| Message ID | 1393859506-10889-1-git-send-email-sprabhu@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 3 Mar 2014 15:11:46 +0000 Sachin Prabhu <sprabhu@redhat.com> wrote: > Problem reported in Red Hat bz 1040329 for strict writes where we cache > only when we hold oplock and write direct to the server when we don't. > > When we receive an oplock break, we first change the oplock value for > the inode in cifsInodeInfo->oplock to indicate that we no longer hold > the oplock before we enqueue a task to flush changes to the backing > device. Once we have completed flushing the changes, we return the > oplock to the server. > > There are 2 ways here where we can have data corruption > 1) While we flush changes to the backing device as part of the oplock > break, we can have processes write to the file. These writes check for > the oplock, find none and attempt to write directly to the server. > These direct writes made while we are flushing from cache could be > overwritten by data being flushed from the cache causing data > corruption. > 2) While a thread runs in cifs_strict_writev, the machine could receive > and process an oplock break after the thread has checked the oplock and > found that it allows us to cache and before we have made changes to the > cache. In that case, we end up with a dirty page in cache when we > shouldn't have any. This will be flushed later and will overwrite all > subsequent writes to the part of the file represented by this page. > > Before making any writes to the server, we need to confirm that we are > not in the process of flushing data to the server and if we are, we > should wait until the process is complete before we attempt the write. > We should also wait for existing writes to complete before we process > an oplock break request which changes oplock values. > > Signed-off-by: Sachin Prabhu <sprabhu@redhat.com> > --- > fs/cifs/cifsfs.c | 14 +++++++++- > fs/cifs/cifsglob.h | 9 +++++++ > fs/cifs/cifsproto.h | 3 +++ > fs/cifs/file.c | 32 ++++++++++++++++++++--- > fs/cifs/misc.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++-- > 5 files changed, 126 insertions(+), 6 deletions(-) > > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c > index 849f613..6d5cf79 100644 > --- a/fs/cifs/cifsfs.c > +++ b/fs/cifs/cifsfs.c > @@ -253,6 +253,11 @@ cifs_alloc_inode(struct super_block *sb) > cifs_set_oplock_level(cifs_inode, 0); > cifs_inode->delete_pending = false; > cifs_inode->invalid_mapping = false; > + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cifs_inode->flags); > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cifs_inode->flags); > + clear_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cifs_inode->flags); > + mutex_init(&cifs_inode->writers_lock); > + cifs_inode->writers = 0; > cifs_inode->vfs_inode.i_blkbits = 14; /* 2**14 = CIFS_MAX_MSGSIZE */ > cifs_inode->server_eof = 0; > cifs_inode->uniqueid = 0; > @@ -731,19 +736,26 @@ static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov, > unsigned long nr_segs, loff_t pos) > { > struct inode *inode = file_inode(iocb->ki_filp); > + struct cifsInodeInfo *cinode = CIFS_I(inode); > ssize_t written; > int rc; > > + written = cifs_get_writer(cinode); > + if (written) > + return written; > + > written = generic_file_aio_write(iocb, iov, nr_segs, pos); > > if (CIFS_CACHE_WRITE(CIFS_I(inode))) > - return written; > + goto out; > > rc = filemap_fdatawrite(inode->i_mapping); > if (rc) > cifs_dbg(FYI, "cifs_file_aio_write: %d rc on %p inode\n", > rc, inode); > > +out: > + cifs_put_writer(cinode); > return written; > } > > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h > index f918a99..1a3a88d 100644 > --- a/fs/cifs/cifsglob.h > +++ b/fs/cifs/cifsglob.h > @@ -1096,6 +1096,15 @@ struct cifsInodeInfo { > unsigned int epoch; /* used to track lease state changes */ > bool delete_pending; /* DELETE_ON_CLOSE is set */ > bool invalid_mapping; /* pagecache is invalid */ > + unsigned long flags; > +#define CIFS_INODE_PENDING_OPLOCK_BREAK 0 /* oplock break in progress */ > +#define CIFS_INODE_PENDING_WRITERS 1 /* Writing operations in progress */ > +#define CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2 2 /* nit: please align the values for readability. Probably also good to wrap them in parenthesis -- e.g. "(1)". > + * We have received a request to > + * downgrade oplock to L2 oplock > + */ > + struct mutex writers_lock; I don't see any reason to use a mutex here. There are no critical sections that sleep AFAICT. Why not use a spinlock which would be smaller (4 bytes vs. 40 bytes on my x86_64 box)? In fact, you could even consider just using the i_lock for this (though I'd understand if you wanted to use your own). > + unsigned int writers; /* Number of writers on this inode */ > unsigned long time; /* jiffies of last update of inode */ > u64 server_eof; /* current file size on server -- protected by i_lock */ > u64 uniqueid; /* server inode number */ > diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h > index 2c29db6..fa41676 100644 > --- a/fs/cifs/cifsproto.h > +++ b/fs/cifs/cifsproto.h > @@ -127,6 +127,9 @@ extern u64 cifs_UnixTimeToNT(struct timespec); > extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time, > int offset); > extern void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock); > +extern int cifs_get_writer(struct cifsInodeInfo *cinode); > +extern void cifs_put_writer(struct cifsInodeInfo *cinode); > +extern void cifs_done_oplock_break(struct cifsInodeInfo *cinode); > extern int cifs_unlock_range(struct cifsFileInfo *cfile, > struct file_lock *flock, const unsigned int xid); > extern int cifs_push_mandatory_locks(struct cifsFileInfo *cfile); > diff --git a/fs/cifs/file.c b/fs/cifs/file.c > index 5a5a872..5a94d7b 100644 > --- a/fs/cifs/file.c > +++ b/fs/cifs/file.c > @@ -2580,12 +2580,20 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, > struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); > ssize_t written; > > + written = cifs_get_writer(cinode); > + if (written) > + return written; > + > if (CIFS_CACHE_WRITE(cinode)) { > if (cap_unix(tcon->ses) && > (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) > - && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) > - return generic_file_aio_write(iocb, iov, nr_segs, pos); > - return cifs_writev(iocb, iov, nr_segs, pos); > + && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) { > + written = generic_file_aio_write( > + iocb, iov, nr_segs, pos); > + goto out; > + } > + written = cifs_writev(iocb, iov, nr_segs, pos); > + goto out; > } > /* > * For non-oplocked files in strict cache mode we need to write the data > @@ -2605,6 +2613,8 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, > inode); > cinode->oplock = 0; > } > +out: > + cifs_put_writer(cinode); > return written; > } > > @@ -3616,6 +3626,13 @@ static int cifs_launder_page(struct page *page) > return rc; > } > > +static int > +cifs_oplock_break_wait(void *unused) > +{ > + schedule(); > + return signal_pending(current) ? -ERESTARTSYS : 0; > +} > + This wait will just be used from cifs_oplock_break(), right? Since that's a workqueue job, then we don't expect any signals there. I think there's no need for checking signal_pending(). Just calling schedule() is probably fine. > void cifs_oplock_break(struct work_struct *work) > { > struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo, > @@ -3625,6 +3642,14 @@ void cifs_oplock_break(struct work_struct *work) > struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); > int rc = 0; > > + wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS, > + cifs_oplock_break_wait, TASK_UNINTERRUPTIBLE); > + > + if (test_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cinode->flags)) > + cifs_set_oplock_level(cinode, OPLOCK_READ); > + else > + cifs_set_oplock_level(cinode, 0); > + > if (!CIFS_CACHE_WRITE(cinode) && CIFS_CACHE_READ(cinode) && > cifs_has_mand_locks(cinode)) { > cifs_dbg(FYI, "Reset oplock to None for inode=%p due to mand locks\n", > @@ -3661,6 +3686,7 @@ void cifs_oplock_break(struct work_struct *work) > cinode); > cifs_dbg(FYI, "Oplock release rc = %d\n", rc); > } > + cifs_done_oplock_break(cinode); > } > > /* > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c > index 2f9f379..55b26bd 100644 > --- a/fs/cifs/misc.c > +++ b/fs/cifs/misc.c > @@ -466,8 +466,22 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv) > cifs_dbg(FYI, "file id match, oplock break\n"); > pCifsInode = CIFS_I(netfile->dentry->d_inode); > > - cifs_set_oplock_level(pCifsInode, > - pSMB->OplockLevel ? OPLOCK_READ : 0); > + set_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, > + &pCifsInode->flags); > + > + /* > + * Set flag if the server downgrades the oplock > + * to L2 else clear. > + */ > + if (pSMB->OplockLevel) > + set_bit( > + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, > + &pCifsInode->flags); > + else > + clear_bit( > + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, > + &pCifsInode->flags); > + > queue_work(cifsiod_wq, > &netfile->oplock_break); > netfile->oplock_break_cancelled = false; > @@ -551,6 +565,62 @@ void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock) > cinode->oplock = 0; > } > > +static int > +cifs_oplock_break_wait(void *unused) > +{ > + schedule(); > + return signal_pending(current) ? -ERESTARTSYS : 0; > +} > + > +/* > + * We wait for oplock breaks to be processed before we attempt to perform > + * writes. > + */ > +int cifs_get_writer(struct cifsInodeInfo *cinode) > +{ > + int rc; > + > +start: > + rc = wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK, > + cifs_oplock_break_wait, TASK_KILLABLE); > + if (rc) > + return rc; > + > + mutex_lock(&cinode->writers_lock); > + if (!cinode->writers) > + set_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > + cinode->writers++; > + /* Check to see if we have started servicing an oplock break */ > + if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) { > + cinode->writers--; > + if (cinode->writers == 0) { > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > + } > + mutex_unlock(&cinode->writers_lock); > + goto start; > + } > + mutex_unlock(&cinode->writers_lock); > + return 0; > +} > + > +void cifs_put_writer(struct cifsInodeInfo *cinode) > +{ > + mutex_lock(&cinode->writers_lock); > + cinode->writers--; > + if (cinode->writers == 0) { > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > + } > + mutex_unlock(&cinode->writers_lock); > +} > + > +void cifs_done_oplock_break(struct cifsInodeInfo *cinode) > +{ > + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK); > +} > + > bool > backup_cred(struct cifs_sb_info *cifs_sb) > { Looks good otherwise, and definitely something we need to fix since it's a data corruptor. The final version of this should probably go to stable for that reason...
On Tue, 2014-03-04 at 10:16 -0500, Jeff Layton wrote: > On Mon, 3 Mar 2014 15:11:46 +0000 > Sachin Prabhu <sprabhu@redhat.com> wrote: > > > Problem reported in Red Hat bz 1040329 for strict writes where we cache > > only when we hold oplock and write direct to the server when we don't. > > > > When we receive an oplock break, we first change the oplock value for > > the inode in cifsInodeInfo->oplock to indicate that we no longer hold > > the oplock before we enqueue a task to flush changes to the backing > > device. Once we have completed flushing the changes, we return the > > oplock to the server. > > > > There are 2 ways here where we can have data corruption > > 1) While we flush changes to the backing device as part of the oplock > > break, we can have processes write to the file. These writes check for > > the oplock, find none and attempt to write directly to the server. > > These direct writes made while we are flushing from cache could be > > overwritten by data being flushed from the cache causing data > > corruption. > > 2) While a thread runs in cifs_strict_writev, the machine could receive > > and process an oplock break after the thread has checked the oplock and > > found that it allows us to cache and before we have made changes to the > > cache. In that case, we end up with a dirty page in cache when we > > shouldn't have any. This will be flushed later and will overwrite all > > subsequent writes to the part of the file represented by this page. > > > > Before making any writes to the server, we need to confirm that we are > > not in the process of flushing data to the server and if we are, we > > should wait until the process is complete before we attempt the write. > > We should also wait for existing writes to complete before we process > > an oplock break request which changes oplock values. > > > > Signed-off-by: Sachin Prabhu <sprabhu@redhat.com> > > --- > > fs/cifs/cifsfs.c | 14 +++++++++- > > fs/cifs/cifsglob.h | 9 +++++++ > > fs/cifs/cifsproto.h | 3 +++ > > fs/cifs/file.c | 32 ++++++++++++++++++++--- > > fs/cifs/misc.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++-- > > 5 files changed, 126 insertions(+), 6 deletions(-) > > > > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c > > index 849f613..6d5cf79 100644 > > --- a/fs/cifs/cifsfs.c > > +++ b/fs/cifs/cifsfs.c > > @@ -253,6 +253,11 @@ cifs_alloc_inode(struct super_block *sb) > > cifs_set_oplock_level(cifs_inode, 0); > > cifs_inode->delete_pending = false; > > cifs_inode->invalid_mapping = false; > > + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cifs_inode->flags); > > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cifs_inode->flags); > > + clear_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cifs_inode->flags); > > + mutex_init(&cifs_inode->writers_lock); > > + cifs_inode->writers = 0; > > cifs_inode->vfs_inode.i_blkbits = 14; /* 2**14 = CIFS_MAX_MSGSIZE */ > > cifs_inode->server_eof = 0; > > cifs_inode->uniqueid = 0; > > @@ -731,19 +736,26 @@ static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov, > > unsigned long nr_segs, loff_t pos) > > { > > struct inode *inode = file_inode(iocb->ki_filp); > > + struct cifsInodeInfo *cinode = CIFS_I(inode); > > ssize_t written; > > int rc; > > > > + written = cifs_get_writer(cinode); > > + if (written) > > + return written; > > + > > written = generic_file_aio_write(iocb, iov, nr_segs, pos); > > > > if (CIFS_CACHE_WRITE(CIFS_I(inode))) > > - return written; > > + goto out; > > > > rc = filemap_fdatawrite(inode->i_mapping); > > if (rc) > > cifs_dbg(FYI, "cifs_file_aio_write: %d rc on %p inode\n", > > rc, inode); > > > > +out: > > + cifs_put_writer(cinode); > > return written; > > } > > > > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h > > index f918a99..1a3a88d 100644 > > --- a/fs/cifs/cifsglob.h > > +++ b/fs/cifs/cifsglob.h > > @@ -1096,6 +1096,15 @@ struct cifsInodeInfo { > > unsigned int epoch; /* used to track lease state changes */ > > bool delete_pending; /* DELETE_ON_CLOSE is set */ > > bool invalid_mapping; /* pagecache is invalid */ > > + unsigned long flags; > > +#define CIFS_INODE_PENDING_OPLOCK_BREAK 0 /* oplock break in progress */ > > +#define CIFS_INODE_PENDING_WRITERS 1 /* Writing operations in progress */ > > +#define CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2 2 /* > > nit: please align the values for readability. Probably also good to > wrap them in parenthesis -- e.g. "(1)". > > > + * We have received a request to > > + * downgrade oplock to L2 oplock > > + */ > > + struct mutex writers_lock; > > I don't see any reason to use a mutex here. There are no critical > sections that sleep AFAICT. Why not use a spinlock which would be > smaller (4 bytes vs. 40 bytes on my x86_64 box)? > > In fact, you could even consider just using the i_lock for this (though > I'd understand if you wanted to use your own). > > > + unsigned int writers; /* Number of writers on this inode */ > > unsigned long time; /* jiffies of last update of inode */ > > u64 server_eof; /* current file size on server -- protected by i_lock */ > > u64 uniqueid; /* server inode number */ > > diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h > > index 2c29db6..fa41676 100644 > > --- a/fs/cifs/cifsproto.h > > +++ b/fs/cifs/cifsproto.h > > @@ -127,6 +127,9 @@ extern u64 cifs_UnixTimeToNT(struct timespec); > > extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time, > > int offset); > > extern void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock); > > +extern int cifs_get_writer(struct cifsInodeInfo *cinode); > > +extern void cifs_put_writer(struct cifsInodeInfo *cinode); > > +extern void cifs_done_oplock_break(struct cifsInodeInfo *cinode); > > extern int cifs_unlock_range(struct cifsFileInfo *cfile, > > struct file_lock *flock, const unsigned int xid); > > extern int cifs_push_mandatory_locks(struct cifsFileInfo *cfile); > > diff --git a/fs/cifs/file.c b/fs/cifs/file.c > > index 5a5a872..5a94d7b 100644 > > --- a/fs/cifs/file.c > > +++ b/fs/cifs/file.c > > @@ -2580,12 +2580,20 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, > > struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); > > ssize_t written; > > > > + written = cifs_get_writer(cinode); > > + if (written) > > + return written; > > + > > if (CIFS_CACHE_WRITE(cinode)) { > > if (cap_unix(tcon->ses) && > > (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) > > - && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) > > - return generic_file_aio_write(iocb, iov, nr_segs, pos); > > - return cifs_writev(iocb, iov, nr_segs, pos); > > + && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) { > > + written = generic_file_aio_write( > > + iocb, iov, nr_segs, pos); > > + goto out; > > + } > > + written = cifs_writev(iocb, iov, nr_segs, pos); > > + goto out; > > } > > /* > > * For non-oplocked files in strict cache mode we need to write the data > > @@ -2605,6 +2613,8 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, > > inode); > > cinode->oplock = 0; > > } > > +out: > > + cifs_put_writer(cinode); > > return written; > > } > > > > @@ -3616,6 +3626,13 @@ static int cifs_launder_page(struct page *page) > > return rc; > > } > > > > +static int > > +cifs_oplock_break_wait(void *unused) > > +{ > > + schedule(); > > + return signal_pending(current) ? -ERESTARTSYS : 0; > > +} > > + > > This wait will just be used from cifs_oplock_break(), right? Since > that's a workqueue job, then we don't expect any signals there. I think > there's no need for checking signal_pending(). Just calling schedule() > is probably fine. > > > void cifs_oplock_break(struct work_struct *work) > > { > > struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo, > > @@ -3625,6 +3642,14 @@ void cifs_oplock_break(struct work_struct *work) > > struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); > > int rc = 0; > > > > + wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS, > > + cifs_oplock_break_wait, TASK_UNINTERRUPTIBLE); > > + > > + if (test_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cinode->flags)) > > + cifs_set_oplock_level(cinode, OPLOCK_READ); > > + else > > + cifs_set_oplock_level(cinode, 0); > > + > > if (!CIFS_CACHE_WRITE(cinode) && CIFS_CACHE_READ(cinode) && > > cifs_has_mand_locks(cinode)) { > > cifs_dbg(FYI, "Reset oplock to None for inode=%p due to mand locks\n", > > @@ -3661,6 +3686,7 @@ void cifs_oplock_break(struct work_struct *work) > > cinode); > > cifs_dbg(FYI, "Oplock release rc = %d\n", rc); > > } > > + cifs_done_oplock_break(cinode); > > } > > > > /* > > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c > > index 2f9f379..55b26bd 100644 > > --- a/fs/cifs/misc.c > > +++ b/fs/cifs/misc.c > > @@ -466,8 +466,22 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv) > > cifs_dbg(FYI, "file id match, oplock break\n"); > > pCifsInode = CIFS_I(netfile->dentry->d_inode); > > > > - cifs_set_oplock_level(pCifsInode, > > - pSMB->OplockLevel ? OPLOCK_READ : 0); > > + set_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, > > + &pCifsInode->flags); > > + > > + /* > > + * Set flag if the server downgrades the oplock > > + * to L2 else clear. > > + */ > > + if (pSMB->OplockLevel) > > + set_bit( > > + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, > > + &pCifsInode->flags); > > + else > > + clear_bit( > > + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, > > + &pCifsInode->flags); > > + > > queue_work(cifsiod_wq, > > &netfile->oplock_break); > > netfile->oplock_break_cancelled = false; > > @@ -551,6 +565,62 @@ void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock) > > cinode->oplock = 0; > > } > > > > +static int > > +cifs_oplock_break_wait(void *unused) > > +{ > > + schedule(); > > + return signal_pending(current) ? -ERESTARTSYS : 0; > > +} > > + > > +/* > > + * We wait for oplock breaks to be processed before we attempt to perform > > + * writes. > > + */ > > +int cifs_get_writer(struct cifsInodeInfo *cinode) > > +{ > > + int rc; > > + > > +start: > > + rc = wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK, > > + cifs_oplock_break_wait, TASK_KILLABLE); > > + if (rc) > > + return rc; > > + > > + mutex_lock(&cinode->writers_lock); > > + if (!cinode->writers) > > + set_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > > + cinode->writers++; > > + /* Check to see if we have started servicing an oplock break */ > > + if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) { > > + cinode->writers--; > > + if (cinode->writers == 0) { > > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > > + } > > + mutex_unlock(&cinode->writers_lock); > > + goto start; > > + } > > + mutex_unlock(&cinode->writers_lock); > > + return 0; > > +} > > + > > +void cifs_put_writer(struct cifsInodeInfo *cinode) > > +{ > > + mutex_lock(&cinode->writers_lock); > > + cinode->writers--; > > + if (cinode->writers == 0) { > > + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > > + } > > + mutex_unlock(&cinode->writers_lock); > > +} > > + > > +void cifs_done_oplock_break(struct cifsInodeInfo *cinode) > > +{ > > + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > > + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK); > > +} > > + > > bool > > backup_cred(struct cifs_sb_info *cifs_sb) > > { > > Looks good otherwise, and definitely something we need to fix since > it's a data corruptor. The final version of this should probably go to > stable for that reason... Jeff, I've made the changes you mentioned and have posted the latest version to the list. I did however leave the spinlock writers_lock in there. Sachin Prabhu -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" 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/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 849f613..6d5cf79 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -253,6 +253,11 @@ cifs_alloc_inode(struct super_block *sb) cifs_set_oplock_level(cifs_inode, 0); cifs_inode->delete_pending = false; cifs_inode->invalid_mapping = false; + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cifs_inode->flags); + clear_bit(CIFS_INODE_PENDING_WRITERS, &cifs_inode->flags); + clear_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cifs_inode->flags); + mutex_init(&cifs_inode->writers_lock); + cifs_inode->writers = 0; cifs_inode->vfs_inode.i_blkbits = 14; /* 2**14 = CIFS_MAX_MSGSIZE */ cifs_inode->server_eof = 0; cifs_inode->uniqueid = 0; @@ -731,19 +736,26 @@ static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { struct inode *inode = file_inode(iocb->ki_filp); + struct cifsInodeInfo *cinode = CIFS_I(inode); ssize_t written; int rc; + written = cifs_get_writer(cinode); + if (written) + return written; + written = generic_file_aio_write(iocb, iov, nr_segs, pos); if (CIFS_CACHE_WRITE(CIFS_I(inode))) - return written; + goto out; rc = filemap_fdatawrite(inode->i_mapping); if (rc) cifs_dbg(FYI, "cifs_file_aio_write: %d rc on %p inode\n", rc, inode); +out: + cifs_put_writer(cinode); return written; } diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index f918a99..1a3a88d 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1096,6 +1096,15 @@ struct cifsInodeInfo { unsigned int epoch; /* used to track lease state changes */ bool delete_pending; /* DELETE_ON_CLOSE is set */ bool invalid_mapping; /* pagecache is invalid */ + unsigned long flags; +#define CIFS_INODE_PENDING_OPLOCK_BREAK 0 /* oplock break in progress */ +#define CIFS_INODE_PENDING_WRITERS 1 /* Writing operations in progress */ +#define CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2 2 /* + * We have received a request to + * downgrade oplock to L2 oplock + */ + struct mutex writers_lock; + unsigned int writers; /* Number of writers on this inode */ unsigned long time; /* jiffies of last update of inode */ u64 server_eof; /* current file size on server -- protected by i_lock */ u64 uniqueid; /* server inode number */ diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index 2c29db6..fa41676 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -127,6 +127,9 @@ extern u64 cifs_UnixTimeToNT(struct timespec); extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time, int offset); extern void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock); +extern int cifs_get_writer(struct cifsInodeInfo *cinode); +extern void cifs_put_writer(struct cifsInodeInfo *cinode); +extern void cifs_done_oplock_break(struct cifsInodeInfo *cinode); extern int cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, const unsigned int xid); extern int cifs_push_mandatory_locks(struct cifsFileInfo *cfile); diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 5a5a872..5a94d7b 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -2580,12 +2580,20 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); ssize_t written; + written = cifs_get_writer(cinode); + if (written) + return written; + if (CIFS_CACHE_WRITE(cinode)) { if (cap_unix(tcon->ses) && (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) - && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) - return generic_file_aio_write(iocb, iov, nr_segs, pos); - return cifs_writev(iocb, iov, nr_segs, pos); + && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0)) { + written = generic_file_aio_write( + iocb, iov, nr_segs, pos); + goto out; + } + written = cifs_writev(iocb, iov, nr_segs, pos); + goto out; } /* * For non-oplocked files in strict cache mode we need to write the data @@ -2605,6 +2613,8 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov, inode); cinode->oplock = 0; } +out: + cifs_put_writer(cinode); return written; } @@ -3616,6 +3626,13 @@ static int cifs_launder_page(struct page *page) return rc; } +static int +cifs_oplock_break_wait(void *unused) +{ + schedule(); + return signal_pending(current) ? -ERESTARTSYS : 0; +} + void cifs_oplock_break(struct work_struct *work) { struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo, @@ -3625,6 +3642,14 @@ void cifs_oplock_break(struct work_struct *work) struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); int rc = 0; + wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS, + cifs_oplock_break_wait, TASK_UNINTERRUPTIBLE); + + if (test_bit(CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, &cinode->flags)) + cifs_set_oplock_level(cinode, OPLOCK_READ); + else + cifs_set_oplock_level(cinode, 0); + if (!CIFS_CACHE_WRITE(cinode) && CIFS_CACHE_READ(cinode) && cifs_has_mand_locks(cinode)) { cifs_dbg(FYI, "Reset oplock to None for inode=%p due to mand locks\n", @@ -3661,6 +3686,7 @@ void cifs_oplock_break(struct work_struct *work) cinode); cifs_dbg(FYI, "Oplock release rc = %d\n", rc); } + cifs_done_oplock_break(cinode); } /* diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c index 2f9f379..55b26bd 100644 --- a/fs/cifs/misc.c +++ b/fs/cifs/misc.c @@ -466,8 +466,22 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv) cifs_dbg(FYI, "file id match, oplock break\n"); pCifsInode = CIFS_I(netfile->dentry->d_inode); - cifs_set_oplock_level(pCifsInode, - pSMB->OplockLevel ? OPLOCK_READ : 0); + set_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, + &pCifsInode->flags); + + /* + * Set flag if the server downgrades the oplock + * to L2 else clear. + */ + if (pSMB->OplockLevel) + set_bit( + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, + &pCifsInode->flags); + else + clear_bit( + CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2, + &pCifsInode->flags); + queue_work(cifsiod_wq, &netfile->oplock_break); netfile->oplock_break_cancelled = false; @@ -551,6 +565,62 @@ void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock) cinode->oplock = 0; } +static int +cifs_oplock_break_wait(void *unused) +{ + schedule(); + return signal_pending(current) ? -ERESTARTSYS : 0; +} + +/* + * We wait for oplock breaks to be processed before we attempt to perform + * writes. + */ +int cifs_get_writer(struct cifsInodeInfo *cinode) +{ + int rc; + +start: + rc = wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK, + cifs_oplock_break_wait, TASK_KILLABLE); + if (rc) + return rc; + + mutex_lock(&cinode->writers_lock); + if (!cinode->writers) + set_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); + cinode->writers++; + /* Check to see if we have started servicing an oplock break */ + if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) { + cinode->writers--; + if (cinode->writers == 0) { + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); + } + mutex_unlock(&cinode->writers_lock); + goto start; + } + mutex_unlock(&cinode->writers_lock); + return 0; +} + +void cifs_put_writer(struct cifsInodeInfo *cinode) +{ + mutex_lock(&cinode->writers_lock); + cinode->writers--; + if (cinode->writers == 0) { + clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); + } + mutex_unlock(&cinode->writers_lock); +} + +void cifs_done_oplock_break(struct cifsInodeInfo *cinode) +{ + clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); + wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK); +} + bool backup_cred(struct cifs_sb_info *cifs_sb) {
Problem reported in Red Hat bz 1040329 for strict writes where we cache only when we hold oplock and write direct to the server when we don't. When we receive an oplock break, we first change the oplock value for the inode in cifsInodeInfo->oplock to indicate that we no longer hold the oplock before we enqueue a task to flush changes to the backing device. Once we have completed flushing the changes, we return the oplock to the server. There are 2 ways here where we can have data corruption 1) While we flush changes to the backing device as part of the oplock break, we can have processes write to the file. These writes check for the oplock, find none and attempt to write directly to the server. These direct writes made while we are flushing from cache could be overwritten by data being flushed from the cache causing data corruption. 2) While a thread runs in cifs_strict_writev, the machine could receive and process an oplock break after the thread has checked the oplock and found that it allows us to cache and before we have made changes to the cache. In that case, we end up with a dirty page in cache when we shouldn't have any. This will be flushed later and will overwrite all subsequent writes to the part of the file represented by this page. Before making any writes to the server, we need to confirm that we are not in the process of flushing data to the server and if we are, we should wait until the process is complete before we attempt the write. We should also wait for existing writes to complete before we process an oplock break request which changes oplock values. Signed-off-by: Sachin Prabhu <sprabhu@redhat.com> --- fs/cifs/cifsfs.c | 14 +++++++++- fs/cifs/cifsglob.h | 9 +++++++ fs/cifs/cifsproto.h | 3 +++ fs/cifs/file.c | 32 ++++++++++++++++++++--- fs/cifs/misc.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++-- 5 files changed, 126 insertions(+), 6 deletions(-)