AFS: implement basic file write support

Implement support for writing to regular AFS files, including:

 (1) write

 (2) truncate

 (3) fsync, fdatasync

 (4) chmod, chown, chgrp, utime.

AFS writeback attempts to batch writes into as chunks as large as it can manage
up to the point that it writes back 65535 pages in one chunk or it meets a
locked page.

Furthermore, if a page has been written to using a particular key, then should
another write to that page use some other key, the first write will be flushed
before the second is allowed to take place.  If the first write fails due to a
security error, then the page will be scrapped and reread before the second
write takes place.

If a page is dirty and the callback on it is broken by the server, then the
dirty data is not discarded (same behaviour as NFS).

Shared-writable mappings are not supported by this patch.

[akpm@linux-foundation.org: fix a bunch of warnings]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 65 insertions, 1 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 9feb5c59d8fc..a30d4fa768e3 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -21,6 +21,7 @@
 
 #define AFS_CELL_MAX_ADDRS 15
 
+struct pagevec;
 struct afs_call;
 
 typedef enum {
@@ -75,12 +76,15 @@ struct afs_call {
         struct key              *key;           /* security for this call */
         struct afs_server       *server;        /* server affected by incoming CM call */
         void                    *request;       /* request data (first part) */
-        void                    *request2;      /* request data (second part) */
+        struct address_space    *mapping;       /* page set */
+        struct afs_writeback    *wb;            /* writeback being performed */
         void                    *buffer;        /* reply receive buffer */
         void                    *reply;         /* reply buffer (first part) */
         void                    *reply2;        /* reply buffer (second part) */
         void                    *reply3;        /* reply buffer (third part) */
         void                    *reply4;        /* reply buffer (fourth part) */
+        pgoff_t                 first;          /* first page in mapping to deal with */
+        pgoff_t                 last;           /* last page in mapping to deal with */
         enum {                                  /* call state */
                 AFS_CALL_REQUESTING,    /* request is being sent for outgoing call */
                 AFS_CALL_AWAIT_REPLY,   /* awaiting reply to outgoing call */
@@ -97,14 +101,18 @@ struct afs_call {
         unsigned                request_size;   /* size of request data */
         unsigned                reply_max;      /* maximum size of reply */
         unsigned                reply_size;     /* current size of reply */
+        unsigned                first_offset;   /* offset into mapping[first] */
+        unsigned                last_to;        /* amount of mapping[last] */
         unsigned short          offset;         /* offset into received data store */
         unsigned char           unmarshall;     /* unmarshalling phase */
         bool                    incoming;       /* T if incoming call */
+        bool                    send_pages;     /* T if data from mapping should be sent */
         u16                     service_id;     /* RxRPC service ID to call */
         __be16                  port;           /* target UDP port */
         __be32                  operation_ID;   /* operation ID for an incoming call */
         u32                     count;          /* count for use in unmarshalling */
         __be32                  tmp;            /* place to extract temporary data */
+        afs_dataversion_t       store_version;  /* updated version expected from store */
 };
 
 struct afs_call_type {
@@ -124,6 +132,32 @@ struct afs_call_type {
 };
 
 /*
+ * record of an outstanding writeback on a vnode
+ */
+struct afs_writeback {
+        struct list_head        link;           /* link in vnode->writebacks */
+        struct work_struct      writer;         /* work item to perform the writeback */
+        struct afs_vnode        *vnode;         /* vnode to which this write applies */
+        struct key              *key;           /* owner of this write */
+        wait_queue_head_t       waitq;          /* completion and ready wait queue */
+        pgoff_t                 first;          /* first page in batch */
+        pgoff_t                 point;          /* last page in current store op */
+        pgoff_t                 last;           /* last page in batch (inclusive) */
+        unsigned                offset_first;   /* offset into first page of start of write */
+        unsigned                to_last;        /* offset into last page of end of write */
+        int                     num_conflicts;  /* count of conflicting writes in list */
+        int                     usage;
+        bool                    conflicts;      /* T if has dependent conflicts */
+        enum {
+                AFS_WBACK_SYNCING,              /* synchronisation being performed */
+                AFS_WBACK_PENDING,              /* write pending */
+                AFS_WBACK_CONFLICTING,          /* conflicting writes posted */
+                AFS_WBACK_WRITING,              /* writing back */
+                AFS_WBACK_COMPLETE              /* the writeback record has been unlinked */
+        } state __attribute__((packed));
+};
+
+/*
  * AFS superblock private data
  * - there's one superblock per volume
  */
@@ -305,6 +339,7 @@ struct afs_vnode {
         wait_queue_head_t       update_waitq;   /* status fetch waitqueue */
         int                     update_cnt;     /* number of outstanding ops that will update the
                                                  * status */
+        spinlock_t              writeback_lock; /* lock for writebacks */
         spinlock_t              lock;           /* waitqueue/flags lock */
         unsigned long           flags;
 #define AFS_VNODE_CB_BROKEN     0               /* set if vnode's callback was broken */
@@ -316,6 +351,8 @@ struct afs_vnode {
 
         long                    acl_order;      /* ACL check count (callback break count) */
 
+        struct list_head        writebacks;     /* alterations in pagecache that need writing */
+
         /* outstanding callback notification on this file */
         struct rb_node          server_rb;      /* link in server->fs_vnodes */
         struct rb_node          cb_promise;     /* link in server->cb_promises */
@@ -463,6 +500,12 @@ extern int afs_fs_rename(struct afs_server *, struct key *,
                          struct afs_vnode *, const char *,
                          struct afs_vnode *, const char *,
                          const struct afs_wait_mode *);
+extern int afs_fs_store_data(struct afs_server *, struct afs_writeback *,
+                             pgoff_t, pgoff_t, unsigned, unsigned,
+                             const struct afs_wait_mode *);
+extern int afs_fs_setattr(struct afs_server *, struct key *,
+                          struct afs_vnode *, struct iattr *,
+                          const struct afs_wait_mode *);
 
 /*
  * inode.c
@@ -473,6 +516,7 @@ extern struct inode *afs_iget(struct super_block *, struct key *,
 extern void afs_zap_data(struct afs_vnode *);
 extern int afs_validate(struct afs_vnode *, struct key *);
 extern int afs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
+extern int afs_setattr(struct dentry *, struct iattr *);
 extern void afs_clear_inode(struct inode *);
 
 /*
@@ -625,6 +669,9 @@ extern int afs_vnode_symlink(struct afs_vnode *, struct key *, const char *,
                              struct afs_file_status *, struct afs_server **);
 extern int afs_vnode_rename(struct afs_vnode *, struct afs_vnode *,
                             struct key *, const char *, const char *);
+extern int afs_vnode_store_data(struct afs_writeback *, pgoff_t, pgoff_t,
+                                unsigned, unsigned);
+extern int afs_vnode_setattr(struct afs_vnode *, struct key *, struct iattr *);
 
 /*
  * volume.c
@@ -641,6 +688,23 @@ extern struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *);
 extern int afs_volume_release_fileserver(struct afs_vnode *,
                                          struct afs_server *, int);
 
+/*
+ * write.c
+ */
+extern int afs_set_page_dirty(struct page *);
+extern void afs_put_writeback(struct afs_writeback *);
+extern int afs_prepare_write(struct file *, struct page *, unsigned, unsigned);
+extern int afs_commit_write(struct file *, struct page *, unsigned, unsigned);
+extern int afs_writepage(struct page *, struct writeback_control *);
+extern int afs_writepages(struct address_space *, struct writeback_control *);
+extern int afs_write_inode(struct inode *, int);
+extern void afs_pages_written_back(struct afs_vnode *, struct afs_call *);
+extern ssize_t afs_file_write(struct kiocb *, const struct iovec *,
+                              unsigned long, loff_t);
+extern int afs_writeback_all(struct afs_vnode *);
+extern int afs_fsync(struct file *, struct dentry *, int);
+
+
 /*****************************************************************************/
 /*
  * debug tracing