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Hi, 'cp -p' in coreutils-5.94-r3 (and most likely others, but this needs verification) doesn't set the value of mtime correctly on files copied to NFS mounts. This problem is likely caused by NFS itself, which seems to update modification times on files after a chmod operation. I believe POSIX defines that mtime should be updated on every change of file content, but I'm not sure on this, so correct me if I'm wrong. Although ultimately NFS might be to blame, the problem seems to be introduced by the recent behaviour in coreutils copy.c, which is outlined below. The behaviour of 'cp' itself is apparent from the following strace output, where it changes file modes after updating the modification time. utimes("/proc/self/fd/4", {1147089451, 552945}) = 0 fchmod(4, 0100600) = 0 Of course this conflicts with the fact that NFS updates mtimes for chmod operations. An easy patch which should be applied to 'src/copy.c' has been provided for an ebuild compile on coreutils-5.94-r3 at: http://www.math.leidenuniv.nl/~rhuizer/coreutils-5.94-r3-copy.c.patch With regards, -- Ronald Huizer
you have to update both copy_reg() and copy_internal() ... ive e-mailed a patch upstream against latest cvs and i'll see what they have to say on the topic
kernel bug which has been fixed already http://lists.gnu.org/archive/html/bug-coreutils/2006-05/msg00060.html
Hi again, I have read the relevant discussion on the link you posted, but am quite convinced this doesn't solve the problems; although admittedly I haven't tested the relevant kernel patch, I have my thoughts on it. This patch seems to resolve issues when caching of NFS writes are involved, where a write occuring before a utimes call would be cached first, and written to disk only after the utimes call. --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -859,11 +859,9 @@ nfs_setattr(struct dentry *dentry, struc lock_kernel(); nfs_begin_data_update(inode); - /* Write all dirty data if we're changing file permissions or size */ - if ((attr->ia_valid & (ATTR_MODE|ATTR_UID|ATTR_GID|ATTR_SIZE)) != 0) { - filemap_write_and_wait(inode->i_mapping); - nfs_wb_all(inode); - } + /* Write all dirty data */ + filemap_write_and_wait(inode->i_mapping); + nfs_wb_all(inode); /* * Return any delegations if we're going to change ACLs */ Reading this patch or the kernel source code makes clear NFS mode changes were always flushed out at this point anyhow, so the change shouldn't matter in this case. What matters is that the fchmod() occurs at a later time in the 'cp' trace than the utimes() call. The test case you outlined in your posting to the list was not a bit confusing, so I have outlined a simple way te verify the problem below: rhuizer@hoornik ~ $ uname -a # Just for the record Linux hoornik 2.6.15-gentoo-r1 #1 PREEMPT Wed Mar 8 11:09:24 CET 2006 i686 AMD Athlon(TM) XP 2000+ GNU/Linux rhuizer@hoornik ~ $ stat breaknfs.c File: `breaknfs.c' Size: 803 Blocks: 8 IO Block: 32768 regular file Device: 12h/18d Inode: 58327432 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 669/ rhuizer) Gid: ( 501/ admins) Access: 2006-05-06 18:09:56.000000000 +0200 Modify: 2005-09-13 11:34:59.000000000 +0200 Change: 2005-09-13 11:34:59.000000000 +0200 rhuizer@hoornik ~ $ cp -p breaknfs.c new.c rhuizer@hoornik ~ $ stat new.c File: `new.c' Size: 803 Blocks: 8 IO Block: 32768 regular file Device: 12h/18d Inode: 39370836 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 669/ rhuizer) Gid: ( 501/ admins) Access: 2006-05-06 18:09:56.000000000 +0200 Modify: 2006-05-09 16:33:18.233727766 +0200 Change: 2006-05-09 16:33:18.237727944 +0200 From this it should be evident that the resolution order of 'cp -p' conflicts with NFS updating timestamps on fchmod(). The remark that cp should be able to provide support for ownership transfers might be appropriate, but does that argument hold true for only the modes of a file? It might be possible to place the utimes() call after the fchmod() and before the chown(). With regards, -- Ronald Huizer
not a bug in coreutils
Please confirm that this bug exists in the latest development kernel, currently 2.6.17-rc3
it exists in 2.6.16.9 for sure
Trying this on 2.6.17-rc4 seems a whole lot better; at least the modification and access times are now shown correctly (disregarding microsecond truncation). Seems to be resolved for me. With regards, -- Ronald Huizer rhuizer@hoornik ~ $ uname -a Linux hoornik 2.6.17-rc4 #1 PREEMPT Tue May 23 09:43:42 CEST 2006 i686 AMD Athlon(TM) XP 2000+ GNU/Linux rhuizer@hoornik ~ $ stat breaknfs.c File: `breaknfs.c' Size: 803 Blocks: 8 IO Block: 32768 regular file Device: 12h/18d Inode: 58327432 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 669/ rhuizer) Gid: ( 501/ admins) Access: 2006-05-23 10:50:12.779180516 +0200 Modify: 2005-09-13 11:34:59.000000000 +0200 Change: 2005-09-13 11:34:59.000000000 +0200 rhuizer@hoornik ~ $ cp -p breaknfs.c foo.c rhuizer@hoornik ~ $ stat foo.c File: `foo.c' Size: 803 Blocks: 8 IO Block: 32768 regular file Device: 12h/18d Inode: 58327333 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 669/ rhuizer) Gid: ( 501/ admins) Access: 2006-05-23 10:50:12.779180000 +0200 Modify: 2005-09-13 11:34:59.000000000 +0200 Change: 2006-05-23 10:52:47.612671133 +0200
I'd like to backport the fix, but I can't see which patch in 2.6.17 solves this. The only real suspect is this one: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff_plain;h=755c1e20cd2ad56e5c567fa05769eb98a3eef72b;hp=7bab377fcb495ee2e5a1cd69d235f8d84c76e3af Would you mind patching 2.6.16 with that and seeing if that fixes it, just in case your understanding is incorrect?
> I'd like to backport the fix, but I can't see which patch in 2.6.17 solves > this. The only real suspect is this one: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff_plain;h=755c1e20cd2ad56e5c567fa05769eb98a3eef72b;hp=7bab377fcb495ee2e5a1cd69d235f8d84c76e3af You are right, thanks for asking this. I didn't misunderstand the patch, I misunderstood the nature of the bug, afaics now NFS never explicitly updated mtimes on fchown(), but didn't sync out the blocks after setting [am]time attributes immediatly. I was puzzled at first why this would trigger with coreutils before patching it and not after, but it seems similar to the following: In the first situation of "utimes() / fchown() / close()" we have fchown() synching out disk blocks after the utimes attribute has been set, thus killing mtime, and in the second situation of "fchown() / utimes() / close()" we have fchown() flushing out all the pending data, updating mtime, then utimes() setting it explicitly, then close() not flushing pending blocks since there is nothing to flush. Anyway, this should (hopefully) settle and clarify things and allow you to backport the patch easily. Sorry for the additional trouble. With kind regards, -- Ronald Huizer
Fixed in gentoo-sources-2.6.16-gentoo-r9 / genpatches-2.6.16-11
