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-rw-r--r--fs/fat/file.c61
1 files changed, 61 insertions, 0 deletions
diff --git a/fs/fat/file.c b/fs/fat/file.c
index a08f103..43d3475 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -14,8 +14,12 @@
#include <linux/backing-dev.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
+#include <linux/falloc.h>
#include "fat.h"
+static long fat_fallocate(struct file *file, int mode,
+ loff_t offset, loff_t len);
+
static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
{
u32 attr;
@@ -177,6 +181,7 @@ const struct file_operations fat_file_operations = {
#endif
.fsync = fat_file_fsync,
.splice_read = generic_file_splice_read,
+ .fallocate = fat_fallocate,
};
static int fat_cont_expand(struct inode *inode, loff_t size)
@@ -215,6 +220,62 @@ out:
return err;
}
+/*
+ * Preallocate space for a file. This implements fat's fallocate file
+ * operation, which gets called from sys_fallocate system call. User
+ * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
+ * we just allocate clusters without zeroing them out. Otherwise we
+ * allocate and zero out clusters via an expanding truncate.
+ */
+static long fat_fallocate(struct file *file, int mode,
+ loff_t offset, loff_t len)
+{
+ int nr_cluster; /* Number of clusters to be allocated */
+ loff_t mm_bytes; /* Number of bytes to be allocated for file */
+ loff_t ondisksize; /* block aligned on-disk size in bytes*/
+ struct inode *inode = file->f_mapping->host;
+ struct super_block *sb = inode->i_sb;
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ int err = 0;
+
+ /* No support for hole punch or other fallocate flags. */
+ if (mode & ~FALLOC_FL_KEEP_SIZE)
+ return -EOPNOTSUPP;
+
+ /* No support for dir */
+ if (!S_ISREG(inode->i_mode))
+ return -EOPNOTSUPP;
+
+ mutex_lock(&inode->i_mutex);
+ if (mode & FALLOC_FL_KEEP_SIZE) {
+ ondisksize = inode->i_blocks << 9;
+ if ((offset + len) <= ondisksize)
+ goto error;
+
+ /* First compute the number of clusters to be allocated */
+ mm_bytes = offset + len - ondisksize;
+ nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
+ sbi->cluster_bits;
+
+ /* Start the allocation.We are not zeroing out the clusters */
+ while (nr_cluster-- > 0) {
+ err = fat_add_cluster(inode);
+ if (err)
+ goto error;
+ }
+ } else {
+ if ((offset + len) <= i_size_read(inode))
+ goto error;
+
+ /* This is just an expanding truncate */
+ err = fat_cont_expand(inode, (offset + len));
+ }
+
+error:
+ mutex_unlock(&inode->i_mutex);
+ return err;
+}
+
/* Free all clusters after the skip'th cluster. */
static int fat_free(struct inode *inode, int skip)
{
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