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Message-ID: <4F98508A.2040506@redhat.com>
Date: Wed, 25 Apr 2012 14:29:14 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: ext4 development <linux-ext4@...r.kernel.org>
Subject: [PATCH, RFC2] vfs: teach llseek about custom EOF values
This is a pretty-much untested patch which lets ext4 tell the vfs
llseek code that when someone goes to SEEK_END on a dx dir, they should
go out to the max hash value, not to i_size. It also contains changes
to ext4_dir_llseek (from what is upstream) to send the appropriate
max size for dx, non-dx, extent, non-extent, 32-bit, and 64-bit
systems. (!)
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
---
This patch is mutually exclusive to the "remove ext4_dir_llseek"
patch, of course)
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index b867862..1ac06f3 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -312,9 +312,12 @@ static inline loff_t ext4_get_htree_eof(struct file *filp)
/*
- * ext4_dir_llseek() based on generic_file_llseek() to handle both
- * non-htree and htree directories, where the "offset" is in terms
- * of the filename hash value instead of the byte offset.
+ * ext4_dir_llseek() uses generic_file_llseek() routines.
+ * This handles both non-htree and htree directories, where the "offset"
+ * is in terms of the filename hash value instead of the byte offset.
+ *
+ * For htree/dx dirs, the max offset and SEEK_END are both at
+ * ext4_get_htree_eof.
*
* NOTE: offsets obtained *before* ext4_set_inode_flag(dir, EXT4_INODE_INDEX)
* will be invalid once the directory was converted into a dx directory
@@ -322,64 +325,23 @@ static inline loff_t ext4_get_htree_eof(struct file *filp)
loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin)
{
struct inode *inode = file->f_mapping->host;
- loff_t ret = -EINVAL;
int dx_dir = is_dx_dir(inode);
- mutex_lock(&inode->i_mutex);
-
- /* NOTE: relative offsets with dx directories might not work
- * as expected, as it is difficult to figure out the
- * correct offset between dx hashes */
+ if (dx_dir) {
+ loff_t htree_max = ext4_get_htree_eof(file);
- switch (origin) {
- case SEEK_END:
- if (unlikely(offset > 0))
- goto out_err; /* not supported for directories */
+ return generic_file_llseek_size_eof(file, offset, origin,
+ htree_max, htree_max);
+ } else {
+ loff_t maxsize;
- /* so only negative offsets are left, does that have a
- * meaning for directories at all? */
- if (dx_dir)
- offset += ext4_get_htree_eof(file);
+ if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
+ maxsize= EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
else
- offset += inode->i_size;
- break;
- case SEEK_CUR:
- /*
- * Here we special-case the lseek(fd, 0, SEEK_CUR)
- * position-querying operation. Avoid rewriting the "same"
- * f_pos value back to the file because a concurrent read(),
- * write() or lseek() might have altered it
- */
- if (offset == 0) {
- offset = file->f_pos;
- goto out_ok;
- }
-
- offset += file->f_pos;
- break;
- }
-
- if (unlikely(offset < 0))
- goto out_err;
-
- if (!dx_dir) {
- if (offset > inode->i_sb->s_maxbytes)
- goto out_err;
- } else if (offset > ext4_get_htree_eof(file))
- goto out_err;
+ maxsize= inode->i_sb->s_maxbytes;
- /* Special lock needed here? */
- if (offset != file->f_pos) {
- file->f_pos = offset;
- file->f_version = 0;
+ return generic_file_llseek_size(file, offset, origin, maxsize);
}
-
-out_ok:
- ret = offset;
-out_err:
- mutex_unlock(&inode->i_mutex);
-
- return ret;
}
/*
diff --git a/fs/read_write.c b/fs/read_write.c
index ffc99d2..f67c3b7 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -51,14 +51,15 @@ static loff_t lseek_execute(struct file *file, struct inode *inode,
}
/**
- * generic_file_llseek_size - generic llseek implementation for regular files
+ * generic_file_llseek_size_eof - 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
+ * @eof: if > 0, use for SEEK_END position other than i_size_read()
*
* This is a variant of generic_file_llseek that allows passing in a custom
- * file size.
+ * file size and a custom EOF position.
*
* Synchronization:
* SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)
@@ -66,14 +67,17 @@ static loff_t lseek_execute(struct file *file, struct inode *inode,
* read/writes behave like SEEK_SET against seeks.
*/
loff_t
-generic_file_llseek_size(struct file *file, loff_t offset, int origin,
- loff_t maxsize)
+generic_file_llseek_size_eof(struct file *file, loff_t offset, int origin,
+ loff_t maxsize, loff_t eof)
{
struct inode *inode = file->f_mapping->host;
+ if (!eof)
+ eof = i_size_read(inode);
+
switch (origin) {
case SEEK_END:
- offset += i_size_read(inode);
+ offset += eof;
break;
case SEEK_CUR:
/*
@@ -99,7 +103,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int origin,
* 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 >= i_size_read(inode))
+ if (offset >= eof)
return -ENXIO;
break;
case SEEK_HOLE:
@@ -107,14 +111,32 @@ generic_file_llseek_size(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 >= i_size_read(inode))
+ if (offset >= eof)
return -ENXIO;
- offset = i_size_read(inode);
+ offset = eof;
break;
}
return lseek_execute(file, inode, offset, maxsize);
}
+EXPORT_SYMBOL(generic_file_llseek_size_eof);
+
+/**
+ * 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.
+ */
+loff_t
+generic_file_llseek_size(struct file *file, loff_t offset, int origin,
+ loff_t maxsize)
+{
+ return generic_file_llseek_size(file, offset, origin, maxsize, 0);
+}
EXPORT_SYMBOL(generic_file_llseek_size);
/**
@@ -131,8 +153,8 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
{
struct inode *inode = file->f_mapping->host;
- return generic_file_llseek_size(file, offset, origin,
- inode->i_sb->s_maxbytes);
+ return generic_file_llseek_size_eof(file, offset, origin,
+ inode->i_sb->s_maxbytes, 0);
}
EXPORT_SYMBOL(generic_file_llseek);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8de6755..a6ae7a4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2402,6 +2402,8 @@ extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
int origin, loff_t maxsize);
+extern loff_t generic_file_llseek_size_eof(struct file *file, loff_t offset,
+ int origin, loff_t maxsize, loff_t eof);
extern int generic_file_open(struct inode * inode, struct file * filp);
extern int nonseekable_open(struct inode * inode, struct file * filp);
--
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