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    SubjectRe: [linux-cifs-client] Re: [PATCH] fs/cifs: send SMB_COM_FLUSH in cifs_fsync
    On Sun, 22 Feb 2009 22:07:05 -0600
    Steve French <smfrench@gmail.com> wrote:

    > diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
    > index d43e0fe..b33c841 100644
    > --- a/fs/cifs/CHANGES
    > +++ b/fs/cifs/CHANGES
    > @@ -8,7 +8,9 @@ user's smb session. This fix allows cifs to mount multiple times to the
    > same server with different userids without risking invalidating earlier
    > established security contexts. fsync now sends SMB Flush operation
    > to better ensure that we wait for server to write all of the data to
    > -server disk (not just write it over the network).
    > +server disk (not just write it over the network). Add new mount
    > +parameter to allow user to disable sending the (slow) SMB flush on
    > +fsync if desired (fsync still flushes all cached write data to the server).
    >
    > Version 1.56
    > ------------
    > diff --git a/fs/cifs/README b/fs/cifs/README
    > index da4515e..6436966 100644
    > --- a/fs/cifs/README
    > +++ b/fs/cifs/README
    > @@ -472,6 +472,19 @@ A partial list of the supported mount options follows:
    > even if the cifs server would support posix advisory locks.
    > "forcemand" is accepted as a shorter form of this mount
    > option.
    > + nostrictsync If this mount option is set, when an application does an
    > + fsync call then the cifs client does not send an SMB Flush
    > + to the server (to force the server to write all dirty data
    > + for this file immediately to disk), although cifs still sends
    > + all dirty (cached) file data to the server and waits for the
    > + server to respond to the write write. Since SMB Flush can be
    > + very slow, and some servers may be reliable enough (to risk
    > + delaying slightly flushing the data to disk on the server),
    > + turning on this option may be useful to improve performance for
    > + applications that fsync too much, at a small risk of server
    > + crash. If this mount option is not set, by default cifs will
    > + send an SMB flush request (and wait for a response) on every
    > + fsync call.
    > nodfs Disable DFS (global name space support) even if the
    > server claims to support it. This can help work around
    > a problem with parsing of DFS paths with Samba server
    > diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
    > index c4c306f..e9f177b 100644
    > --- a/fs/cifs/cifs_fs_sb.h
    > +++ b/fs/cifs/cifs_fs_sb.h
    > @@ -32,6 +32,7 @@
    > #define CIFS_MOUNT_OVERR_GID 0x800 /* override gid returned from server */
    > #define CIFS_MOUNT_DYNPERM 0x1000 /* allow in-memory only mode setting */
    > #define CIFS_MOUNT_NOPOSIXBRL 0x2000 /* mandatory not posix byte range lock */
    > +#define CIFS_MOUNT_NO_SSYNC 0x4000 /* don't do slow SMBflush on every sync*/
    >
    > struct cifs_sb_info {
    > struct cifsTconInfo *tcon; /* primary mount */
    > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
    > index da0f4ff..18e84a4 100644
    > --- a/fs/cifs/connect.c
    > +++ b/fs/cifs/connect.c
    > @@ -95,6 +95,7 @@ struct smb_vol {
    > bool local_lease:1; /* check leases only on local system, not remote */
    > bool noblocksnd:1;
    > bool noautotune:1;
    > + bool nostrictsync:1; /* do not force expensive SMBflush on every sync */
    > unsigned int rsize;
    > unsigned int wsize;
    > unsigned int sockopt;
    > @@ -1274,6 +1275,10 @@ cifs_parse_mount_options(char *options, const char *devname,
    > vol->intr = 0;
    > } else if (strnicmp(data, "intr", 4) == 0) {
    > vol->intr = 1;
    > + } else if (strnicmp(data, "nostrictsync", 12) == 0) {
    > + vol->nostrictsync = 1;
    > + } else if (strnicmp(data, "strictsync", 10) == 0) {
    > + vol->nostrictsync = 0;
    > } else if (strnicmp(data, "serverino", 7) == 0) {
    > vol->server_ino = 1;
    > } else if (strnicmp(data, "noserverino", 9) == 0) {
    > @@ -2160,6 +2165,8 @@ static void setup_cifs_sb(struct smb_vol *pvolume_info,
    > cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_UNX_EMUL;
    > if (pvolume_info->nobrl)
    > cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_BRL;
    > + if (pvolume_info->nostrictsync)
    > + cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_SSYNC;
    > if (pvolume_info->mand_lock)
    > cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NOPOSIXBRL;
    > if (pvolume_info->cifs_acl)
    > diff --git a/fs/cifs/file.c b/fs/cifs/file.c
    > index 83b4741..6411f5f 100644
    > --- a/fs/cifs/file.c
    > +++ b/fs/cifs/file.c
    > @@ -1538,7 +1538,8 @@ int cifs_fsync(struct file *file, struct dentry *dentry, int datasync)
    > rc = CIFS_I(inode)->write_behind_rc;
    > CIFS_I(inode)->write_behind_rc = 0;
    > tcon = CIFS_SB(inode->i_sb)->tcon;
    > - if (!rc && tcon && smbfile)
    > + if (!rc && tcon && smbfile &&
    > + !(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_SSYNC))
    ^^^^^^^
    This doesn't compile as there is no cifs_sb defined in this function...

    > rc = CIFSSMBFlush(xid, tcon, smbfile->netfid);
    > }
    >


    --
    Jeff Layton <jlayton@redhat.com>


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