switch generic_write_checks() to iocb and iter

... returning -E... upon error and amount of data left in iter after
(possible) truncation upon success.  Note, that normal case gives
a non-zero (positive) return value, so any tests for != 0 _must_ be
updated.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Conflicts:
	fs/ext4/file.c

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index b5b020a..2a9dd37 100644 (file)
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -404,21 +404,16 @@ static ssize_t
 v9fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
        struct file *file = iocb->ki_filp;
-       ssize_t retval = 0;
-       loff_t origin = iocb->ki_pos;
-       size_t count = iov_iter_count(from);
+       ssize_t retval;
+       loff_t origin;
        int err = 0;
 
-       retval = generic_write_checks(file, &origin, &count);
-       if (retval)
+       retval = generic_write_checks(iocb, from);
+       if (retval <= 0)
                return retval;
 
-       iov_iter_truncate(from, count);
-
-       if (!count)
-               return 0;
-
-       retval = p9_client_write(file->private_data, origin, from, &err);
+       origin = iocb->ki_pos;
+       retval = p9_client_write(file->private_data, iocb->ki_pos, from, &err);
        if (retval > 0) {
                struct inode *inode = file_inode(file);
                loff_t i_size;
@@ -428,12 +423,11 @@ v9fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
                if (inode->i_mapping && inode->i_mapping->nrpages)
                        invalidate_inode_pages2_range(inode->i_mapping,
                                                      pg_start, pg_end);
-               origin += retval;
+               iocb->ki_pos += retval;
                i_size = i_size_read(inode);
-               iocb->ki_pos = origin;
-               if (origin > i_size) {
-                       inode_add_bytes(inode, origin - i_size);
-                       i_size_write(inode, origin);
+               if (iocb->ki_pos > i_size) {
+                       inode_add_bytes(inode, iocb->ki_pos - i_size);
+                       i_size_write(inode, iocb->ki_pos);
                }
                return retval;
        }

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 691a84a..c64d11c 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1739,27 +1739,19 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
        u64 start_pos;
        u64 end_pos;
        ssize_t num_written = 0;
-       ssize_t err = 0;
-       size_t count = iov_iter_count(from);
        bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
-       loff_t pos = iocb->ki_pos;
+       ssize_t err;
+       loff_t pos;
+       size_t count;
 
        mutex_lock(&inode->i_mutex);
-
-       current->backing_dev_info = inode_to_bdi(inode);
-       err = generic_write_checks(file, &pos, &count);
-       if (err) {
+       err = generic_write_checks(iocb, from);
+       if (err <= 0) {
                mutex_unlock(&inode->i_mutex);
-               goto out;
-       }
-
-       if (count == 0) {
-               mutex_unlock(&inode->i_mutex);
-               goto out;
+               return err;
        }
 
-       iov_iter_truncate(from, count);
-
+       current->backing_dev_info = inode_to_bdi(inode);
        err = file_remove_suid(file);
        if (err) {
                mutex_unlock(&inode->i_mutex);
@@ -1786,6 +1778,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
         */
        update_time_for_write(inode);
 
+       pos = iocb->ki_pos;
+       count = iov_iter_count(from);
        start_pos = round_down(pos, root->sectorsize);
        if (start_pos > i_size_read(inode)) {
                /* Expand hole size to cover write data, preventing empty gap */

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 7618419..3f0b933 100644 (file)
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -941,9 +941,9 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_osd_client *osdc =
                &ceph_sb_to_client(inode->i_sb)->client->osdc;
-       ssize_t count = iov_iter_count(from), written = 0;
+       ssize_t count, written = 0;
        int err, want, got;
-       loff_t pos = iocb->ki_pos;
+       loff_t pos;
 
        if (ceph_snap(inode) != CEPH_NOSNAP)
                return -EROFS;
@@ -953,14 +953,12 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
        /* We can write back this queue in page reclaim */
        current->backing_dev_info = inode_to_bdi(inode);
 
-       err = generic_write_checks(file, &pos, &count);
-       if (err)
-               goto out;
-
-       if (count == 0)
+       err = generic_write_checks(iocb, from);
+       if (err <= 0)
                goto out;
-       iov_iter_truncate(from, count);
 
+       pos = iocb->ki_pos;
+       count = iov_iter_count(from);
        err = file_remove_suid(file);
        if (err)
                goto out;

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 4202e74..ca2bc54 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2563,7 +2563,6 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
 {
        struct file *file = iocb->ki_filp;
-       size_t len;
        ssize_t total_written = 0;
        struct cifsFileInfo *open_file;
        struct cifs_tcon *tcon;
@@ -2579,16 +2578,10 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
         * write request.
         */
 
-       len = iov_iter_count(from);
-       rc = generic_write_checks(file, &iocb->ki_pos, &len);
-       if (rc)
+       rc = generic_write_checks(iocb, from);
+       if (rc <= 0)
                return rc;
 
-       if (!len)
-               return 0;
-
-       iov_iter_truncate(from, len);
-
        INIT_LIST_HEAD(&wdata_list);
        cifs_sb = CIFS_FILE_SB(file);
        open_file = file->private_data;
@@ -2599,8 +2592,8 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
 
        memcpy(&saved_from, from, sizeof(struct iov_iter));
 
-       rc = cifs_write_from_iter(iocb->ki_pos, len, from, open_file, cifs_sb,
-                                 &wdata_list);
+       rc = cifs_write_from_iter(iocb->ki_pos, iov_iter_count(from), from,
+                                 open_file, cifs_sb, &wdata_list);
 
        /*
         * If at least one write was successfully sent, then discard any rc
@@ -2674,7 +2667,6 @@ cifs_writev(struct kiocb *iocb, struct iov_iter *from)
        struct cifsInodeInfo *cinode = CIFS_I(inode);
        struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server;
        ssize_t rc;
-       size_t count;
 
        /*
         * We need to hold the sem to be sure nobody modifies lock list
@@ -2683,16 +2675,10 @@ cifs_writev(struct kiocb *iocb, struct iov_iter *from)
        down_read(&cinode->lock_sem);
        mutex_lock(&inode->i_mutex);
 
-       count = iov_iter_count(from);
-       rc = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (rc)
+       rc = generic_write_checks(iocb, from);
+       if (rc <= 0)
                goto out;
 
-       if (count == 0)
-               goto out;
-
-       iov_iter_truncate(from, count);
-
        if (!cifs_find_lock_conflict(cfile, iocb->ki_pos, iov_iter_count(from),
                                     server->vals->exclusive_lock_type, NULL,
                                     CIFS_WRITE_OP))

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 42b1fa3..c10785f 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -97,9 +97,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct blk_plug plug;
        int o_direct = io_is_direct(file);
        int overwrite = 0;
-       size_t length = iov_iter_count(from);
        ssize_t ret;
-       loff_t pos;
 
        /*
         * Unaligned direct AIO must be serialized; see comment above
@@ -116,16 +114,10 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        }
 
        mutex_lock(&inode->i_mutex);
-       ret = generic_write_checks(file, &iocb->ki_pos, &length);
-       if (ret)
+       ret = generic_write_checks(iocb, from);
+       if (ret <= 0)
                goto out;
 
-       if (length == 0)
-               goto out;
-
-       iov_iter_truncate(from, length);
-       pos = iocb->ki_pos;
-
        /*
         * If we have encountered a bitmap-format file, the size limit
         * is smaller than s_maxbytes, which is for extent-mapped files.
@@ -133,19 +125,19 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
                struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 
-               if (pos >= sbi->s_bitmap_maxbytes) {
+               if (iocb->ki_pos >= sbi->s_bitmap_maxbytes) {
                        ret = -EFBIG;
                        goto out;
                }
-               iov_iter_truncate(from, sbi->s_bitmap_maxbytes - pos);
+               iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
        }
 
        iocb->private = &overwrite;
        if (o_direct) {
-               length = iov_iter_count(from);
+               size_t length = iov_iter_count(from);
+               loff_t pos = iocb->ki_pos;
                blk_start_plug(&plug);
 
-
                /* check whether we do a DIO overwrite or not */
                if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
                    !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 8c15d0a..b86c8e0 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1145,13 +1145,11 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
-       size_t count = iov_iter_count(from);
        ssize_t written = 0;
        ssize_t written_buffered = 0;
        struct inode *inode = mapping->host;
        ssize_t err;
        loff_t endbyte = 0;
-       loff_t pos = iocb->ki_pos;
 
        if (get_fuse_conn(inode)->writeback_cache) {
                /* Update size (EOF optimization) and mode (SUID clearing) */
@@ -1167,14 +1165,10 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        /* We can write back this queue in page reclaim */
        current->backing_dev_info = inode_to_bdi(inode);
 
-       err = generic_write_checks(file, &pos, &count);
-       if (err)
-               goto out;
-
-       if (count == 0)
+       err = generic_write_checks(iocb, from);
+       if (err <= 0)
                goto out;
 
-       iov_iter_truncate(from, count);
        err = file_remove_suid(file);
        if (err)
                goto out;
@@ -1184,6 +1178,7 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
                goto out;
 
        if (file->f_flags & O_DIRECT) {
+               loff_t pos = iocb->ki_pos;
                written = generic_file_direct_write(iocb, from, pos);
                if (written < 0 || !iov_iter_count(from))
                        goto out;
@@ -1209,9 +1204,9 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
                written += written_buffered;
                iocb->ki_pos = pos + written_buffered;
        } else {
-               written = fuse_perform_write(file, mapping, from, pos);
+               written = fuse_perform_write(file, mapping, from, iocb->ki_pos);
                if (written >= 0)
-                       iocb->ki_pos = pos + written;
+                       iocb->ki_pos += written;
        }
 out:
        current->backing_dev_info = NULL;
@@ -1412,7 +1407,6 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct fuse_io_priv io = { .async = 0, .file = file };
-       size_t count = iov_iter_count(from);
        ssize_t res;
 
        if (is_bad_inode(inode))
@@ -1420,11 +1414,9 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
        /* Don't allow parallel writes to the same file */
        mutex_lock(&inode->i_mutex);
-       res = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (!res) {
-               iov_iter_truncate(from, count);
+       res = generic_write_checks(iocb, from);
+       if (res > 0)
                res = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
-       }
        fuse_invalidate_attr(inode);
        if (res > 0)
                fuse_write_update_size(inode, iocb->ki_pos);

diff --git a/fs/ncpfs/file.c b/fs/ncpfs/file.c
index ab6363b..011324c 100644 (file)
--- a/fs/ncpfs/file.c
+++ b/fs/ncpfs/file.c
@@ -170,20 +170,15 @@ ncp_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        size_t already_written = 0;
-       loff_t pos = iocb->ki_pos;
-       size_t count = iov_iter_count(from);
        size_t bufsize;
        int errno;
        void *bouncebuffer;
+       off_t pos;
 
        ncp_dbg(1, "enter %pD2\n", file);
-       errno = generic_write_checks(file, &pos, &count);
-       if (errno)
+       errno = generic_write_checks(iocb, from);
+       if (errno <= 0)
                return errno;
-       iov_iter_truncate(from, count);
-       
-       if (!count)
-               return 0;
 
        errno = ncp_make_open(inode, O_WRONLY);
        if (errno) {
@@ -201,10 +196,11 @@ ncp_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
                errno = -EIO;   /* -ENOMEM */
                goto outrel;
        }
+       pos = iocb->ki_pos;
        while (iov_iter_count(from)) {
                int written_this_time;
                size_t to_write = min_t(size_t,
-                                     bufsize - ((off_t)pos % bufsize),
+                                     bufsize - (pos % bufsize),
                                      iov_iter_count(from));
 
                if (copy_from_iter(bouncebuffer, to_write, from) != to_write) {

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 5ddd77a..9634189 100644 (file)
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -969,24 +969,19 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
        struct nfs_direct_req *dreq;
        struct nfs_lock_context *l_ctx;
        loff_t end;
-       size_t count = iov_iter_count(iter);
-       end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
-
-       nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 
        dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
-               file, count, (long long) pos);
+               file, iov_iter_count(iter), (long long) iocb->ki_pos);
 
-       result = generic_write_checks(file, &pos, &count);
-       if (result)
+       result = generic_write_checks(iocb, iter);
+       if (result <= 0)
                goto out;
 
-       result = -EINVAL;
-       if ((ssize_t) count < 0)
-               goto out;
-       result = 0;
-       if (!count)
-               goto out;
+       nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES,
+                     iov_iter_count(iter));
+
+       pos = iocb->ki_pos;
+       end = (pos + iov_iter_count(iter) - 1) >> PAGE_CACHE_SHIFT;
 
        mutex_lock(&inode->i_mutex);
 
@@ -1001,7 +996,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
                        goto out_unlock;
        }
 
-       task_io_account_write(count);
+       task_io_account_write(iov_iter_count(iter));
 
        result = -ENOMEM;
        dreq = nfs_direct_req_alloc();
@@ -1009,7 +1004,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
                goto out_unlock;
 
        dreq->inode = inode;
-       dreq->bytes_left = count;
+       dreq->bytes_left = iov_iter_count(iter);
        dreq->io_start = pos;
        dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
        l_ctx = nfs_get_lock_context(dreq->ctx);

diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index cec4ec3..7bb487e 100644 (file)
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -339,17 +339,14 @@ static ssize_t ntfs_prepare_file_for_write(struct kiocb *iocb,
        struct inode *vi = file_inode(file);
        ntfs_inode *base_ni, *ni = NTFS_I(vi);
        ntfs_volume *vol = ni->vol;
-       size_t count = iov_iter_count(from);
 
        ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, pos "
                        "0x%llx, count 0x%zx.", vi->i_ino,
                        (unsigned)le32_to_cpu(ni->type),
-                       (unsigned long long)iocb->ki_pos, count);
-       err = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (unlikely(err))
-               goto out;
-       iov_iter_truncate(from, count);
-       if (count == 0)
+                       (unsigned long long)iocb->ki_pos,
+                       iov_iter_count(from));
+       err = generic_write_checks(iocb, from);
+       if (unlikely(err <= 0))
                goto out;
        /*
         * All checks have passed.  Before we start doing any writing we want

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index fc53ff0..b93919f 100644 (file)
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2250,9 +2250,10 @@ out:
 static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
                                    struct iov_iter *from)
 {
-       int ret, direct_io, appending, rw_level, have_alloc_sem  = 0;
+       int direct_io, appending, rw_level, have_alloc_sem  = 0;
        int can_do_direct, has_refcount = 0;
        ssize_t written = 0;
+       ssize_t ret;
        size_t count = iov_iter_count(from), orig_count;
        loff_t old_size;
        u32 old_clusters;
@@ -2319,13 +2320,14 @@ relock:
                ocfs2_inode_unlock(inode, 1);
        }
 
-       orig_count = count;
-       ret = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (ret < 0) {
-               mlog_errno(ret);
+       orig_count = iov_iter_count(from);
+       ret = generic_write_checks(iocb, from);
+       if (ret <= 0) {
+               if (ret)
+                       mlog_errno(ret);
                goto out;
        }
-       iov_iter_truncate(from, count);
+       count = ret;
 
        can_do_direct = direct_io;
        ret = ocfs2_prepare_inode_for_write(file, iocb->ki_pos, count, appending,
@@ -2349,7 +2351,7 @@ relock:
                rw_level = -1;
 
                direct_io = 0;
-               iov_iter_reexpand(from, count = orig_count);
+               iov_iter_reexpand(from, orig_count);
                goto relock;
        }
 
@@ -2377,7 +2379,7 @@ relock:
                loff_t endbyte;
                ssize_t written_buffered;
                written = generic_file_direct_write(iocb, from, iocb->ki_pos);
-               if (written < 0 || written == count) {
+               if (written < 0 || !iov_iter_count(from)) {
                        ret = written;
                        goto out_dio;
                }
@@ -2385,7 +2387,6 @@ relock:
                /*
                 * for completing the rest of the request.
                 */
-               count -= written;
                written_buffered = generic_perform_write(file, from, iocb->ki_pos);
                /*
                 * If generic_file_buffered_write() returned a synchronous error

diff --git a/fs/udf/file.c b/fs/udf/file.c
index ccab8b7..3de2eda 100644 (file)
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -120,21 +120,15 @@ static ssize_t udf_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        ssize_t retval;
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
-       size_t count = iov_iter_count(from);
        struct udf_inode_info *iinfo = UDF_I(inode);
        int err;
 
        mutex_lock(&inode->i_mutex);
 
-       retval = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (retval)
+       retval = generic_write_checks(iocb, from);
+       if (retval <= 0)
                goto out;
 
-       if (count == 0)
-               goto out;
-
-       iov_iter_truncate(from, count);
-
        down_write(&iinfo->i_data_sem);
        if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
                loff_t end = iocb->ki_pos + iov_iter_count(from);

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index ebde43e..28d1578 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -551,12 +551,12 @@ xfs_file_aio_write_checks(
        struct file             *file = iocb->ki_filp;
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
-       int                     error = 0;
+       ssize_t                 error = 0;
        size_t                  count = iov_iter_count(from);
 
 restart:
-       error = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (error)
+       error = generic_write_checks(iocb, from);
+       if (error <= 0)
                return error;
 
        error = xfs_break_layouts(inode, iolock);
@@ -577,13 +577,13 @@ restart:
                        xfs_rw_iunlock(ip, *iolock);
                        *iolock = XFS_IOLOCK_EXCL;
                        xfs_rw_ilock(ip, *iolock);
+                       iov_iter_reexpand(from, count);
                        goto restart;
                }
                error = xfs_zero_eof(ip, iocb->ki_pos, i_size_read(inode), &zero);
                if (error)
                        return error;
        }
-       iov_iter_truncate(from, count);
 
        /*
         * Updating the timestamps will grab the ilock again from

diff --git a/include/linux/fs.h b/include/linux/fs.h
index c7b21db..b4aa400 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2566,7 +2566,7 @@ extern int sb_min_blocksize(struct super_block *, int);
 
 extern int generic_file_mmap(struct file *, struct vm_area_struct *);
 extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
-int generic_write_checks(struct file *file, loff_t *pos, size_t *count);
+extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);

diff --git a/mm/filemap.c b/mm/filemap.c
index dfc573c..243997a 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2260,36 +2260,38 @@ EXPORT_SYMBOL(read_cache_page_gfp);
  * Returns appropriate error code that caller should return or
  * zero in case that write should be allowed.
  */
-inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count)
+inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 {
+       struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        unsigned long limit = rlimit(RLIMIT_FSIZE);
+       loff_t pos;
 
-        if (unlikely(*pos < 0))
-                return -EINVAL;
+       if (!iov_iter_count(from))
+               return 0;
 
        /* FIXME: this is for backwards compatibility with 2.4 */
        if (file->f_flags & O_APPEND)
-               *pos = i_size_read(inode);
+               iocb->ki_pos = i_size_read(inode);
+
+       pos = iocb->ki_pos;
 
        if (limit != RLIM_INFINITY) {
-               if (*pos >= limit) {
+               if (iocb->ki_pos >= limit) {
                        send_sig(SIGXFSZ, current, 0);
                        return -EFBIG;
                }
-               if (*count > limit - (typeof(limit))*pos)
-                       *count = limit - (typeof(limit))*pos;
+               iov_iter_truncate(from, limit - (unsigned long)pos);
        }
 
        /*
         * LFS rule
         */
-       if (unlikely(*pos + *count > MAX_NON_LFS &&
+       if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
                                !(file->f_flags & O_LARGEFILE))) {
-               if (*pos >= MAX_NON_LFS)
+               if (pos >= MAX_NON_LFS)
                        return -EFBIG;
-               if (*count > MAX_NON_LFS - (unsigned long)*pos)
-                       *count = MAX_NON_LFS - (unsigned long)*pos;
+               iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
        }
 
        /*
@@ -2299,16 +2301,11 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count)
         * exceeded without writing data we send a signal and return EFBIG.
         * Linus frestrict idea will clean these up nicely..
         */
-       if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
-               if (*count || *pos > inode->i_sb->s_maxbytes) {
-                       return -EFBIG;
-               }
-               /* zero-length writes at ->s_maxbytes are OK */
-       }
+       if (unlikely(pos >= inode->i_sb->s_maxbytes))
+               return -EFBIG;
 
-       if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
-               *count = inode->i_sb->s_maxbytes - *pos;
-       return 0;
+       iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
+       return iov_iter_count(from);
 }
 EXPORT_SYMBOL(generic_write_checks);
 
@@ -2618,14 +2615,11 @@ ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        ssize_t ret;
-       size_t count = iov_iter_count(from);
 
        mutex_lock(&inode->i_mutex);
-       ret = generic_write_checks(file, &iocb->ki_pos, &count);
-       if (!ret && count) {
-               iov_iter_truncate(from, count);
+       ret = generic_write_checks(iocb, from);
+       if (ret > 0)
                ret = __generic_file_write_iter(iocb, from);
-       }
        mutex_unlock(&inode->i_mutex);
 
        if (ret > 0) {