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Date: Mon, 2 Sep 2013 23:28:56 +0900
From: Namjae Jeon <linkinjeon@...il.com>
To: viro@...iv.linux.org.uk, mtk.manpages@...il.com, tytso@....edu,
adilger.kernel@...ger.ca, bpm@....com, elder@...nel.org,
hch@...radead.org, david@...morbit.com
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-ext4@...r.kernel.org, xfs@....sgi.com, a.sangwan@...sung.com,
Namjae Jeon <linkinjeon@...il.com>,
Namjae Jeon <namjae.jeon@...sung.com>
Subject: [PATCH v2 1/7] fs: add new flag(FALLOC_FL_COLLAPSE_RANGE) for fallocate
From: Namjae Jeon <namjae.jeon@...sung.com>
Add new flag(FALLOC_FL_COLLAPSE_RANGE) for fallocate.
updated detailed semantics in comments.
Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@...sung.com>
---
fs/open.c | 24 +++++++++++++++++++++---
include/uapi/linux/falloc.h | 17 +++++++++++++++++
2 files changed, 38 insertions(+), 3 deletions(-)
diff --git a/fs/open.c b/fs/open.c
index 7931f76..85d243a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -225,12 +225,14 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file_inode(file);
long ret;
+ unsigned blksize_mask = (1 << inode->i_blkbits) - 1;
if (offset < 0 || len <= 0)
return -EINVAL;
/* Return error if mode is not supported */
- if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+ if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
+ FALLOC_FL_COLLAPSE_RANGE))
return -EOPNOTSUPP;
/* Punch hole must have keep size set */
@@ -241,8 +243,12 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
- /* It's not possible punch hole on append only file */
- if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
+ /*
+ * It's not possible to punch hole or perform collapse range
+ * on append only file
+ */
+ if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_COLLAPSE_RANGE)
+ && IS_APPEND(inode))
return -EPERM;
if (IS_IMMUTABLE(inode))
@@ -270,6 +276,18 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
return -EFBIG;
+ /*
+ * Collapse range works only on fs block size aligned offsets.
+ * Check if collapse range is contained within (aligned)i_size.
+ * Collapse range can only be used exclusively.
+ */
+ if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
+ (offset & blksize_mask || len & blksize_mask ||
+ mode & ~FALLOC_FL_COLLAPSE_RANGE ||
+ (offset + len >
+ round_up(i_size_read(inode), (blksize_mask + 1)))))
+ return -EINVAL;
+
if (!file->f_op->fallocate)
return -EOPNOTSUPP;
diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 990c4cc..9614b72 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -4,6 +4,23 @@
#define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */
#define FALLOC_FL_PUNCH_HOLE 0x02 /* de-allocates range */
#define FALLOC_FL_NO_HIDE_STALE 0x04 /* reserved codepoint */
+/*
+ * FALLOC_FL_COLLAPSE_RANGE:
+ * This flag works in 2 steps.
+ * Firstly, it deallocates any data blocks present between [offset, offset+len)
+ * This step is same as punch hole and leaves a hole in the place from where
+ * the blocks are removed.
+ * Next, it eliminates the hole created by moving data blocks into it.
+ * For extent based file systems, we achieve this functionality simply by
+ * updating the starting logical offset of each extent which appears beyond
+ * the hole. As this flag works on blocks of filesystem, the offset and len
+ * provided to fallocate should be aligned with block size of filesystem.
+ * The semantics of this flag are:
+ * 1) It should be used exclusively. No other fallocate flag in combination.
+ * 2) Offset and len supplied to fallocate should be aligned with block size.
+ * 3) (offset + len) could not be greater than file size.
+ */
+#define FALLOC_FL_COLLAPSE_RANGE 0x08 /* it does not leave a hole */
#endif /* _UAPI_FALLOC_H_ */
--
1.7.9.5
--
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