f2fs: consider fallocated space for SEEK_DATA

If an amount of data are allocated though fallocate and user writes a couple of
data among the space, f2fs should return the data offset made by user when
SEEK_DATA is requested.

For example, (N: NEW_ADDR by fallocate, X: NEW_ADDR by user)
1) fallocate 0 ~ 10MB
f -> N N N N N N N N N N N N ... N

2) write 4KB at 5MB offset
f -> N N N N N X N N N N N N ... N

3) SEEK_DATA from 0 should return 5MB offset

So, this patch adds a routine to search the first dirty page to handle that.
Then, the SEEK_DATA flow skips NEW_ADDR offsets until any dirty page is found.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 41 insertions, 4 deletions

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 31128571e284..b9f4fbf5c07e 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -19,6 +19,7 @@
 #include <linux/compat.h>
 #include <linux/uaccess.h>
 #include <linux/mount.h>
+#include <linux/pagevec.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -194,13 +195,48 @@ out:
         return ret;
 }
 
+static pgoff_t __get_first_dirty_index(struct address_space *mapping,
+                                                pgoff_t pgofs, int whence)
+{
+        struct pagevec pvec;
+        int nr_pages;
+
+        if (whence != SEEK_DATA)
+                return 0;
+
+        /* find first dirty page index */
+        pagevec_init(&pvec, 0);
+        nr_pages = pagevec_lookup_tag(&pvec, mapping, &pgofs, PAGECACHE_TAG_DIRTY, 1);
+        pgofs = nr_pages ? pvec.pages[0]->index: LONG_MAX;
+        pagevec_release(&pvec);
+        return pgofs;
+}
+
+static bool __found_offset(block_t blkaddr, pgoff_t dirty, pgoff_t pgofs,
+                                                        int whence)
+{
+        switch (whence) {
+        case SEEK_DATA:
+                if ((blkaddr == NEW_ADDR && dirty == pgofs) ||
+                        (blkaddr != NEW_ADDR && blkaddr != NULL_ADDR))
+                        return true;
+                break;
+        case SEEK_HOLE:
+                if (blkaddr == NULL_ADDR)
+                        return true;
+                break;
+        }
+        return false;
+}
+
 static loff_t f2fs_seek_block(struct file *file, loff_t offset, int whence)
 {
         struct inode *inode = file->f_mapping->host;
         loff_t maxbytes = inode->i_sb->s_maxbytes;
         struct dnode_of_data dn;
-        pgoff_t pgofs, end_offset;
-        loff_t data_ofs = offset, isize;
+        pgoff_t pgofs, end_offset, dirty;
+        loff_t data_ofs = offset;
+        loff_t isize;
         int err = 0;
 
         mutex_lock(&inode->i_mutex);
@@ -218,6 +254,8 @@ static loff_t f2fs_seek_block(struct file *file, loff_t offset, int whence)
 
         pgofs = (pgoff_t)(offset >> PAGE_CACHE_SHIFT);
 
+        dirty = __get_first_dirty_index(inode->i_mapping, pgofs, whence);
+
         for (; data_ofs < isize; data_ofs = pgofs << PAGE_CACHE_SHIFT) {
                 set_new_dnode(&dn, inode, NULL, NULL, 0);
                 err = get_dnode_of_data(&dn, pgofs, LOOKUP_NODE_RA);
@@ -244,8 +282,7 @@ static loff_t f2fs_seek_block(struct file *file, loff_t offset, int whence)
                         block_t blkaddr;
                         blkaddr = datablock_addr(dn.node_page, dn.ofs_in_node);
 
-                        if ((whence == SEEK_DATA && blkaddr != NULL_ADDR) ||
-                                (whence == SEEK_HOLE && blkaddr == NULL_ADDR)) {
+                        if (__found_offset(blkaddr, dirty, pgofs, whence)) {
                                 f2fs_put_dnode(&dn);
                                 goto found;
                         }