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Subject[PATCH] fat: Editions to support fat_fallocate()
Date
From: Steven Cavanagh <steven.cavanagh@secretlab.ca>

Added support for fallocate for a msdos fat driver. This allows
preallocation of clusters to an inode before writes to reduce
file fragmentation

Signed-off-by: Steven.Cavanagh <steven.cavanagh@secretlab.ca>
---
fs/fat/file.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 45 insertions(+), 0 deletions(-)
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 69a83b5..f753c6a 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -15,6 +15,7 @@ #include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
+#include <linux/falloc.h>

int fat_generic_ioctl(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
@@ -312,8 +313,52 @@ int fat_getattr(struct vfsmount *mnt, st
}
EXPORT_SYMBOL_GPL(fat_getattr);

+/*
+ * preallocate space for a file. This implements fat fallocate inode
+ * operation, which gets called from sys_fallocate system call. User
+ * space requests len bytes at offset.
+ */
+long fat_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
+{
+ int ret = 0;
+ loff_t filesize = inode->i_size;
+
+ /* preallocation to directories is currently not supported */
+ if (S_ISDIR(inode->i_mode)) {
+ printk(KERN_ERR
+ "fat_fallocate(): Directory prealloc not supported\n");
+ return -ENODEV;
+ }
+
+ if ((offset + len) <= MSDOS_I(inode)->mmu_private) {
+ printk(KERN_INFO
+ "fat_fallocate():Blocks already allocated\n");
+ return 0;
+ }
+
+ if ((offset + len) > MSDOS_I(inode)->mmu_private) {
+
+ mutex_lock(&inode->i_mutex);
+ ret = fat_cont_expand(inode, (offset + len));
+ if (ret) {
+ printk(KERN_ERR
+ "fat_fallocate():fat_cont_expand() error\n");
+ mutex_unlock(&inode->i_mutex);
+ return ret;
+ }
+ mutex_unlock(&inode->i_mutex);
+ }
+ if (mode & FALLOC_FL_KEEP_SIZE) {
+ mutex_lock(&inode->i_mutex);
+ i_size_write(inode, filesize);
+ mutex_unlock(&inode->i_mutex);
+ }
+ return ret;
+}
+
const struct inode_operations fat_file_inode_operations = {
.truncate = fat_truncate,
.setattr = fat_notify_change,
.getattr = fat_getattr,
+ .fallocate = fat_fallocate,
};

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