On Wed, 26 Dec 2012 19:53:52 +0400
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> that solution has data races and can end up two identical writes to the
> server: when clientCanCacheAll value can be changed during the execution
> of __generic_file_aio_write.
>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
> fs/cifs/cifsfs.c | 1 -
> fs/cifs/cifsglob.h | 1 -
> fs/cifs/file.c | 94 ++++++++++++++++++------------------------------------
> 3 files changed, 31 insertions(+), 65 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index f653835..de7f916 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -228,7 +228,6 @@ cifs_alloc_inode(struct super_block *sb)
> cifs_set_oplock_level(cifs_inode, 0);
> cifs_inode->delete_pending = false;
> cifs_inode->invalid_mapping = false;
> - cifs_inode->leave_pages_clean = false;
> cifs_inode->vfs_inode.i_blkbits = 14; /* 2**14 = CIFS_MAX_MSGSIZE */
> cifs_inode->server_eof = 0;
> cifs_inode->uniqueid = 0;
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index aea1eec..dfab450 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1030,7 +1030,6 @@ struct cifsInodeInfo {
> bool clientCanCacheAll; /* read and writebehind oplock */
> bool delete_pending; /* DELETE_ON_CLOSE is set */
> bool invalid_mapping; /* pagecache is invalid */
> - bool leave_pages_clean; /* protected by i_mutex, not set pages dirty */
> 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/file.c b/fs/cifs/file.c
> index 0a6677b..1b322d0 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2103,15 +2103,7 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
> } else {
> rc = copied;
> pos += copied;
> - /*
> - * When we use strict cache mode and cifs_strict_writev was run
> - * with level II oplock (indicated by leave_pages_clean field of
> - * CIFS_I(inode)), we can leave pages clean - cifs_strict_writev
> - * sent the data to the server itself.
> - */
> - if (!CIFS_I(inode)->leave_pages_clean ||
> - !(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO))
> - set_page_dirty(page);
> + set_page_dirty(page);
> }
>
> if (rc > 0) {
> @@ -2462,8 +2454,8 @@ ssize_t cifs_user_writev(struct kiocb *iocb, const struct iovec *iov,
> }
>
> static ssize_t
> -cifs_pagecache_writev(struct kiocb *iocb, const struct iovec *iov,
> - unsigned long nr_segs, loff_t pos, bool cache_ex)
> +cifs_writev(struct kiocb *iocb, const struct iovec *iov,
> + unsigned long nr_segs, loff_t pos)
> {
> struct file *file = iocb->ki_filp;
> struct cifsFileInfo *cfile = (struct cifsFileInfo *)file->private_data;
> @@ -2485,12 +2477,8 @@ cifs_pagecache_writev(struct kiocb *iocb, const struct iovec *iov,
> server->vals->exclusive_lock_type, NULL,
> CIFS_WRITE_OP)) {
> mutex_lock(&inode->i_mutex);
> - if (!cache_ex)
> - cinode->leave_pages_clean = true;
> rc = __generic_file_aio_write(iocb, iov, nr_segs,
> - &iocb->ki_pos);
> - if (!cache_ex)
> - cinode->leave_pages_clean = false;
> + &iocb->ki_pos);
> mutex_unlock(&inode->i_mutex);
> }
>
> @@ -2517,62 +2505,42 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
> struct cifsFileInfo *cfile = (struct cifsFileInfo *)
> iocb->ki_filp->private_data;
> struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
> - ssize_t written, written2;
> +
> +#ifdef CONFIG_CIFS_SMB2
> /*
> - * We need to store clientCanCacheAll here to prevent race
> - * conditions - this value can be changed during an execution
> - * of generic_file_aio_write. For CIFS it can be changed from
> - * true to false only, but for SMB2 it can be changed both from
> - * true to false and vice versa. So, we can end up with a data
> - * stored in the cache, not marked dirty and not sent to the
> - * server if this value changes its state from false to true
> - * after cifs_write_end.
> + * If we have an oplock for read and want to write a data to the file
> + * we need to store it in the page cache and then push it to the server
> + * to be sure the next read will get a valid data.
> */
> - bool cache_ex = cinode->clientCanCacheAll;
> - bool cache_read = cinode->clientCanCacheRead;
> - int rc;
> - loff_t saved_pos;
> + if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
> + ssize_t written;
> + int rc;
> +
> + written = generic_file_aio_write(iocb, iov, nr_segs, pos);
> + rc = filemap_fdatawrite(inode->i_mapping);
> + if (rc)
> + return (ssize_t)rc;
>
> - if (cache_ex) {
> - if (cap_unix(tcon->ses) &&
> - ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
> - (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
> - tcon->fsUnixInfo.Capability)))
> - return generic_file_aio_write(iocb, iov, nr_segs, pos);
> - return cifs_pagecache_writev(iocb, iov, nr_segs, pos, cache_ex);
> + return written;
> }
> +#endif
>
> /*
> - * For files without exclusive oplock in strict cache mode we need to
> - * write the data to the server exactly from the pos to pos+len-1 rather
> - * than flush all affected pages because it may cause a error with
> - * mandatory locks on these pages but not on the region from pos to
> - * ppos+len-1.
> + * For non-oplocked files in strict cache mode we need to write the data
> + * to the server exactly from the pos to pos+len-1 rather than flush all
> + * affected pages because it may cause a error with mandatory locks on
> + * these pages but not on the region from pos to ppos+len-1.
> */
> - written = cifs_user_writev(iocb, iov, nr_segs, pos);
> - if (!cache_read || written <= 0)
> - return written;
>
> - saved_pos = iocb->ki_pos;
> - iocb->ki_pos = pos;
> - /* we have a read oplock - need to store a data in the page cache */
> + if (!cinode->clientCanCacheAll)
> + return cifs_user_writev(iocb, iov, nr_segs, pos);
> +
> if (cap_unix(tcon->ses) &&
> - ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
> - (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
> - tcon->fsUnixInfo.Capability)))
> - written2 = generic_file_aio_write(iocb, iov, nr_segs, pos);
> - else
> - written2 = cifs_pagecache_writev(iocb, iov, nr_segs, pos,
> - cache_ex);
> - /* errors occured during writing - invalidate the page cache */
> - if (written2 < 0) {
> - rc = cifs_invalidate_mapping(inode);
> - if (rc)
> - written = (ssize_t)rc;
> - else
> - iocb->ki_pos = saved_pos;
> - }
> - return written;
> + (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);
> }
>
> static struct cifs_readdata *
Straightforward...
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
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