), but > smaller unused numbers are reused? > Yes, that's what it is used for. > Also, I don't see anywhere BTRFS_BTREE_INODE_OBJECTID in the tree root > tree. So what is this "btree inode" that you mention? > The code refers to disk_io.c, in the function 'open_ctree()' you can see the definition. Basically btree inode's data stands for btrfs's metadata, I think you can find something in btrfs's wiki page? And thanks for your energy on btrfs! :) thanks, liubo > Thanks, > Alex. > > > On Tue, Jul 10, 2012 at 2:28 PM, Liu Bo <liubo2009@cn.fujitsu.com> wrote: >> For btree inode, its root is also 'tree root', so btree inode can be >> misunderstood as a free space inode. >> >> We should add one more check for btree inode. >> >> Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> >> --- >> fs/btrfs/btrfs_inode.h | 6 ++++-- >> 1 files changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h >> index 12394a9..b168238 100644 >> --- a/fs/btrfs/btrfs_inode.h >> +++ b/fs/btrfs/btrfs_inode.h >> @@ -194,8 +194,10 @@ static inline void btrfs_i_size_write(struct inode *inode, u64 size) >> static inline bool btrfs_is_free_space_inode(struct btrfs_root *root, >> struct inode *inode) >> { >> - if (root == root->fs_info->tree_root || >> - BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) >> + if (root == root->fs_info->tree_root && >> + btrfs_ino(inode) != BTRFS_BTREE_INODE_OBJECTID) >> + return true; >> + if (BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) >> return true; >> return false; >> } >> -- >> 1.6.5.2 >> >> -- >> 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 > -- > 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 > -- 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
On Wed, Jul 18, 2012 at 3:02 PM, Liu Bo <liubo2009@cn.fujitsu.com> wrote: > On 07/18/2012 06:02 PM, Alex Lyakas wrote: > > More or less. > > As its name shows, a free space inode's data (you name it extents) consists of > free space info, meanwhile, a free space inode is issued to a block group, > so the free space info actually stands for free space in the block group: > > |<- a block group len ->| > |----vvv----vvv-------vvv-----| > > 'v' : occupied. > '-' : available. (free space) > > these free space info are indexed in a rbtree in memory, and each entry has [start, len]. Thanks, it makes sense with what I saw in the code, just could not figure how this free-space inode's data is being read into memory. > >> Also, I don't see anywhere BTRFS_BTREE_INODE_OBJECTID in the tree root >> tree. So what is this "btree inode" that you mention? >> > > > The code refers to disk_io.c, in the function 'open_ctree()' you can see the definition. > I saw it there, but not on disk. So now I see that it's kind of a special "top" inode, used for ... something, and this inode is not stored anywhere on-disk. Thanks, now I understand your patch. Also, I understand now that FREE_INO items sit in the subvolume file tree (and perhaps also in the root tree), because they need to track free inos for distinct ino spaces. > Basically btree inode's data stands for btrfs's metadata, I think you can find something > in btrfs's wiki page? > > > And thanks for your energy on btrfs! :) Thanks for helping. Alex. -- 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
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h index 12394a9..b168238 100644 --- a/fs/btrfs/btrfs_inode.h +++ b/fs/btrfs/btrfs_inode.h @@ -194,8 +194,10 @@ static inline void btrfs_i_size_write(struct inode *inode, u64 size) static inline bool btrfs_is_free_space_inode(struct btrfs_root *root, struct inode *inode) { - if (root == root->fs_info->tree_root || - BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) + if (root == root->fs_info->tree_root && + btrfs_ino(inode) != BTRFS_BTREE_INODE_OBJECTID) + return true; + if (BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) return true; return false; }
For btree inode, its root is also 'tree root', so btree inode can be misunderstood as a free space inode. We should add one more check for btree inode. Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> --- fs/btrfs/btrfs_inode.h | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)