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Date: Tue, 29 Sep 2009 14:15:23 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: Jiaying Zhang <jiayingz@...gle.com>
CC: Andreas Dilger <adilger@....com>, Theodore Tso <tytso@....edu>,
Frank Mayhar <fmayhar@...gle.com>,
Curt Wohlgemuth <curtw@...gle.com>,
ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: Question on fallocate/ftruncate sequence
Jiaying Zhang wrote:
> Sorry for taking so long to finish this. Here is the new patch based on
> Andreas's suggestions. Now the patch clears the EXT4_EOFBLOCKS_FL
> flag when we allocate beyond the maximum allocated block. I also
> made the EOFBLOCKS flag user visible and added the handling
> in ext4_ioctl as Andrea suggested.
I was testing this a bit in xfstests, with test 083 (recently I sent a
patch to the xfs list to let that test run on generic filesystems) which
runs fsstress on a small-ish 100M fs, and that fsstress does space
preallocation (on newer kernels, where the older xfs ioctls are hooked
up to do_fallocate in a generic fashion).
I'm actually seeing more corruption w/ this patch than without it,
though I don't yet see why. I'll double check that it applied properly,
since this was against 2.6.30.5....
Also it strikes me as a little odd to allow clearing of the EOF Flag
from userspace, and the subsequent discarding of the blocks past EOF.
Doesn't truncating to i_size do exactly the same thing, in a more
portable way? Why make a new interface unique to ext4?
-Eric
> Index: linux-2.6.30.5/fs/ext4/inode.c
> ===================================================================
> --- linux-2.6.30.5.orig/fs/ext4/inode.c 2009-08-31 12:08:10.000000000 -0700
> +++ linux-2.6.30.5/fs/ext4/inode.c 2009-09-23 21:42:33.000000000 -0700
> @@ -3973,6 +3973,8 @@ void ext4_truncate(struct inode *inode)
> if (!ext4_can_truncate(inode))
> return;
>
> + inode->i_flags &= ~EXT4_EOFBLOCKS_FL;
> +
> if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
> ei->i_state |= EXT4_STATE_DA_ALLOC_CLOSE;
>
> @@ -4285,8 +4287,8 @@ void ext4_get_inode_flags(struct ext4_in
> {
> unsigned int flags = ei->vfs_inode.i_flags;
>
> - ei->i_flags &= ~(EXT4_SYNC_FL|EXT4_APPEND_FL|
> - EXT4_IMMUTABLE_FL|EXT4_NOATIME_FL|EXT4_DIRSYNC_FL);
> + ei->i_flags &= ~(EXT4_SYNC_FL|EXT4_APPEND_FL|EXT4_IMMUTABLE_FL|
> + EXT4_NOATIME_FL|EXT4_DIRSYNC_FL|EXT4_EOFBLOCKS_FL);
> if (flags & S_SYNC)
> ei->i_flags |= EXT4_SYNC_FL;
> if (flags & S_APPEND)
> @@ -4297,6 +4299,8 @@ void ext4_get_inode_flags(struct ext4_in
> ei->i_flags |= EXT4_NOATIME_FL;
> if (flags & S_DIRSYNC)
> ei->i_flags |= EXT4_DIRSYNC_FL;
> + if (flags & FS_EOFBLOCKS_FL)
> + ei->i_flags |= EXT4_EOFBLOCKS_FL;
> }
> static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
> struct ext4_inode_info *ei)
> @@ -4807,7 +4811,9 @@ int ext4_setattr(struct dentry *dentry,
> }
>
> if (S_ISREG(inode->i_mode) &&
> - attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
> + attr->ia_valid & ATTR_SIZE &&
> + (attr->ia_size < inode->i_size ||
> + (inode->i_flags & EXT4_EOFBLOCKS_FL))) {
> handle_t *handle;
>
> handle = ext4_journal_start(inode, 3);
> @@ -4838,6 +4844,11 @@ int ext4_setattr(struct dentry *dentry,
> goto err_out;
> }
> }
> + if ((inode->i_flags & EXT4_EOFBLOCKS_FL)) {
> + rc = vmtruncate(inode, attr->ia_size);
> + if (rc)
> + goto err_out;
> + }
> }
>
> rc = inode_setattr(inode, attr);
> Index: linux-2.6.30.5/include/linux/fs.h
> ===================================================================
> --- linux-2.6.30.5.orig/include/linux/fs.h 2009-08-31
> 12:08:10.000000000 -0700
> +++ linux-2.6.30.5/include/linux/fs.h 2009-09-10 21:27:30.000000000 -0700
> @@ -343,9 +343,10 @@ struct inodes_stat_t {
> #define FS_TOPDIR_FL 0x00020000 /* Top of directory hierarchies*/
> #define FS_EXTENT_FL 0x00080000 /* Extents */
> #define FS_DIRECTIO_FL 0x00100000 /* Use direct i/o */
> +#define FS_EOFBLOCKS_FL 0x00200000 /* Blocks allocated beyond EOF */
> #define FS_RESERVED_FL 0x80000000 /* reserved for ext2 lib */
>
> -#define FS_FL_USER_VISIBLE 0x0003DFFF /* User visible flags */
> +#define FS_FL_USER_VISIBLE 0x0023DFFF /* User visible flags */
> #define FS_FL_USER_MODIFIABLE 0x000380FF /* User modifiable flags */
>
>
> Index: linux-2.6.30.5/fs/ext4/ext4.h
> ===================================================================
> --- linux-2.6.30.5.orig/fs/ext4/ext4.h 2009-08-31 12:08:10.000000000 -0700
> +++ linux-2.6.30.5/fs/ext4/ext4.h 2009-09-10 21:28:14.000000000 -0700
> @@ -235,9 +235,10 @@ struct flex_groups {
> #define EXT4_HUGE_FILE_FL 0x00040000 /* Set to each huge file */
> #define EXT4_EXTENTS_FL 0x00080000 /* Inode uses extents */
> #define EXT4_EXT_MIGRATE 0x00100000 /* Inode is migrating */
> +#define EXT4_EOFBLOCKS_FL 0x00200000 /* Blocks allocated
> beyond EOF (bit reserved in fs.h) */
> #define EXT4_RESERVED_FL 0x80000000 /* reserved for ext4 lib */
>
> -#define EXT4_FL_USER_VISIBLE 0x000BDFFF /* User visible flags */
> +#define EXT4_FL_USER_VISIBLE 0x002BDFFF /* User visible flags */
> #define EXT4_FL_USER_MODIFIABLE 0x000B80FF /* User modifiable flags */
>
> /* Flags that should be inherited by new inodes from their parent. */
> Index: linux-2.6.30.5/fs/ext4/extents.c
> ===================================================================
> --- linux-2.6.30.5.orig/fs/ext4/extents.c 2009-09-01 18:14:58.000000000 -0700
> +++ linux-2.6.30.5/fs/ext4/extents.c 2009-09-23 22:12:22.000000000 -0700
> @@ -2788,7 +2788,7 @@ int ext4_ext_get_blocks(handle_t *handle
> {
> struct ext4_ext_path *path = NULL;
> struct ext4_extent_header *eh;
> - struct ext4_extent newex, *ex;
> + struct ext4_extent newex, *ex, *last_ex;
> ext4_fsblk_t newblock;
> int err = 0, depth, ret, cache_type;
> unsigned int allocated = 0;
> @@ -2968,6 +2968,14 @@ int ext4_ext_get_blocks(handle_t *handle
> newex.ee_len = cpu_to_le16(ar.len);
> if (create == EXT4_CREATE_UNINITIALIZED_EXT) /* Mark uninitialized */
> ext4_ext_mark_uninitialized(&newex);
> +
> + if (unlikely(inode->i_flags & EXT4_EOFBLOCKS_FL)) {
> + BUG_ON(!eh->eh_entries);
> + last_ex = EXT_LAST_EXTENT(eh);
> + if (iblock + ar.len > le32_to_cpu(last_ex->ee_block)
> + + ext4_ext_get_actual_len(last_ex))
> + inode->i_flags &= ~EXT4_EOFBLOCKS_FL;
> + }
> err = ext4_ext_insert_extent(handle, inode, path, &newex);
> if (err) {
> /* free data blocks we just allocated */
> @@ -3095,6 +3103,13 @@ static void ext4_falloc_update_inode(str
> i_size_write(inode, new_size);
> if (new_size > EXT4_I(inode)->i_disksize)
> ext4_update_i_disksize(inode, new_size);
> + } else {
> + /*
> + * Mark that we allocate beyond EOF so the subsequent truncate
> + * can proceed even if the new size is the same as i_size.
> + */
> + if (new_size > i_size_read(inode))
> + inode->i_flags |= EXT4_EOFBLOCKS_FL;
> }
> }
>
> Index: linux-2.6.30.5/fs/ext4/ioctl.c
> ===================================================================
> --- linux-2.6.30.5.orig/fs/ext4/ioctl.c 2009-08-16 14:19:38.000000000 -0700
> +++ linux-2.6.30.5/fs/ext4/ioctl.c 2009-09-23 22:04:47.000000000 -0700
> @@ -92,6 +92,16 @@ long ext4_ioctl(struct file *filp, unsig
> flags &= ~EXT4_EXTENTS_FL;
> }
>
> + if (flags & EXT4_EOFBLOCKS_FL) {
> + /* we don't support adding EOFBLOCKS flag */
> + if (!(oldflags & EXT4_EOFBLOCKS_FL)) {
> + err = -EOPNOTSUPP;
> + goto flags_out;
> + }
> + } else if (oldflags & EXT4_EOFBLOCKS_FL)
> + /* free the space reserved with fallocate KEEPSIZE */
> + vmtruncate(inode, inode->i_size);
> +
> handle = ext4_journal_start(inode, 1);
> if (IS_ERR(handle)) {
> err = PTR_ERR(handle);
>
>
--
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