RE: [PATCH RESEND 2/12] xfs: Add support FALLOC_FL_INSERT_RANGE for fallocate

From: Namjae Jeon
Date: Mon Feb 16 2015 - 20:47:21 EST

Hi Dave,

I did totally check your review points.
I will share the patch soon.

Thanks for your review!

> On Tue, Feb 17, 2015 at 12:47:49AM +0900, Namjae Jeon wrote:
> > From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> >
> > This patch implements fallocate's FALLOC_FL_INSERT_RANGE for XFS.
> >
> > 1) Make sure that both offset and len are block size aligned.
> > 2) Update the i_size of inode by len bytes.
> > 3) Compute the file's logical block number against offset. If the computed
> > block number is not the starting block of the extent, split the extent
> > such that the block number is the starting block of the extent.
> > 4) Shift all the extents which are lying bewteen [offset, last allocated extent]
> > towards right by len bytes. This step will make a hole of len bytes
> > at offset.
> >
> > Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> > Signed-off-by: Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
> > Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> > ---
> > fs/xfs/libxfs/xfs_bmap.c | 358 ++++++++++++++++++++++++++++++++++++++++------
> > fs/xfs/libxfs/xfs_bmap.h | 13 +-
> > fs/xfs/xfs_bmap_util.c | 126 +++++++++++-----
> > fs/xfs/xfs_bmap_util.h | 2 +
> > fs/xfs/xfs_file.c | 38 ++++-
> > fs/xfs/xfs_trace.h | 1 +
> > 6 files changed, 455 insertions(+), 83 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> > index 61ec015..6699e53 100644
> > --- a/fs/xfs/libxfs/xfs_bmap.c
> > +++ b/fs/xfs/libxfs/xfs_bmap.c
> > @@ -5518,50 +5518,86 @@ xfs_bmse_shift_one(
> > int *current_ext,
> > struct xfs_bmbt_rec_host *gotp,
> > struct xfs_btree_cur *cur,
> > - int *logflags)
> > + int *logflags,
> > + enum SHIFT_DIRECTION SHIFT)
>
> Please don't shout. ;)
>
> Lower case for types and variables, upper case for the enum values.
> I also think the "shift" variable should be named "direction",
> too, so the code reads "if (direction == SHIFT_LEFT)" and so is
> clearly self documenting...
>
> (only commenting once on this, please change it in other places)
> as well ;)
>
> > {
> > struct xfs_ifork *ifp;
> > xfs_fileoff_t startoff;
> > - struct xfs_bmbt_rec_host *leftp;
> > + struct xfs_bmbt_rec_host *contp;
> > struct xfs_bmbt_irec got;
> > - struct xfs_bmbt_irec left;
> > + struct xfs_bmbt_irec cont;
>
> Not sure what "cont" is short for. It's used as the "adjacent
> extent" record, so that would be a better name IMO.
>
> > int error;
> > int i;
> > + int total_extents;
> >
> > ifp = XFS_IFORK_PTR(ip, whichfork);
> > + total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
> >
> > xfs_bmbt_get_all(gotp, &got);
> > - startoff = got.br_startoff - offset_shift_fsb;
> >
> > /* delalloc extents should be prevented by caller */
> > XFS_WANT_CORRUPTED_RETURN(!isnullstartblock(got.br_startblock));
> >
> > - /*
> > - * Check for merge if we've got an extent to the left, otherwise make
> > - * sure there's enough room at the start of the file for the shift.
> > - */
> > - if (*current_ext) {
> > - /* grab the left extent and check for a large enough hole */
> > - leftp = xfs_iext_get_ext(ifp, *current_ext - 1);
> > - xfs_bmbt_get_all(leftp, &left);
> > + if (SHIFT == SHIFT_LEFT) {
> > + startoff = got.br_startoff - offset_shift_fsb;
> >
> > - if (startoff < left.br_startoff + left.br_blockcount)
> > + /*
> > + * Check for merge if we've got an extent to the left,
> > + * otherwise make sure there's enough room at the start
> > + * of the file for the shift.
> > + */
> > + if (*current_ext) {
> > + /*
> > + * grab the left extent and check for a large
> > + * enough hole.
> > + */
> > + contp = xfs_iext_get_ext(ifp, *current_ext - 1);
> > + xfs_bmbt_get_all(contp, &cont);
> > +
> > + if (startoff < cont.br_startoff + cont.br_blockcount)
> > + return -EINVAL;
> > +
> > + /* check whether to merge the extent or shift it down */
> > + if (xfs_bmse_can_merge(&cont, &got, offset_shift_fsb)) {
> > + return xfs_bmse_merge(ip, whichfork,
> > + offset_shift_fsb,
> > + *current_ext, gotp, contp,
> > + cur, logflags);
> > + }
> > + } else if (got.br_startoff < offset_shift_fsb)
> > return -EINVAL;
>
> This would be better written:
>
> if (!*current_ext) {
> if (got.br_startoff < offset_shift_fsb)
> return -EINVAL;
> goto update_current_ext;
> }
>
> and then the rest of the code in the shift left branch can drop a
> level of indent and hence become less congested and easier to read.
>
>
> > + } else {
> > + startoff = got.br_startoff + offset_shift_fsb;
> > + /*
> > + * If this is not the last extent in the file, make sure there's
> > + * enough room between current extent and next extent for
> > + * accommodating the shift.
> > + */
> > + if (*current_ext < (total_extents - 1)) {
> > + contp = xfs_iext_get_ext(ifp, *current_ext + 1);
> > + xfs_bmbt_get_all(contp, &cont);
> > + if (startoff + got.br_blockcount > cont.br_startoff)
> > + return -EINVAL;
> >
> > - /* check whether to merge the extent or shift it down */
> > - if (xfs_bmse_can_merge(&left, &got, offset_shift_fsb)) {
> > - return xfs_bmse_merge(ip, whichfork, offset_shift_fsb,
> > - *current_ext, gotp, leftp, cur,
> > - logflags);
> > + /*
> > + * Unlike a left shift (which involves a hole punch),
> > + * a right shift does not modify extent neighbors
> > + * in any way. We should never find mergeable extents
> > + * in this scenario. Check anyways and warn if we
> > + * encounter two extents that could be one.
> > + */
> > + if (xfs_bmse_can_merge(&got, &cont, offset_shift_fsb))
> > + WARN_ON_ONCE(1);
> > }
>
> Similarly:
> /* nothing to move if this is the last extent */
> if (*current_ext >= total_extents)
> goto update_current_ext;
>
> > - } else if (got.br_startoff < offset_shift_fsb)
> > - return -EINVAL;
> > -
> > + }
> > /*
> > * Increment the extent index for the next iteration, update the start
> > * offset of the in-core extent and update the btree if applicable.
> > */
> > - (*current_ext)++;
>
> update_current_ext:
> > + if (SHIFT == SHIFT_LEFT)
> > + (*current_ext)++;
> > + else
> > + (*current_ext)--;
> > xfs_bmbt_set_startoff(gotp, startoff);
> > *logflags |= XFS_ILOG_CORE;
> > if (!cur) {
> > @@ -5581,10 +5617,10 @@ xfs_bmse_shift_one(
> > }
> >
> > /*
> > - * Shift extent records to the left to cover a hole.
> > + * Shift extent records to the left/right to cover/create a hole.
> > *
> > * The maximum number of extents to be shifted in a single operation is
> > - * @num_exts. @start_fsb specifies the file offset to start the shift and the
> > + * @num_exts. @stop_fsb specifies the file offset at which to stop shift and the
> > * file offset where we've left off is returned in @next_fsb. @offset_shift_fsb
> > * is the length by which each extent is shifted. If there is no hole to shift
> > * the extents into, this will be considered invalid operation and we abort
> > @@ -5594,12 +5630,13 @@ int
> > xfs_bmap_shift_extents(
> > struct xfs_trans *tp,
> > struct xfs_inode *ip,
> > - xfs_fileoff_t start_fsb,
> > + xfs_fileoff_t *next_fsb,
> > xfs_fileoff_t offset_shift_fsb,
> > int *done,
> > - xfs_fileoff_t *next_fsb,
> > + xfs_fileoff_t stop_fsb,
> > xfs_fsblock_t *firstblock,
> > struct xfs_bmap_free *flist,
> > + enum SHIFT_DIRECTION SHIFT,
> > int num_exts)
> > {
> > struct xfs_btree_cur *cur = NULL;
> > @@ -5609,10 +5646,11 @@ xfs_bmap_shift_extents(
> > struct xfs_ifork *ifp;
> > xfs_extnum_t nexts = 0;
> > xfs_extnum_t current_ext;
> > + xfs_extnum_t total_extents;
> > + xfs_extnum_t stop_extent;
> > int error = 0;
> > int whichfork = XFS_DATA_FORK;
> > int logflags = 0;
> > - int total_extents;
> >
> > if (unlikely(XFS_TEST_ERROR(
> > (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
> > @@ -5628,6 +5666,7 @@ xfs_bmap_shift_extents(
> >
> > ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
> > ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> > + ASSERT(SHIFT == SHIFT_LEFT || SHIFT == SHIFT_RIGHT);
> >
> > ifp = XFS_IFORK_PTR(ip, whichfork);
> > if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> > @@ -5645,43 +5684,85 @@ xfs_bmap_shift_extents(
> > }
> >
> > /*
> > + * There may be delalloc extents in the data fork before the range we
> > + * are collapsing out, so we cannot use the count of real extents here.
> > + * Instead we have to calculate it from the incore fork.
> > + */
> > + total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
> > + if (total_extents == 0) {
> > + *done = 1;
> > + goto del_cursor;
> > + }
> > +
> > + /*
> > + * In case of first right shift, we need to initialize next_fsb
> > + */
> > + if (*next_fsb == NULLFSBLOCK) {
> > + ASSERT(SHIFT == SHIFT_RIGHT);
>
> This should be at the top of the function. i.e.
>
> ASSERT(*next_fsb != NULLFSBLOCK || direction == SHIFT_RIGHT)
>
> > + gotp = xfs_iext_get_ext(ifp, total_extents - 1);
> > + xfs_bmbt_get_all(gotp, &got);
> > + *next_fsb = got.br_startoff;
> > + if (stop_fsb > *next_fsb) {
> > + *done = 1;
> > + goto del_cursor;
> > + }
> > + }
> > +
> > + /* Lookup the extent index at which we have to stop */
> > + if (SHIFT == SHIFT_RIGHT) {
> > + gotp = xfs_iext_bno_to_ext(ifp, stop_fsb, &stop_extent);
> > + /* Make stop_extent exclusive of shift range */
> > + stop_extent--;
> > + } else
> > + stop_extent = total_extents;
> > +
> > + /*
> > * Look up the extent index for the fsb where we start shifting. We can
> > * henceforth iterate with current_ext as extent list changes are locked
> > * out via ilock.
> > *
> > * gotp can be null in 2 cases: 1) if there are no extents or 2)
> > - * start_fsb lies in a hole beyond which there are no extents. Either
> > + * *next_fsb lies in a hole beyond which there are no extents. Either
> > * way, we are done.
> > */
> > - gotp = xfs_iext_bno_to_ext(ifp, start_fsb, &current_ext);
> > + gotp = xfs_iext_bno_to_ext(ifp, *next_fsb, &current_ext);
> > if (!gotp) {
> > *done = 1;
> > goto del_cursor;
> > }
> >
> > - /*
> > - * There may be delalloc extents in the data fork before the range we
> > - * are collapsing out, so we cannot use the count of real extents here.
> > - * Instead we have to calculate it from the incore fork.
> > - */
> > - total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
> > - while (nexts++ < num_exts && current_ext < total_extents) {
> > + /* some sanity checking before we finally start shifting extents */
> > + if ((SHIFT == SHIFT_LEFT && current_ext >= stop_extent) ||
> > + (SHIFT == SHIFT_RIGHT && current_ext <= stop_extent)) {
> > + error = EIO;
>
> error = -EIO;
>
> > + goto del_cursor;
> > + }
> > +
> > + while (nexts++ < num_exts) {
> > error = xfs_bmse_shift_one(ip, whichfork, offset_shift_fsb,
> > - &current_ext, gotp, cur, &logflags);
> > + &current_ext, gotp, cur, &logflags,
> > + SHIFT);
> > if (error)
> > goto del_cursor;
> > + /*
> > + * In case there was an extent merge after shifting extent,
> > + * extent numbers would change.
> > + * Update total extent count and grab the next record.
> > + */
>
> /*
> * If there was an extent merge during the shift, the extent
> * count can change. Update the total and grade the next record.
> */
>
> > + if (SHIFT == SHIFT_LEFT) {
> > + total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
> > + stop_extent = total_extents;
> > + }
> >
> > - /* update total extent count and grab the next record */
> > - total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
> > - if (current_ext >= total_extents)
> > + if (current_ext == stop_extent) {
> > + *done = 1;
> > + *next_fsb = NULLFSBLOCK;
> > break;
> > + }
> > gotp = xfs_iext_get_ext(ifp, current_ext);
> > }
> >
> > - /* Check if we are done */
> > - if (current_ext == total_extents) {
> > - *done = 1;
> > - } else if (next_fsb) {
> > + if (!*done) {
> > xfs_bmbt_get_all(gotp, &got);
> > *next_fsb = got.br_startoff;
> > }
> > @@ -5696,3 +5777,192 @@ del_cursor:
> >
> > return error;
> > }
> > +
> > +/*
> > + * Splits an extent into two extents at split_fsb block that it is
> > + * the first block of the current_ext. @current_ext is a target extent
> > + * to be split. @split_fsb is a block where the extents is split.
> > + * If split_fsb lies in a hole or the first block of extents, just return 0.
> > + */
> > +STATIC int
> > +xfs_bmap_split_extent_at(
> > + struct xfs_trans *tp,
> > + struct xfs_inode *ip,
> > + xfs_fileoff_t split_fsb,
> > + xfs_fsblock_t *firstfsb,
> > + struct xfs_bmap_free *free_list)
> > +{
> > + int whichfork = XFS_DATA_FORK;
> > + struct xfs_btree_cur *cur = NULL;
> > + struct xfs_bmbt_rec_host *gotp;
> > + struct xfs_bmbt_irec got;
> > + struct xfs_bmbt_irec new; /* split extent */
> > + struct xfs_mount *mp = ip->i_mount;
> > + struct xfs_ifork *ifp;
> > + xfs_fsblock_t gotblkcnt; /* new block count for got */
> > + xfs_extnum_t current_ext;
> > + int error = 0;
> > + int logflags = 0;
> > + int i = 0;
> > +
> > + if (unlikely(XFS_TEST_ERROR(
> > + (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
> > + XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
> > + mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
> > + XFS_ERROR_REPORT("xfs_bmap_split_extent_at",
> > + XFS_ERRLEVEL_LOW, mp);
> > + return -EFSCORRUPTED;
> > + }
> > +
> > + if (XFS_FORCED_SHUTDOWN(mp))
> > + return -EIO;
> > +
> > + ifp = XFS_IFORK_PTR(ip, whichfork);
> > + if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> > + /* Read in all the extents */
> > + error = xfs_iread_extents(tp, ip, whichfork);
> > + if (error)
> > + return error;
> > + }
> > +
> > + gotp = xfs_iext_bno_to_ext(ifp, split_fsb, &current_ext);
> > + /*
> > + * gotp can be null in 2 cases: 1) if there are no extents
> > + * or 2) split_fsb lies in a hole beyond which there are
> > + * no extents. Either way, we are done.
> > + */
> > + if (!gotp)
> > + return 0;
>
> Comment can go before the call to xfs_iext_bno_to_ext().
>
> > +
> > + xfs_bmbt_get_all(gotp, &got);
> > +
> > + /*
> > + * Check split_fsb lies in a hole or the start boundary offset
> > + * of the extent.
> > + */
> > + if (got.br_startoff >= split_fsb)
> > + return 0;
> > +
> > + gotblkcnt = split_fsb - got.br_startoff;
> > + new.br_startoff = split_fsb;
> > + new.br_startblock = got.br_startblock + gotblkcnt;
> > + new.br_blockcount = got.br_blockcount - gotblkcnt;
> > + new.br_state = got.br_state;
> > +
> > + if (ifp->if_flags & XFS_IFBROOT) {
> > + cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
> > + cur->bc_private.b.firstblock = *firstfsb;
> > + cur->bc_private.b.flist = free_list;
> > + cur->bc_private.b.flags = 0;
> > + }
> > +
> > + if (cur) {
>
> No need to close the XFS_IFBROOT branch and then check for cur;
> we just allocated it inside the XFS_IFBROOT branch!
>
> > + error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
> > + got.br_startblock,
> > + got.br_blockcount,
> > + &i);
> > + if (error)
> > + goto del_cursor;
> > + XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> > + }
>
> ....
>
> > @@ -1427,20 +1429,23 @@ xfs_collapse_file_space(
> >
> > /*
> > * Writeback and invalidate cache for the remainder of the file as we're
> > - * about to shift down every extent from the collapse range to EOF. The
> > - * free of the collapse range above might have already done some of
> > - * this, but we shouldn't rely on it to do anything outside of the range
> > - * that was freed.
> > + * about to shift down every extent from offset to EOF.
> > */
> > error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
> > - offset + len, -1);
> > + offset, -1);
> > if (error)
> > return error;
> > error = invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
> > - (offset + len) >> PAGE_CACHE_SHIFT, -1);
> > + offset >> PAGE_CACHE_SHIFT, -1);
> > if (error)
> > return error;
> >
> > + if (SHIFT == SHIFT_RIGHT) {
> > + error = xfs_bmap_split_extent(ip, stop_fsb);
> > + if (error)
> > + return error;
> > + }
>
> This needs a comment explaining why we are splitting an extent here.
>
> > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> > index 1cdba95..222a91a 100644
> > --- a/fs/xfs/xfs_file.c
> > +++ b/fs/xfs/xfs_file.c
> > @@ -823,11 +823,13 @@ xfs_file_fallocate(
> > long error;
> > enum xfs_prealloc_flags flags = 0;
> > loff_t new_size = 0;
> > + int do_file_insert = 0;
>
> bool rather than int.
>
> >
> > if (!S_ISREG(inode->i_mode))
> > return -EINVAL;
> > if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
> > - FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
> > + FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
> > + FALLOC_FL_INSERT_RANGE))
> > return -EOPNOTSUPP;
>
> This should use a local define before the function such as:
>
> #define XFS_FALLOC_FL_SUPPORTED \
> (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
> FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | \
> FALLOC_FL_INSERT_RANGE)
>
> This is similar to how we define supported checks for FIEMAP
> operations in xfs_vn_fiemap().
>
> >
> > xfs_ilock(ip, XFS_IOLOCK_EXCL);
> > @@ -857,6 +859,28 @@ xfs_file_fallocate(
> > error = xfs_collapse_file_space(ip, offset, len);
> > if (error)
> > goto out_unlock;
> > + } else if (mode & FALLOC_FL_INSERT_RANGE) {
> > + unsigned blksize_mask = (1 << inode->i_blkbits) - 1;
> > +
> > + if (offset & blksize_mask || len & blksize_mask) {
> > + error = -EINVAL;
> > + goto out_unlock;
> > + }
> > +
> > + /* Check for wrap through zero */
> > + if (inode->i_size + len > inode->i_sb->s_maxbytes) {
> > + error = -EFBIG;
> > + goto out_unlock;
> > + }
>
> At first I thought that was a duplicate check of what is in
> vfs_fallocate() (i.e. off + len > s_maxbytes). Can you change the
> comment to read something like:
>
> /* check the new inode size does not wrap through zero */
>
> > +
> > + /* Offset should be less than i_size */
> > + if (offset >= i_size_read(inode)) {
> > + error = -EINVAL;
> > + goto out_unlock;
> > + }
> > +
> > + new_size = i_size_read(inode) + len;
> > + do_file_insert = 1;
>
> Why do you use inode->i_size onthe wrap check, yet i_size_read()
> twice here?
>
> > } else {
> > flags |= XFS_PREALLOC_SET;
> >
> > @@ -891,8 +915,20 @@ xfs_file_fallocate(
> > iattr.ia_valid = ATTR_SIZE;
> > iattr.ia_size = new_size;
> > error = xfs_setattr_size(ip, &iattr);
> > + if (error)
> > + goto out_unlock;
> > }
> >
> > + /*
> > + * Some operations are performed after the inode size is updated. For
> > + * example, insert range expands the address space of the file, shifts
> > + * all subsequent extents to create a hole inside the file. Updating
> > + * the size first ensures that shifted extents aren't left hanging
> > + * past EOF in the event of a crash or failure.
> > + */
>
> /*
> * Perform hole insertion now that the file size has been
> * updated so that if we crash during the operation we don't
> * leave shifted extents past EOF and hence losing access to
> * the data that is contained within them.
> */
> > + if (do_file_insert)
> > + error = xfs_insert_file_space(ip, offset, len);
> > +
> > out_unlock:
> > xfs_iunlock(ip, XFS_IOLOCK_EXCL);
> > return error;
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx

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