Re: Write operation is stuck

From: "Talyansky, Roman" <roman.talyansky@sap.com>
To: Yehuda Sadeh Weinraub <yehudasa@gmail.com>
Cc: Sage Weil <sage@newdream.net>,
	"ceph-devel@lists.sourceforge.net"
	<ceph-devel@lists.sourceforge.net>
Subject: Re: Write operation is stuck
Date: Wed, 24 Feb 2010 14:34:23 +0100	[thread overview]
Message-ID: <C6A64D82E3A5D24B949315CFBC1FA1AD072A3B5200@DEWDFECCR01.wdf.sap.corp> (raw)
In-Reply-To: <a37615151002231011i33a905c8qa338c4018752cc9e@mail.gmail.com>


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Hi Yehuda,

Thanks for the info on the fix. I'll incorporate it into the code and rerun the experiments.
It also seems that the code at that location became a bit more complex - new #if occurred:

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 32)

And consequently the code under #else should be fixed as well.

Thanks,

Roman

From: Yehuda Sadeh Weinraub [mailto:yehudasa@gmail.com]
Sent: Tuesday, February 23, 2010 8:11 PM
To: Talyansky, Roman
Cc: Sage Weil; ceph-devel@lists.sourceforge.net
Subject: Re: [ceph-devel] Write operation is stuck


On Tue, Feb 23, 2010 at 6:11 AM, Talyansky, Roman <roman.talyansky@sap.com<mailto:roman.talyansky@sap.com>> wrote:
Hi Sage,

As you advised us, we switched to the release 0.19 of ceph and ran into another bug in the ceph client. When writing to a file with the O_SYNC flag,  "0" is always returned although the data is written to disk.
This poses a problem in our benchmark which uses the return value as number of bytes written. Also it seems that such behavior infringes the POSIX write() contract.

Yeah, thanks. A fix was pushed to the unstable branch. We will probably start maintaining a stable version that will contain such fixes, but you can apply this in the mean time:

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 2c4ae44..88932c9 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -807,7 +807,7 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov,
        struct ceph_osd_client *osdc = &ceph_client(inode->i_sb)->osdc;
        loff_t endoff = pos + iov->iov_len;
        int got = 0;
-       int ret;
+       int ret, err;

        if (ceph_snap(inode) != CEPH_NOSNAP)
                return -EROFS;
@@ -838,9 +838,12 @@ retry_snap:

                if ((ret >= 0 || ret == -EIOCBQUEUED) &&
                    ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host)
-                    || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL)))
-                       ret = vfs_fsync_range(file, file->f_path.dentry,
+                    || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
+                       err = vfs_fsync_range(file, file->f_path.dentry,
                                              pos, pos + ret - 1, 1);
+                       if (err < 0)
+                               ret = err;
+               }
        }
        if (ret >= 0) {
                spin_lock(&inode->i_lock);



Yehuda

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