On 08/17/2012 10:59 PM, David Sterba wrote: > On Fri, Aug 17, 2012 at 09:45:20AM +0800, Liu Bo wrote: >> On 08/15/2012 06:12 PM, Lluís Batlle i Rossell wrote: >>> some time ago we discussed on #btrfs that the nocow attribute for files wasn't >>> working (around 3.3 or 3.4 kernels). That was evident by files fragmenting even >>> with the attribute set. >>> >>> Chris mentioned to find a fix quickly for that, and posted some lines of change >>> into irc. But recently someone mentioned that 3.6-rc looks like still not >>> respecting nocow for files. >>> >>> Is there really a fix upstream for that? Do nocow attribute on files work for >>> anyone already? >>> >> >> Dave had post a patch to fix it but only enabling NOCOW with zero sized file. >> >> FYI, the patch is http://article.gmane.org/gmane.comp.file-systems.btrfs/17351 >> >> With the patch, you don't need to mount with nodatacow any more :) >> >> And why it is only for only zero sized file: >> http://permalink.gmane.org/gmane.comp.file-systems.btrfs/18046 > > the original patch http://permalink.gmane.org/gmane.comp.file-systems.btrfs/18031 > did two things, the reasoning why it is not allowed to set nodatasum in > general applies only to the second hunk but this > > @@ -139,7 +139,7 @@ void btrfs_inherit_iflags(struct inode *inode, struct inode *dir) > } > > if (flags & BTRFS_INODE_NODATACOW) > - BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW; > + BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW | BTRFS_INODE_NODATASUM; > > btrfs_update_iflags(inode); > } > --- > > is sufficient to create nocow files via a directory with NOCOW attribute > set, and all new files will inherit it (they are automatically > zero-sized so it's safe). This usecase is similar to setting the > COMPRESS attribute on a directory and all new files will inherit the > flag. > > If Andrei wants to resend just this particular hunk, I'm giving it my ACK. > IMO the following is better, just make use of the original check. If you agree with this, I'll send it as a patch :) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 6e8f416..d4e58df 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4721,8 +4721,10 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans, if (btrfs_test_opt(root, NODATASUM)) BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM; if (btrfs_test_opt(root, NODATACOW) || - (BTRFS_I(dir)->flags & BTRFS_INODE_NODATACOW)) + (BTRFS_I(dir)->flags & BTRFS_INODE_NODATACOW)) { BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW; + BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM; + } } insert_inode_hash(inode); > > david > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > 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@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
