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-rw-r--r--fs/read_write.c74
1 files changed, 45 insertions, 29 deletions
diff --git a/fs/read_write.c b/fs/read_write.c
index 179f1c3..dfd1257 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -35,23 +35,45 @@ static inline int unsigned_offsets(struct file *file)
return file->f_mode & FMODE_UNSIGNED_OFFSET;
}
+static loff_t lseek_execute(struct file *file, struct inode *inode,
+ loff_t offset, loff_t maxsize)
+{
+ if (offset < 0 && !unsigned_offsets(file))
+ return -EINVAL;
+ if (offset > maxsize)
+ return -EINVAL;
+
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ file->f_version = 0;
+ }
+ return offset;
+}
+
/**
- * generic_file_llseek_unlocked - lockless generic llseek implementation
+ * generic_file_llseek_size - generic llseek implementation for regular files
* @file: file structure to seek on
* @offset: file offset to seek to
* @origin: type of seek
+ * @size: max size of file system
+ *
+ * This is a variant of generic_file_llseek that allows passing in a custom
+ * file size.
*
- * Updates the file offset to the value specified by @offset and @origin.
- * Locking must be provided by the caller.
+ * Synchronization:
+ * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)
+ * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes.
+ * read/writes behave like SEEK_SET against seeks.
*/
loff_t
-generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
+generic_file_llseek_size(struct file *file, loff_t offset, int origin,
+ loff_t maxsize)
{
struct inode *inode = file->f_mapping->host;
switch (origin) {
case SEEK_END:
- offset += inode->i_size;
+ offset += i_size_read(inode);
break;
case SEEK_CUR:
/*
@@ -62,14 +84,22 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
*/
if (offset == 0)
return file->f_pos;
- offset += file->f_pos;
- break;
+ /*
+ * f_lock protects against read/modify/write race with other
+ * SEEK_CURs. Note that parallel writes and reads behave
+ * like SEEK_SET.
+ */
+ spin_lock(&file->f_lock);
+ offset = lseek_execute(file, inode, file->f_pos + offset,
+ maxsize);
+ spin_unlock(&file->f_lock);
+ return offset;
case SEEK_DATA:
/*
* In the generic case the entire file is data, so as long as
* offset isn't at the end of the file then the offset is data.
*/
- if (offset >= inode->i_size)
+ if (offset >= i_size_read(inode))
return -ENXIO;
break;
case SEEK_HOLE:
@@ -77,26 +107,15 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
* There is a virtual hole at the end of the file, so as long as
* offset isn't i_size or larger, return i_size.
*/
- if (offset >= inode->i_size)
+ if (offset >= i_size_read(inode))
return -ENXIO;
- offset = inode->i_size;
+ offset = i_size_read(inode);
break;
}
- if (offset < 0 && !unsigned_offsets(file))
- return -EINVAL;
- if (offset > inode->i_sb->s_maxbytes)
- return -EINVAL;
-
- /* Special lock needed here? */
- if (offset != file->f_pos) {
- file->f_pos = offset;
- file->f_version = 0;
- }
-
- return offset;
+ return lseek_execute(file, inode, offset, maxsize);
}
-EXPORT_SYMBOL(generic_file_llseek_unlocked);
+EXPORT_SYMBOL(generic_file_llseek_size);
/**
* generic_file_llseek - generic llseek implementation for regular files
@@ -110,13 +129,10 @@ EXPORT_SYMBOL(generic_file_llseek_unlocked);
*/
loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
{
- loff_t rval;
-
- mutex_lock(&file->f_dentry->d_inode->i_mutex);
- rval = generic_file_llseek_unlocked(file, offset, origin);
- mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+ struct inode *inode = file->f_mapping->host;
- return rval;
+ return generic_file_llseek_size(file, offset, origin,
+ inode->i_sb->s_maxbytes);
}
EXPORT_SYMBOL(generic_file_llseek);
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