XArray: Document the locking requirement for the xa_state

It wasn't obvious to all readers that it's unsafe to reuse an xa_state
after dropping the xas_lock() or the rcu_read_lock().

Reported-by: C

XArray: Document the locking requirement for the xa_state

It wasn't obvious to all readers that it's unsafe to reuse an xa_state
after dropping the xas_lock() or the rcu_read_lock().

Reported-by: Charan Teja Kalla <charante@codeaurora.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

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XArray: add xas_split

In order to use multi-index entries for huge pages in the page cache, we
need to be able to split a multi-index entry (eg if a file is truncated in
the middle of a huge page en

XArray: add xas_split

In order to use multi-index entries for huge pages in the page cache, we
need to be able to split a multi-index entry (eg if a file is truncated in
the middle of a huge page entry). This version does not support splitting
more than one level of the tree at a time. This is an acceptable
limitation for the page cache as we do not expect to support order-12
pages in the near future.

[akpm@linux-foundation.org: export xas_split_alloc() to modules]
[willy@infradead.org: fix xarray split]
Link: https://lkml.kernel.org/r/20200910175450.GV6583@casper.infradead.org
[willy@infradead.org: fix xarray]
Link: https://lkml.kernel.org/r/20201001233943.GW20115@casper.infradead.org

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Qian Cai <cai@lca.pw>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lkml.kernel.org/r/20200903183029.14930-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

XArray: Add xa_for_each_range

This function supports iterating over a range of an array. Also add
documentation links for xa_for_each_start().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infrade

XArray: Add xa_for_each_range

This function supports iterating over a range of an array. Also add
documentation links for xa_for_each_start().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

show more ...

XArray: Improve documentation of search marks

Move most of the mark-related documentation to its own section to make
it easier to understand. Add clarification that you can't search for
an unset ma

XArray: Improve documentation of search marks

Move most of the mark-related documentation to its own section to make
it easier to understand. Add clarification that you can't search for
an unset mark, and you can't yet search for combinations of marks.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

show more ...

docs: remove :c:func: annotations from xarray.rst

Now that the build system automatically marks up function references, we
don't have to clutter the source files, so take it out.

[Some paragraphs c

docs: remove :c:func: annotations from xarray.rst

Now that the build system automatically marks up function references, we
don't have to clutter the source files, so take it out.

[Some paragraphs could now benefit from refilling, but that was left out to
avoid obscuring the real changes.]

Acked-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

show more ...

XArray: Use xa_cmpxchg to implement xa_reserve

Jason feels this is clearer, and it saves a function and an exported
symbol.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilco

XArray: Use xa_cmpxchg to implement xa_reserve

Jason feels this is clearer, and it saves a function and an exported
symbol.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Add cyclic allocation

This differs slightly from the IDR equivalent in five ways.

1. It can allocate up to UINT_MAX instead of being limited to INT_MAX,
like xa_alloc(). Also like xa_al

XArray: Add cyclic allocation

This differs slightly from the IDR equivalent in five ways.

1. It can allocate up to UINT_MAX instead of being limited to INT_MAX,
like xa_alloc(). Also like xa_alloc(), it will write to the 'id'
pointer before placing the entry in the XArray.
2. The 'next' cursor is allocated separately from the XArray instead
of being part of the IDR. This saves memory for all the users which
do not use the cyclic allocation API and suits some users better.
3. It returns -EBUSY instead of -ENOSPC.
4. It will attempt to wrap back to the minimum value on memory allocation
failure as well as on an -EBUSY error, assuming that a user would
rather allocate a small ID than suffer an ID allocation failure.
5. It reports whether it has wrapped, which is important to some users.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Add support for 1s-based allocation

A lot of places want to allocate IDs starting at 1 instead of 0.
While the xa_alloc() API supports this, it's not very efficient if lots
of IDs are alloca

XArray: Add support for 1s-based allocation

A lot of places want to allocate IDs starting at 1 instead of 0.
While the xa_alloc() API supports this, it's not very efficient if lots
of IDs are allocated, due to having to walk down to the bottom of the
tree to see if ID 1 is available, then all the way over to the next
non-allocated ID. This method marks ID 0 as being occupied which wastes
one slot in the XArray, but preserves xa_empty() as working.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

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XArray: Change xa_insert to return -EBUSY

Userspace translates EEXIST to "File exists" which isn't a very good
error message for the problem. "Device or resource busy" is a better
indication of wha

XArray: Change xa_insert to return -EBUSY

Userspace translates EEXIST to "File exists" which isn't a very good
error message for the problem. "Device or resource busy" is a better
indication of what went wrong.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Honour reserved entries in xa_insert

xa_insert() should treat reserved entries as occupied, not as available.
Also, it should treat requests to insert a NULL pointer as a request
to reserve

XArray: Honour reserved entries in xa_insert

xa_insert() should treat reserved entries as occupied, not as available.
Also, it should treat requests to insert a NULL pointer as a request
to reserve the slot. Add xa_insert_bh() and xa_insert_irq() for
completeness.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Add xa_cmpxchg_irq and xa_cmpxchg_bh

These convenience wrappers match the other _irq and _bh wrappers we
already have. It turns out I'd already open-coded xa_cmpxchg_irq()
in the shmem code

XArray: Add xa_cmpxchg_irq and xa_cmpxchg_bh

These convenience wrappers match the other _irq and _bh wrappers we
already have. It turns out I'd already open-coded xa_cmpxchg_irq()
in the shmem code, so convert that.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Fix Documentation

Minor fixes.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

XArray: Handle NULL pointers differently for allocation

For allocating XArrays, it makes sense to distinguish beteen erasing an
entry and storing NULL. Storing NULL keeps the index allocated with a

XArray: Handle NULL pointers differently for allocation

For allocating XArrays, it makes sense to distinguish beteen erasing an
entry and storing NULL. Storing NULL keeps the index allocated with a
NULL pointer associated with it while xa_erase() frees the index. Some
existing IDR users rely on this ability.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Add xa_store_bh() and xa_store_irq()

These convenience wrappers disable interrupts while taking the spinlock.
A number of drivers would otherwise have to open-code these functions.

Signed-o

XArray: Add xa_store_bh() and xa_store_irq()

These convenience wrappers disable interrupts while taking the spinlock.
A number of drivers would otherwise have to open-code these functions.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Regularise xa_reserve

The xa_reserve() function was a little unusual in that it attempted to
be callable for all kinds of locking scenarios. Make it look like the
other APIs with __xa_reser

XArray: Regularise xa_reserve

The xa_reserve() function was a little unusual in that it attempted to
be callable for all kinds of locking scenarios. Make it look like the
other APIs with __xa_reserve, xa_reserve_bh and xa_reserve_irq variants.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

xarray: Add range store functionality

This version of xa_store_range() really only supports load and store.
Our only user only needs basic load and store functionality, so there's
no need to do the

xarray: Add range store functionality

This version of xa_store_range() really only supports load and store.
Our only user only needs basic load and store functionality, so there's
no need to do the extra work to support marking and overlapping stores
correctly yet.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

xarray: Track free entries in an XArray

Add the optional ability to track which entries in an XArray are free
and provide xa_alloc() to replace most of the functionality of the IDR.

Signed-off-by:

xarray: Track free entries in an XArray

Add the optional ability to track which entries in an XArray are free
and provide xa_alloc() to replace most of the functionality of the IDR.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

xarray: Add xa_reserve and xa_release

This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_s

xarray: Add xa_reserve and xa_release

This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_store().

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

xarray: Add documentation

This is documentation on how to use the XArray, not details about its
internal implementation.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Josef Bacik <j

xarray: Add documentation

This is documentation on how to use the XArray, not details about its
internal implementation.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Josef Bacik <jbacik@fb.com>

show more ...

XArray: add xas_split

In order to use multi-index entries for huge pages in the page cache, we
need to be able to split a multi-index entry (eg if a file is truncated in
the middle o

XArray: add xas_split

In order to use multi-index entries for huge pages in the page cache, we
need to be able to split a multi-index entry (eg if a file is truncated in
the middle of a huge page entry). This version does not support splitting
more than one level of the tree at a time. This is an acceptable
limitation for the page cache as we do not expect to support order-12
pages in the near future.

[akpm@linux-foundation.org: export xas_split_alloc() to modules]
[willy@infradead.org: fix xarray split]
Link: https://lkml.kernel.org/r/20200910175450.GV6583@casper.infradead.org
[willy@infradead.org: fix xarray]
Link: https://lkml.kernel.org/r/20201001233943.GW20115@casper.infradead.org

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Qian Cai <cai@lca.pw>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lkml.kernel.org/r/20200903183029.14930-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

XArray: Add xa_for_each_range

This function supports iterating over a range of an array. Also add
documentation links for xa_for_each_start().

Signed-off-by: Matthew Wilcox (Or

XArray: Add xa_for_each_range

This function supports iterating over a range of an array. Also add
documentation links for xa_for_each_start().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

show more ...

XArray: Improve documentation of search marks

Move most of the mark-related documentation to its own section to make
it easier to understand. Add clarification that you can't search for

XArray: Improve documentation of search marks

Move most of the mark-related documentation to its own section to make
it easier to understand. Add clarification that you can't search for
an unset mark, and you can't yet search for combinations of marks.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

show more ...

docs: remove :c:func: annotations from xarray.rst

Now that the build system automatically marks up function references, we
don't have to clutter the source files, so take it out.

docs: remove :c:func: annotations from xarray.rst

Now that the build system automatically marks up function references, we
don't have to clutter the source files, so take it out.

[Some paragraphs could now benefit from refilling, but that was left out to
avoid obscuring the real changes.]

Acked-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

show more ...

XArray: Use xa_cmpxchg to implement xa_reserve

Jason feels this is clearer, and it saves a function and an exported
symbol.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Sign

XArray: Use xa_cmpxchg to implement xa_reserve

Jason feels this is clearer, and it saves a function and an exported
symbol.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...

XArray: Add cyclic allocation

This differs slightly from the IDR equivalent in five ways.

1. It can allocate up to UINT_MAX instead of being limited to INT_MAX,
like xa_alloc

XArray: Add cyclic allocation

This differs slightly from the IDR equivalent in five ways.

1. It can allocate up to UINT_MAX instead of being limited to INT_MAX,
like xa_alloc(). Also like xa_alloc(), it will write to the 'id'
pointer before placing the entry in the XArray.
2. The 'next' cursor is allocated separately from the XArray instead
of being part of the IDR. This saves memory for all the users which
do not use the cyclic allocation API and suits some users better.
3. It returns -EBUSY instead of -ENOSPC.
4. It will attempt to wrap back to the minimum value on memory allocation
failure as well as on an -EBUSY error, assuming that a user would
rather allocate a small ID than suffer an ID allocation failure.
5. It reports whether it has wrapped, which is important to some users.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

show more ...