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Jeff Layton 0463b49e02 netfs: fix test for whether we can skip read when writing beyond EOF 
commit 827a746f40 upstream.

It's not sufficient to skip reading when the pos is beyond the EOF.
There may be data at the head of the page that we need to fill in
before the write.

Add a new helper function that corrects and clarifies the logic of
when we can skip reads, and have it only zero out the part of the page
that won't have data copied in for the write.

Finally, don't set the page Uptodate after zeroing. It's not up to date
since the write data won't have been copied in yet.

[DH made the following changes:

 - Prefixed the new function with "netfs_".

 - Don't call zero_user_segments() for a full-page write.

 - Altered the beyond-last-page check to avoid a DIV instruction and got
   rid of then-redundant zero-length file check.
]

[ Note: this fix is commit 827a746f40 in mainline kernels. The
	original bug was in ceph, but got lifted into the fs/netfs
	library for v5.13. This backport should apply to stable
	kernels v5.10 though v5.12. ]

Fixes: e1b1240c1f ("netfs: Add write_begin helper")
Reported-by: Andrew W Elble <aweits@rit.edu>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: ceph-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20210613233345.113565-1-jlayton@kernel.org/
Link: https://lore.kernel.org/r/162367683365.460125.4467036947364047314.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/162391826758.1173366.11794946719301590013.stgit@warthog.procyon.org.uk/ # v2
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-06-30 08:47:29 -04:00
arch KVM: SVM: Call SEV Guest Decommission if ASID binding fails 2021-06-30 08:47:29 -04:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:13:14 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 11:37:59 +01:00
crypto async_xor: check src_offs is not NULL before updating it 2021-06-16 12:01:40 +02:00
Documentation mm/slub: clarify verification reporting 2021-06-23 14:42:53 +02:00
drivers i2c: robotfuzz-osif: fix control-request directions 2021-06-30 08:47:25 -04:00
fs netfs: fix test for whether we can skip read when writing beyond EOF 2021-06-30 08:47:29 -04:00
include mm, futex: fix shared futex pgoff on shmem huge page 2021-06-30 08:47:29 -04:00
init pid: take a reference when initializing cad_pid 2021-06-10 13:39:26 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-26 12:06:54 +02:00
kernel swiotlb: manipulate orig_addr when tlb_addr has offset 2021-06-30 08:47:29 -04:00
lib locking/lockdep: Improve noinstr vs errors 2021-06-30 08:47:18 -04:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm, futex: fix shared futex pgoff on shmem huge page 2021-06-30 08:47:29 -04:00
net mac80211: handle various extensible elements correctly 2021-06-30 08:47:23 -04:00
samples samples: vfio-mdev: fix error handing in mdpy_fb_probe() 2021-06-10 13:39:15 +02:00
scripts recordmcount: Correct st_shndx handling 2021-06-30 08:47:23 -04:00
security KEYS: trusted: Fix memory leak on object td 2021-05-19 10:12:50 +02:00
sound ASoC: qcom: lpass-cpu: Fix pop noise during audio capture begin 2021-06-23 14:42:49 +02:00
tools KVM: selftests: Fix kvm_check_cap() assertion 2021-06-30 08:47:22 -04:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: do not allow mapping valid but non-reference-counted pages 2021-06-30 08:47:25 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS f2fs: move ioctl interface definitions to separated file 2021-05-19 10:13:00 +02:00
Makefile Linux 5.10.46 2021-06-23 14:42:55 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.